update to .net 6

- global usings
- file-scope namespaces
- update drone image tag

.drone.yml

@@ -4,7 +4,7 @@ name: run
 
 steps:
   - name: run
-    image: mcr.microsoft.com/dotnet/sdk:latest
+    image: mcr.microsoft.com/dotnet/sdk:6.0
     commands:
       - dotnet test
       - dotnet run --project aoc2020/aoc2020.csproj

LICENSE

@@ -1,4 +1,4 @@
-MIT License Copyright (c) <year> <copyright holders>
+MIT License Copyright (c) 2020 Ben Harris
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

aoc2020.test/DayTests.cs

@@ -1,62 +1,60 @@
-using System;
+using System.Diagnostics;
-using System.Diagnostics;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-namespace aoc2020.test
+namespace aoc2020.test;
+
+[TestClass]
+public class DayTests
 {
-    [TestClass]
+    [DataTestMethod]
-    public class DayTests
+    [DataRow(typeof(Day01), "751776", "42275090")]
+    [DataRow(typeof(Day02), "556", "605")]
+    [DataRow(typeof(Day03), "189", "1718180100")]
+    [DataRow(typeof(Day04), "247", "145")]
+    [DataRow(typeof(Day05), "878", "504")]
+    [DataRow(typeof(Day06), "6273", "3254")]
+    [DataRow(typeof(Day07), "169", "82372")]
+    [DataRow(typeof(Day08), "1654", "833")]
+    [DataRow(typeof(Day09), "138879426", "23761694")]
+    [DataRow(typeof(Day10), "1980", "4628074479616")]
+    [DataRow(typeof(Day11), "2303", "2057")]
+    [DataRow(typeof(Day12), "1710", "62045")]
+    [DataRow(typeof(Day13), "171", "539746751134958")]
+    [DataRow(typeof(Day14), "17481577045893", "4160009892257")]
+    [DataRow(typeof(Day15), "257", "8546398")]
+    [DataRow(typeof(Day16), "19093", "5311123569883")]
+    // [DataRow(typeof(Day17), "293", "1816")]
+    [DataRow(typeof(Day18), "12918250417632", "171259538712010")]
+    [DataRow(typeof(Day19), "160", "357")]
+    [DataRow(typeof(Day20), "21599955909991", "")]
+    [DataRow(typeof(Day21), "", "")]
+    [DataRow(typeof(Day22), "", "")]
+    [DataRow(typeof(Day23), "", "")]
+    [DataRow(typeof(Day24), "", "")]
+    [DataRow(typeof(Day25), "", "")]
+    public void CheckAllDays(Type dayType, string part1, string part2)
     {
-        [DataTestMethod]
+        // create day instance
-        [DataRow(typeof(Day01), "751776", "42275090")]
+        var s = Stopwatch.StartNew();
-        [DataRow(typeof(Day02), "556", "605")]
+        var day = Activator.CreateInstance(dayType) as Day;
-        [DataRow(typeof(Day03), "189", "1718180100")]
+        s.Stop();
-        [DataRow(typeof(Day04), "247", "145")]
+        Assert.IsNotNull(day, "failed to create day object");
-        [DataRow(typeof(Day05), "878", "504")]
+        Console.WriteLine($"{s.ScaleMilliseconds()}ms elapsed in constructor");
-        [DataRow(typeof(Day06), "6273", "3254")]
-        [DataRow(typeof(Day07), "169", "82372")]
-        [DataRow(typeof(Day08), "1654", "833")]
-        [DataRow(typeof(Day09), "138879426", "23761694")]
-        [DataRow(typeof(Day10), "1980", "4628074479616")]
-        [DataRow(typeof(Day11), "2303", "2057")]
-        [DataRow(typeof(Day12), "1710", "62045")]
-        [DataRow(typeof(Day13), "171", "539746751134958")]
-        [DataRow(typeof(Day14), "17481577045893", "4160009892257")]
-        [DataRow(typeof(Day15), "257", "8546398")]
-        [DataRow(typeof(Day16), "19093", "5311123569883")]
-        // [DataRow(typeof(Day17), "293", "1816")]
-        [DataRow(typeof(Day18), "12918250417632", "171259538712010")]
-        [DataRow(typeof(Day19), "160", "357")]
-        [DataRow(typeof(Day20), "21599955909991", "")]
-        [DataRow(typeof(Day21), "", "")]
-        [DataRow(typeof(Day22), "", "")]
-        [DataRow(typeof(Day23), "", "")]
-        [DataRow(typeof(Day24), "", "")]
-        [DataRow(typeof(Day25), "", "")]
-        public void CheckAllDays(Type dayType, string part1, string part2)
-        {
-            // create day instance
-            var s = Stopwatch.StartNew();
-            var day = (Day) Activator.CreateInstance(dayType);
-            s.Stop();
-            Assert.IsNotNull(day, "failed to create day object");
-            Console.WriteLine($"{s.ScaleMilliseconds()}ms elapsed in constructor");
 
-            // part 1
+        // part 1
-            s.Reset();
+        s.Reset();
-            s.Start();
+        s.Start();
-            var part1Actual = day.Part1();
+        var part1Actual = day.Part1();
-            s.Stop();
+        s.Stop();
-            Console.WriteLine($"{s.ScaleMilliseconds()}ms elapsed in part1");
+        Console.WriteLine($"{s.ScaleMilliseconds()}ms elapsed in part1");
-            Assert.AreEqual(part1, part1Actual, $"Incorrect answer for Day {day.DayNumber} Part1");
+        Assert.AreEqual(part1, part1Actual, $"Incorrect answer for Day {day.DayNumber} Part1");
 
-            // part 2
+        // part 2
-            s.Reset();
+        s.Reset();
-            s.Start();
+        s.Start();
-            var part2Actual = day.Part2();
+        var part2Actual = day.Part2();
-            s.Stop();
+        s.Stop();
-            Console.WriteLine($"{s.ScaleMilliseconds()}ms elapsed in part2");
+        Console.WriteLine($"{s.ScaleMilliseconds()}ms elapsed in part2");
-            Assert.AreEqual(part2, part2Actual, $"Incorrect answer for Day {day.DayNumber} Part2");
+        Assert.AreEqual(part2, part2Actual, $"Incorrect answer for Day {day.DayNumber} Part2");
-        }
     }
-}
+}

aoc2020.test/aoc2020.test.csproj

@@ -1,9 +1,10 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
-
+	<ImplicitUsings>enable</ImplicitUsings>
-    <IsPackable>false</IsPackable>
+	<Nullable>enable</Nullable>
+	<IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>

aoc2020/Day.cs

@@ -1,48 +1,44 @@
-using System;
-using System.Collections.Generic;
 using System.Diagnostics;
-using System.IO;
 
-namespace aoc2020
+namespace aoc2020;
+
+public abstract class Day
 {
-    public abstract class Day
+    protected Day(int dayNumber, string puzzleName)
     {
-        protected Day(int dayNumber, string puzzleName)
+        DayNumber = dayNumber;
-        {
+        PuzzleName = puzzleName;
-            DayNumber = dayNumber;
-            PuzzleName = puzzleName;
-        }
-
-        public int DayNumber { get; }
-        public string PuzzleName { get; }
-
-        protected IEnumerable<string> Input =>
-            File.ReadLines(FileName);
-
-        protected string FileName =>
-            Path.Combine(AppDomain.CurrentDomain.BaseDirectory, $"input/day{DayNumber,2:00}.in");
-
-        public abstract string Part1();
-        public abstract string Part2();
-
-        public void AllParts(bool verbose = true)
-        {
-            Console.WriteLine($"Day {DayNumber,2}: {PuzzleName}");
-            var s = Stopwatch.StartNew();
-            var part1 = Part1();
-            s.Stop();
-            Console.Write($"Part1: {part1,-15} ");
-            Console.WriteLine(verbose ? $"{s.ScaleMilliseconds()}ms elapsed" : "");
-
-            s.Reset();
-
-            s.Start();
-            var part2 = Part2();
-            s.Stop();
-            Console.Write($"Part2: {part2,-15} ");
-            Console.WriteLine(verbose ? $"{s.ScaleMilliseconds()}ms elapsed" : "");
-
-            Console.WriteLine();
-        }
     }
-}
+
+    public int DayNumber { get; }
+    public string PuzzleName { get; }
+
+    protected IEnumerable<string> Input =>
+        File.ReadLines(FileName);
+
+    protected string FileName =>
+        Path.Combine(AppDomain.CurrentDomain.BaseDirectory, $"input/day{DayNumber,2:00}.in");
+
+    public abstract string Part1();
+    public abstract string Part2();
+
+    public void AllParts(bool verbose = true)
+    {
+        Console.WriteLine($"Day {DayNumber,2}: {PuzzleName}");
+        var s = Stopwatch.StartNew();
+        var part1 = Part1();
+        s.Stop();
+        Console.Write($"Part1: {part1,-15} ");
+        Console.WriteLine(verbose ? $"{s.ScaleMilliseconds()}ms elapsed" : "");
+
+        s.Reset();
+
+        s.Start();
+        var part2 = Part2();
+        s.Stop();
+        Console.Write($"Part2: {part2,-15} ");
+        Console.WriteLine(verbose ? $"{s.ScaleMilliseconds()}ms elapsed" : "");
+
+        Console.WriteLine();
+    }
+}

aoc2020/Day01.cs

@@ -1,35 +1,31 @@
-using System.Collections.Immutable;
+namespace aoc2020;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 1: <see href="https://adventofcode.com/2020/day/1" />
+/// </summary>
+public sealed class Day01 : Day
 {
-    /// <summary>
+    private readonly ImmutableHashSet<int> _entries;
-    ///     Day 1: <see href="https://adventofcode.com/2020/day/1" />
+
-    /// </summary>
+    public Day01() : base(1, "Report Repair")
-    public sealed class Day01 : Day
     {
-        private readonly ImmutableHashSet<int> _entries;
+        _entries = Input.Select(int.Parse).ToImmutableHashSet();
-
-        public Day01() : base(1, "Report Repair")
-        {
-            _entries = Input.Select(int.Parse).ToImmutableHashSet();
-        }
-
-        public override string Part1()
-        {
-            var entry = _entries.First(e => _entries.Contains(2020 - e));
-            return $"{entry * (2020 - entry)}";
-        }
-
-        public override string Part2()
-        {
-            foreach (var i in _entries)
-            foreach (var j in _entries)
-            foreach (var k in _entries)
-                if (i + j + k == 2020)
-                    return $"{i * j * k}";
-
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        var entry = _entries.First(e => _entries.Contains(2020 - e));
+        return $"{entry * (2020 - entry)}";
+    }
+
+    public override string Part2()
+    {
+        foreach (var i in _entries)
+            foreach (var j in _entries)
+                foreach (var k in _entries)
+                    if (i + j + k == 2020)
+                        return $"{i * j * k}";
+
+        return "";
+    }
+}

aoc2020/Day02.cs

@@ -1,56 +1,52 @@
-using System.Collections.Immutable;
+namespace aoc2020;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 2: <see href="https://adventofcode.com/2020/day/1" />
+/// </summary>
+public sealed class Day02 : Day
 {
-    /// <summary>
+    private readonly ImmutableList<Password> _passwords;
-    ///     Day 2: <see href="https://adventofcode.com/2020/day/1" />
+
-    /// </summary>
+    public Day02() : base(2, "Password Philosophy")
-    public sealed class Day02 : Day
     {
-        private readonly ImmutableList<Password> _passwords;
+        _passwords = Input.Select(p => new Password(p)).ToImmutableList();
-
-        public Day02() : base(2, "Password Philosophy")
-        {
-            _passwords = Input.Select(p => new Password(p)).ToImmutableList();
-        }
-
-        public override string Part1()
-        {
-            return $"{_passwords.Count(p => p.IsValid)}";
-        }
-
-        public override string Part2()
-        {
-            return $"{_passwords.Count(p => p.IsValidByIndex)}";
-        }
-
-        private class Password
-        {
-            public Password(string line)
-            {
-                var split = line.Split(": ", 2);
-                var split2 = split[0].Split(' ', 2);
-                var indices = split2[0].Split('-', 2);
-                I = int.Parse(indices[0]);
-                J = int.Parse(indices[1]);
-                C = char.Parse(split2[1]);
-                Value = split[1];
-            }
-
-            public bool IsValid =>
-                Count >= I && Count <= J;
-
-            public bool IsValidByIndex =>
-                (Value[I - 1] == C) ^ (Value[J - 1] == C);
-
-            private int Count =>
-                Value.Count(p => p == C);
-
-            private int I { get; }
-            private int J { get; }
-            private char C { get; }
-            private string Value { get; }
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return $"{_passwords.Count(p => p.IsValid)}";
+    }
+
+    public override string Part2()
+    {
+        return $"{_passwords.Count(p => p.IsValidByIndex)}";
+    }
+
+    private class Password
+    {
+        public Password(string line)
+        {
+            var split = line.Split(": ", 2);
+            var split2 = split[0].Split(' ', 2);
+            var indices = split2[0].Split('-', 2);
+            I = int.Parse(indices[0]);
+            J = int.Parse(indices[1]);
+            C = char.Parse(split2[1]);
+            Value = split[1];
+        }
+
+        public bool IsValid =>
+            Count >= I && Count <= J;
+
+        public bool IsValidByIndex =>
+            (Value[I - 1] == C) ^ (Value[J - 1] == C);
+
+        private int Count =>
+            Value.Count(p => p == C);
+
+        private int I { get; }
+        private int J { get; }
+        private char C { get; }
+        private string Value { get; }
+    }
+}

aoc2020/Day03.cs

@@ -1,45 +1,42 @@
-using System.Linq;
+namespace aoc2020;
 
-namespace aoc2020
+/// <summary>
+///     Day 3: <see href="https://adventofcode.com/2020/day/3" />
+/// </summary>
+public sealed class Day03 : Day
 {
-    /// <summary>
+    private readonly string[] _grid;
-    ///     Day 3: <see href="https://adventofcode.com/2020/day/3" />
+    private readonly int _width;
-    /// </summary>
+
-    public sealed class Day03 : Day
+    public Day03() : base(3, "Toboggan Trajectory")
     {
-        private readonly string[] _grid;
+        _grid = Input.ToArray();
-        private readonly int _width;
+        _width = _grid[0].Length;
-
-        public Day03() : base(3, "Toboggan Trajectory")
-        {
-            _grid = Input.ToArray();
-            _width = _grid[0].Length;
-        }
-
-        private long CountSlope(int dx, int dy)
-        {
-            long hits = 0;
-            for (int x = 0, y = 0; y < _grid.Length; y += dy, x = (x + dx) % _width)
-                if (_grid[y][x] == '#')
-                    hits++;
-
-            return hits;
-        }
-
-        public override string Part1()
-        {
-            return $"{CountSlope(3, 1)}";
-        }
-
-        public override string Part2()
-        {
-            var xSlopes = new[] {1, 3, 5, 7, 1};
-            var ySlopes = new[] {1, 1, 1, 1, 2};
-
-            return xSlopes.Zip(ySlopes)
-                .Select(s => CountSlope(s.Item1, s.Item2))
-                .Aggregate((acc, i) => acc * i)
-                .ToString();
-        }
     }
-}
+
+    private long CountSlope(int dx, int dy)
+    {
+        long hits = 0;
+        for (int x = 0, y = 0; y < _grid.Length; y += dy, x = (x + dx) % _width)
+            if (_grid[y][x] == '#')
+                hits++;
+
+        return hits;
+    }
+
+    public override string Part1()
+    {
+        return $"{CountSlope(3, 1)}";
+    }
+
+    public override string Part2()
+    {
+        var xSlopes = new[] { 1, 3, 5, 7, 1 };
+        var ySlopes = new[] { 1, 1, 1, 1, 2 };
+
+        return xSlopes.Zip(ySlopes)
+            .Select(s => CountSlope(s.First, s.Second))
+            .Aggregate((acc, i) => acc * i)
+            .ToString();
+    }
+}

aoc2020/Day04.cs

@@ -1,188 +1,182 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text.RegularExpressions;
 
-namespace aoc2020
+/// <summary>
+///     Day 4: <see href="https://adventofcode.com/2020/day/4" />
+/// </summary>
+public sealed class Day04 : Day
 {
-    /// <summary>
+    private readonly List<Passport> _passports;
-    ///     Day 4: <see href="https://adventofcode.com/2020/day/4" />
+
-    /// </summary>
+    public Day04() : base(4, "Passport Processing")
-    public sealed class Day04 : Day
     {
-        private readonly List<Passport> _passports;
+        _passports = new List<Passport>();
 
-        public Day04() : base(4, "Passport Processing")
+        var a = new List<string>();
+        foreach (var line in Input)
         {
-            _passports = new List<Passport>();
+            if (line == "")
-
-            var a = new List<string>();
-            foreach (var line in Input)
             {
-                if (line == "")
+                _passports.Add(Passport.Parse(a));
-                {
+                a.Clear();
-                    _passports.Add(Passport.Parse(a));
+                continue;
-                    a.Clear();
-                    continue;
-                }
-
-                a.Add(line);
             }
 
-            if (a.Any()) _passports.Add(Passport.Parse(a));
+            a.Add(line);
         }
 
-        public override string Part1()
+        if (a.Any()) _passports.Add(Passport.Parse(a));
+    }
+
+    public override string Part1()
+    {
+        return $"{_passports.Count(p => p.IsValid)}";
+    }
+
+    public override string Part2()
+    {
+        return $"{_passports.Count(p => p.ExtendedValidation())}";
+    }
+
+    private class Passport
+    {
+        private string _byr;
+        private string _cid;
+        private string _ecl;
+        private string _eyr;
+        private string _hcl;
+        private string _hgt;
+        private string _iyr;
+        private string _pid;
+
+        public bool IsValid =>
+            _byr != null &&
+            _iyr != null &&
+            _eyr != null &&
+            _hgt != null &&
+            _hcl != null &&
+            _ecl != null &&
+            _pid != null;
+
+        public bool ExtendedValidation()
         {
-            return $"{_passports.Count(p => p.IsValid)}";
+            if (!IsValid) return false;
-        }
 
-        public override string Part2()
+            // birth year
-        {
+            if (int.TryParse(_byr, out var byr))
-            return $"{_passports.Count(p => p.ExtendedValidation())}";
-        }
-
-        private class Passport
-        {
-            private string _byr;
-            private string _cid;
-            private string _ecl;
-            private string _eyr;
-            private string _hcl;
-            private string _hgt;
-            private string _iyr;
-            private string _pid;
-
-            public bool IsValid =>
-                _byr != null &&
-                _iyr != null &&
-                _eyr != null &&
-                _hgt != null &&
-                _hcl != null &&
-                _ecl != null &&
-                _pid != null;
-
-            public bool ExtendedValidation()
             {
-                if (!IsValid) return false;
+                if (byr < 1920 || byr > 2002)
-
-                // birth year
-                if (int.TryParse(_byr, out var byr))
-                {
-                    if (byr < 1920 || byr > 2002)
-                        return false;
-                }
-                else
-                {
                     return false;
-                }
+            }
-
+            else
-                // issuance year
+            {
-                if (int.TryParse(_iyr, out var iyr))
+                return false;
-                {
-                    if (iyr < 2010 || iyr > 2020)
-                        return false;
-                }
-                else
-                {
-                    return false;
-                }
-
-                // expiration year
-                if (int.TryParse(_eyr, out var eyr))
-                {
-                    if (eyr < 2020 || eyr > 2030)
-                        return false;
-                }
-                else
-                {
-                    return false;
-                }
-
-                // height
-                if (_hgt.EndsWith("cm"))
-                {
-                    var h = _hgt.Substring(0, 3);
-                    if (int.TryParse(h, out var hgt))
-                    {
-                        if (hgt < 150 || hgt > 193)
-                            return false;
-                    }
-                    else
-                    {
-                        return false;
-                    }
-                }
-                else if (_hgt.EndsWith("in"))
-                {
-                    var h = _hgt.Substring(0, 2);
-                    if (int.TryParse(h, out var hgt))
-                    {
-                        if (hgt < 59 || hgt > 76)
-                            return false;
-                    }
-                    else
-                    {
-                        return false;
-                    }
-                }
-                else
-                {
-                    return false;
-                }
-
-                // hair color
-                if (!Regex.IsMatch(_hcl, "#[0-9a-f]{6}"))
-                    return false;
-
-                // eye color
-                if (!new[] {"amb", "blu", "brn", "gry", "grn", "hzl", "oth"}.Contains(_ecl))
-                    return false;
-
-                // passport id
-                if (_pid.Length != 9)
-                    return false;
-
-                return true;
             }
 
-            public static Passport Parse(IEnumerable<string> list)
+            // issuance year
+            if (int.TryParse(_iyr, out var iyr))
             {
-                var passport = new Passport();
+                if (iyr < 2010 || iyr > 2020)
-                foreach (var entry in string.Join(' ', list).Split(' ', StringSplitOptions.TrimEntries))
+                    return false;
-                {
-                    var spl = entry.Split(':', 2);
-                    switch (spl[0])
-                    {
-                        case "byr":
-                            passport._byr = spl[1];
-                            break;
-                        case "iyr":
-                            passport._iyr = spl[1];
-                            break;
-                        case "eyr":
-                            passport._eyr = spl[1];
-                            break;
-                        case "hgt":
-                            passport._hgt = spl[1];
-                            break;
-                        case "hcl":
-                            passport._hcl = spl[1];
-                            break;
-                        case "ecl":
-                            passport._ecl = spl[1];
-                            break;
-                        case "pid":
-                            passport._pid = spl[1];
-                            break;
-                        case "cid":
-                            passport._cid = spl[1];
-                            break;
-                    }
-                }
-
-                return passport;
             }
+            else
+            {
+                return false;
+            }
+
+            // expiration year
+            if (int.TryParse(_eyr, out var eyr))
+            {
+                if (eyr < 2020 || eyr > 2030)
+                    return false;
+            }
+            else
+            {
+                return false;
+            }
+
+            // height
+            if (_hgt.EndsWith("cm"))
+            {
+                var h = _hgt[..3];
+                if (int.TryParse(h, out var hgt))
+                {
+                    if (hgt < 150 || hgt > 193)
+                        return false;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+            else if (_hgt.EndsWith("in"))
+            {
+                var h = _hgt.Substring(0, 2);
+                if (int.TryParse(h, out var hgt))
+                {
+                    if (hgt < 59 || hgt > 76)
+                        return false;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                return false;
+            }
+
+            // hair color
+            if (!Regex.IsMatch(_hcl, "#[0-9a-f]{6}"))
+                return false;
+
+            // eye color
+            if (!new[] { "amb", "blu", "brn", "gry", "grn", "hzl", "oth" }.Contains(_ecl))
+                return false;
+
+            // passport id
+            if (_pid.Length != 9)
+                return false;
+
+            return true;
+        }
+
+        public static Passport Parse(IEnumerable<string> list)
+        {
+            var passport = new Passport();
+            foreach (var entry in string.Join(' ', list).Split(' ', StringSplitOptions.TrimEntries))
+            {
+                var spl = entry.Split(':', 2);
+                switch (spl[0])
+                {
+                    case "byr":
+                        passport._byr = spl[1];
+                        break;
+                    case "iyr":
+                        passport._iyr = spl[1];
+                        break;
+                    case "eyr":
+                        passport._eyr = spl[1];
+                        break;
+                    case "hgt":
+                        passport._hgt = spl[1];
+                        break;
+                    case "hcl":
+                        passport._hcl = spl[1];
+                        break;
+                    case "ecl":
+                        passport._ecl = spl[1];
+                        break;
+                    case "pid":
+                        passport._pid = spl[1];
+                        break;
+                    case "cid":
+                        passport._cid = spl[1];
+                        break;
+                }
+            }
+
+            return passport;
         }
     }
-}
+}

aoc2020/Day05.cs

@@ -1,34 +1,29 @@
-using System;
+namespace aoc2020;
-using System.Collections.Immutable;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 5: <see href="https://adventofcode.com/2020/day/5" />
+/// </summary>
+public sealed class Day05 : Day
 {
-    /// <summary>
+    private readonly ImmutableHashSet<int> _ids;
-    ///     Day 5: <see href="https://adventofcode.com/2020/day/5" />
+
-    /// </summary>
+    public Day05() : base(5, "Binary Boarding")
-    public sealed class Day05 : Day
     {
-        private readonly ImmutableHashSet<int> _ids;
+        _ids = Input
-
+            .Select(s =>
-        public Day05() : base(5, "Binary Boarding")
+                Convert.ToInt32(s.Replace('F', '0').Replace('B', '1').Replace('L', '0').Replace('R', '1'), 2))
-        {
+            .OrderBy(i => i)
-            _ids = Input
+            .ToImmutableHashSet();
-                .Select(s =>
-                    Convert.ToInt32(s.Replace('F', '0').Replace('B', '1').Replace('L', '0').Replace('R', '1'), 2))
-                .OrderBy(i => i)
-                .ToImmutableHashSet();
-        }
-
-        public override string Part1()
-        {
-            return $"{_ids.Last()}";
-        }
-
-        public override string Part2()
-        {
-            // arithmetic sum of full series
-            return $"{(_ids.Count + 1) * (_ids.First() + _ids.Last()) / 2 - _ids.Sum()}";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return $"{_ids.Last()}";
+    }
+
+    public override string Part2()
+    {
+        // arithmetic sum of full series
+        return $"{(_ids.Count + 1) * (_ids.First() + _ids.Last()) / 2 - _ids.Sum()}";
+    }
+}

aoc2020/Day06.cs

@@ -1,54 +1,50 @@
-using System.Collections.Generic;
+namespace aoc2020;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 6: <see href="https://adventofcode.com/2020/day/6" />
+/// </summary>
+public sealed class Day06 : Day
 {
-    /// <summary>
+    private readonly int _countPart1;
-    ///     Day 6: <see href="https://adventofcode.com/2020/day/6" />
+    private readonly int _countPart2;
-    /// </summary>
+
-    public sealed class Day06 : Day
+    public Day06() : base(6, "Custom Customs")
     {
-        private readonly int _countPart1;
+        var alphabet = "abcedfghijklmnopqrstuvwxyz".ToCharArray();
-        private readonly int _countPart2;
+        _countPart1 = 0;
-
+        _countPart2 = 0;
-        public Day06() : base(6, "Custom Customs")
+        var s = new HashSet<char>();
+        var lines = new HashSet<string>();
+        foreach (var line in Input)
         {
-            var alphabet = "abcedfghijklmnopqrstuvwxyz".ToCharArray();
+            if (line == "")
-            _countPart1 = 0;
-            _countPart2 = 0;
-            var s = new HashSet<char>();
-            var lines = new HashSet<string>();
-            foreach (var line in Input)
-            {
-                if (line == "")
-                {
-                    _countPart1 += s.Count;
-                    _countPart2 += alphabet.Count(a => lines.All(l => l.Contains(a)));
-                    s.Clear();
-                    lines.Clear();
-                    continue;
-                }
-
-                foreach (var c in line)
-                    s.Add(c);
-                lines.Add(line);
-            }
-
-            if (s.Any())
             {
                 _countPart1 += s.Count;
                 _countPart2 += alphabet.Count(a => lines.All(l => l.Contains(a)));
+                s.Clear();
+                lines.Clear();
+                continue;
             }
+
+            foreach (var c in line)
+                s.Add(c);
+            lines.Add(line);
         }
 
-        public override string Part1()
+        if (s.Any())
         {
-            return $"{_countPart1}";
+            _countPart1 += s.Count;
-        }
+            _countPart2 += alphabet.Count(a => lines.All(l => l.Contains(a)));
-
-        public override string Part2()
-        {
-            return $"{_countPart2}";
         }
     }
-}
+
+    public override string Part1()
+    {
+        return $"{_countPart1}";
+    }
+
+    public override string Part2()
+    {
+        return $"{_countPart2}";
+    }
+}

aoc2020/Day07.cs

@@ -1,61 +1,57 @@
-using System.Collections.Generic;
+namespace aoc2020;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 7: <see href="https://adventofcode.com/2020/day/7" />
+/// </summary>
+public sealed class Day07 : Day
 {
-    /// <summary>
+    private readonly Dictionary<string, IEnumerable<(int, string)?>> _rules;
-    ///     Day 7: <see href="https://adventofcode.com/2020/day/7" />
+
-    /// </summary>
+    public Day07() : base(7, "Handy Haversacks")
-    public sealed class Day07 : Day
     {
-        private readonly Dictionary<string, IEnumerable<(int, string)?>> _rules;
+        _rules = Input.Select(rule =>
-
-        public Day07() : base(7, "Handy Haversacks")
-        {
-            _rules = Input.Select(rule =>
-                {
-                    var spl = rule.Split(" bags contain ", 2);
-                    var outer = string.Join(' ', spl[0].Split(' ').Take(2));
-                    var inner = spl[1].Split(", ").Select(ParseQuantity).Where(i => i != null);
-                    return (outer, inner);
-                })
-                .ToDictionary(t => t.outer, t => t.inner);
-        }
-
-        private static (int, string)? ParseQuantity(string arg)
-        {
-            if (arg == "no other bags.") return null;
-            var words = arg.Split(' ');
-            return (int.Parse(words[0]), string.Join(' ', words[1..3]));
-        }
-
-        private int Weight(string node)
-        {
-            return 1 + _rules[node].Sum(i => i.Value.Item1 * Weight(i.Value.Item2));
-        }
-
-        public override string Part1()
-        {
-            // breadth-first search with Queue
-            var start = new Queue<string>(new[] {"shiny gold"});
-            var p = new HashSet<string>();
-            string node;
-            while (true)
             {
-                node = start.Dequeue();
+                var spl = rule.Split(" bags contain ", 2);
-                foreach (var (container, contained) in _rules)
+                var outer = string.Join(' ', spl[0].Split(' ').Take(2));
-                    if (contained.Any(i => i.HasValue && i.Value.Item2 == node) && p.Add(container))
+                var inner = spl[1].Split(", ").Select(ParseQuantity).Where(i => i != null);
-                        start.Enqueue(container);
+                return (outer, inner);
-
+            })
-                if (!start.Any()) break;
+            .ToDictionary(t => t.outer, t => t.inner);
-            }
-
-            return $"{p.Count}";
-        }
-
-        public override string Part2()
-        {
-            return $"{Weight("shiny gold") - 1}";
-        }
     }
-}
+
+    private static (int, string)? ParseQuantity(string arg)
+    {
+        if (arg == "no other bags.") return null;
+        var words = arg.Split(' ');
+        return (int.Parse(words[0]), string.Join(' ', words[1..3]));
+    }
+
+    private int Weight(string node)
+    {
+        return 1 + _rules[node].Sum(i => i.Value.Item1 * Weight(i.Value.Item2));
+    }
+
+    public override string Part1()
+    {
+        // breadth-first search with Queue
+        var start = new Queue<string>(new[] { "shiny gold" });
+        var p = new HashSet<string>();
+        string node;
+        while (true)
+        {
+            node = start.Dequeue();
+            foreach (var (container, contained) in _rules)
+                if (contained.Any(i => i.HasValue && i.Value.Item2 == node) && p.Add(container))
+                    start.Enqueue(container);
+
+            if (!start.Any()) break;
+        }
+
+        return $"{p.Count}";
+    }
+
+    public override string Part2()
+    {
+        return $"{Weight("shiny gold") - 1}";
+    }
+}

aoc2020/Day08.cs

@@ -1,77 +1,74 @@
-using System.Linq;
+namespace aoc2020;
 
-namespace aoc2020
+/// <summary>
+///     Day 8: <see href="https://adventofcode.com/2020/day/8" />
+/// </summary>
+public sealed class Day08 : Day
 {
-    /// <summary>
+    private readonly (string instruction, int value)[] _instructions;
-    ///     Day 8: <see href="https://adventofcode.com/2020/day/8" />
+    private int _accumulator;
-    /// </summary>
+    private int _currentInstruction;
-    public sealed class Day08 : Day
+
+    public Day08() : base(8, "Handheld Halting")
     {
-        private readonly (string instruction, int value)[] _instructions;
+        _instructions = Input.Select(ParseLine).ToArray();
-        private int _accumulator;
+    }
-        private int _currentInstruction;
 
-        public Day08() : base(8, "Handheld Halting")
+    private static (string, int) ParseLine(string line)
+    {
+        var spl = line.Split(' ', 2);
+        return (spl[0], int.Parse(spl[1]));
+    }
+
+    private bool Halts()
+    {
+        _accumulator = 0;
+        _currentInstruction = 0;
+        var visited = new bool[_instructions.Length + 1];
+
+        while (!visited[_currentInstruction] && _currentInstruction < _instructions.Length)
         {
-            _instructions = Input.Select(ParseLine).ToArray();
+            visited[_currentInstruction] = true;
-        }
 
-        private static (string, int) ParseLine(string line)
+            switch (_instructions[_currentInstruction].instruction)
-        {
-            var spl = line.Split(' ', 2);
-            return (spl[0], int.Parse(spl[1]));
-        }
-
-        private bool Halts()
-        {
-            _accumulator = 0;
-            _currentInstruction = 0;
-            var visited = new bool[_instructions.Length + 1];
-
-            while (!visited[_currentInstruction] && _currentInstruction < _instructions.Length)
             {
-                visited[_currentInstruction] = true;
+                case "acc":
-
+                    _accumulator += _instructions[_currentInstruction].value;
-                switch (_instructions[_currentInstruction].instruction)
+                    break;
-                {
+                case "jmp":
-                    case "acc":
+                    _currentInstruction += _instructions[_currentInstruction].value;
-                        _accumulator += _instructions[_currentInstruction].value;
+                    continue;
-                        break;
-                    case "jmp":
-                        _currentInstruction += _instructions[_currentInstruction].value;
-                        continue;
-                }
-
-                _currentInstruction++;
             }
 
-            return _currentInstruction == _instructions.Length;
+            _currentInstruction++;
         }
 
-        public override string Part1()
+        return _currentInstruction == _instructions.Length;
-        {
-            Halts();
-            return $"{_accumulator}";
-        }
-
-        public override string Part2()
-        {
-            for (var i = 0; i < _instructions.Length; i++)
-                // swap each nop and jmp and check if the program halts
-                if (_instructions[i].instruction == "nop")
-                {
-                    _instructions[i].instruction = "jmp";
-                    if (Halts()) break;
-                    _instructions[i].instruction = "nop";
-                }
-                else if (_instructions[i].instruction == "jmp")
-                {
-                    _instructions[i].instruction = "nop";
-                    if (Halts()) break;
-                    _instructions[i].instruction = "jmp";
-                }
-
-            return $"{_accumulator}";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        Halts();
+        return $"{_accumulator}";
+    }
+
+    public override string Part2()
+    {
+        for (var i = 0; i < _instructions.Length; i++)
+            // swap each nop and jmp and check if the program halts
+            if (_instructions[i].instruction == "nop")
+            {
+                _instructions[i].instruction = "jmp";
+                if (Halts()) break;
+                _instructions[i].instruction = "nop";
+            }
+            else if (_instructions[i].instruction == "jmp")
+            {
+                _instructions[i].instruction = "nop";
+                if (Halts()) break;
+                _instructions[i].instruction = "jmp";
+            }
+
+        return $"{_accumulator}";
+    }
+}

aoc2020/Day09.cs

@@ -1,52 +1,49 @@
-using System.Linq;
+namespace aoc2020;
 
-namespace aoc2020
+/// <summary>
+///     Day 9: <see href="https://adventofcode.com/2020/day/9" />
+/// </summary>
+public sealed class Day09 : Day
 {
-    /// <summary>
+    private readonly long[] _list;
-    ///     Day 9: <see href="https://adventofcode.com/2020/day/9" />
+    private long _part1;
-    /// </summary>
+
-    public sealed class Day09 : Day
+    public Day09() : base(9, "Encoding Error")
     {
-        private readonly long[] _list;
+        _list = Input.Select(long.Parse).ToArray();
-        private long _part1;
-
-        public Day09() : base(9, "Encoding Error")
-        {
-            _list = Input.Select(long.Parse).ToArray();
-        }
-
-        public override string Part1()
-        {
-            for (var i = 25; i < _list.Length - 25; i++)
-            {
-                var preamble = _list[(i - 25)..i];
-                if (!preamble.Any(num1 => preamble.Any(num2 => num1 + num2 == _list[i])))
-                {
-                    _part1 = _list[i];
-                    return $"{_part1}";
-                }
-            }
-
-            return "";
-        }
-
-        public override string Part2()
-        {
-            for (var i = 0; i < _list.Length; i++)
-            {
-                long sum = 0;
-                for (var j = i; j < _list.Length; j++)
-                {
-                    sum += _list[j];
-                    if (sum > _part1) break;
-                    if (sum != _part1) continue;
-
-                    var subset = _list[i..(j + 1)].ToArray();
-                    return $"{subset.Min() + subset.Max()}";
-                }
-            }
-
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        for (var i = 25; i < _list.Length - 25; i++)
+        {
+            var preamble = _list[(i - 25)..i];
+            if (!preamble.Any(num1 => preamble.Any(num2 => num1 + num2 == _list[i])))
+            {
+                _part1 = _list[i];
+                return $"{_part1}";
+            }
+        }
+
+        return "";
+    }
+
+    public override string Part2()
+    {
+        for (var i = 0; i < _list.Length; i++)
+        {
+            long sum = 0;
+            for (var j = i; j < _list.Length; j++)
+            {
+                sum += _list[j];
+                if (sum > _part1) break;
+                if (sum != _part1) continue;
+
+                var subset = _list[i..(j + 1)].ToArray();
+                return $"{subset.Min() + subset.Max()}";
+            }
+        }
+
+        return "";
+    }
+}

aoc2020/Day10.cs

@@ -1,59 +1,55 @@
-using System;
+namespace aoc2020;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 10: <see href="https://adventofcode.com/2020/day/10" />
+/// </summary>
+public sealed class Day10 : Day
 {
-    /// <summary>
+    private readonly int[] _adapters;
-    ///     Day 10: <see href="https://adventofcode.com/2020/day/10" />
+    private readonly long[] _memo;
-    /// </summary>
+
-    public sealed class Day10 : Day
+    public Day10() : base(10, "Adapter Array")
     {
-        private readonly int[] _adapters;
+        var parsed = Input.Select(int.Parse).ToArray();
-        private readonly long[] _memo;
+        // add socket and device to the list
-
+        _adapters = parsed.Concat(new[] { 0, parsed.Max() + 3 }).OrderBy(i => i).ToArray();
-        public Day10() : base(10, "Adapter Array")
+        _memo = new long[_adapters.Length];
-        {
-            var parsed = Input.Select(int.Parse).ToArray();
-            // add socket and device to the list
-            _adapters = parsed.Concat(new[] {0, parsed.Max() + 3}).OrderBy(i => i).ToArray();
-            _memo = new long[_adapters.Length];
-        }
-
-        private long Connections(int i)
-        {
-            if (i == _adapters.Length - 1) _memo[i] = 1;
-            if (_memo[i] > 0) return _memo[i];
-
-            for (var j = i + 1; j <= i + 3 && j < _adapters.Length; j++)
-                if (_adapters[j] - _adapters[i] <= 3)
-                    _memo[i] += Connections(j);
-
-            return _memo[i];
-        }
-
-        public override string Part1()
-        {
-            var ones = 0;
-            var threes = 0;
-
-            for (var i = 0; i < _adapters.Length - 1; i++)
-                switch (_adapters[i + 1] - _adapters[i])
-                {
-                    case 1:
-                        ones++;
-                        break;
-                    case 3:
-                        threes++;
-                        break;
-                    default: throw new Exception("something went wrong");
-                }
-
-            return $"{ones * threes}";
-        }
-
-        public override string Part2()
-        {
-            return $"{Connections(0)}";
-        }
     }
-}
+
+    private long Connections(int i)
+    {
+        if (i == _adapters.Length - 1) _memo[i] = 1;
+        if (_memo[i] > 0) return _memo[i];
+
+        for (var j = i + 1; j <= i + 3 && j < _adapters.Length; j++)
+            if (_adapters[j] - _adapters[i] <= 3)
+                _memo[i] += Connections(j);
+
+        return _memo[i];
+    }
+
+    public override string Part1()
+    {
+        var ones = 0;
+        var threes = 0;
+
+        for (var i = 0; i < _adapters.Length - 1; i++)
+            switch (_adapters[i + 1] - _adapters[i])
+            {
+                case 1:
+                    ones++;
+                    break;
+                case 3:
+                    threes++;
+                    break;
+                default: throw new Exception("something went wrong");
+            }
+
+        return $"{ones * threes}";
+    }
+
+    public override string Part2()
+    {
+        return $"{Connections(0)}";
+    }
+}

aoc2020/Day11.cs

@@ -1,91 +1,87 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 11: <see href="https://adventofcode.com/2020/day/11" />
+/// </summary>
+public sealed class Day11 : Day
 {
-    /// <summary>
+    public Day11() : base(11, "Seating System")
-    ///     Day 11: <see href="https://adventofcode.com/2020/day/11" />
-    /// </summary>
-    public sealed class Day11 : Day
     {
-        public Day11() : base(11, "Seating System")
+    }
+
+    public override string Part1()
+    {
+        var prev = new LifeGame(Input);
+
+        while (true)
+        {
+            var next = prev.StepPart1();
+            var same = true;
+            for (var i = 0; i < next.Grid.Length; i++)
+                if (!next.Grid[i].SequenceEqual(prev.Grid[i]))
+                {
+                    same = false;
+                    break;
+                }
+
+            if (same) break;
+            prev = next;
+        }
+
+        return $"{prev.TotalSeated}";
+    }
+
+    public override string Part2()
+    {
+        var prev = new LifeGame(Input);
+        while (true)
+        {
+            var next = prev.StepPart2();
+            var same = true;
+            for (var i = 0; i < next.Grid.Length; i++)
+                if (!next.Grid[i].SequenceEqual(prev.Grid[i]))
+                {
+                    same = false;
+                    break;
+                }
+
+            if (same) break;
+            prev = next;
+        }
+
+        return $"{prev.TotalSeated}";
+    }
+
+    private class LifeGame
+    {
+        private int _h, _w;
+        public char[][] Grid;
+
+        public LifeGame(IEnumerable<string> input)
+        {
+            Grid = input.Select(line => line.ToCharArray()).ToArray();
+            _h = Grid.Length;
+            _w = Grid[0].Length;
+        }
+
+        private LifeGame()
         {
         }
 
-        public override string Part1()
+        public int TotalSeated =>
+            Grid.Sum(l => l.Count(c => c == '#'));
+
+        private void PrintBoard()
         {
-            var prev = new LifeGame(Input);
+            Console.Clear();
-
+            foreach (var line in Grid)
-            while (true)
+                Console.WriteLine(line);
-            {
-                var next = prev.StepPart1();
-                var same = true;
-                for (var i = 0; i < next.Grid.Length; i++)
-                    if (!next.Grid[i].SequenceEqual(prev.Grid[i]))
-                    {
-                        same = false;
-                        break;
-                    }
-
-                if (same) break;
-                prev = next;
-            }
-
-            return $"{prev.TotalSeated}";
         }
 
-        public override string Part2()
+        public LifeGame StepPart1()
         {
-            var prev = new LifeGame(Input);
+            var next = new LifeGame { _h = _h, _w = _w, Grid = Grid.Select(s => s.ToArray()).ToArray() };
-            while (true)
+            for (var y = 0; y < _h; y++)
-            {
-                var next = prev.StepPart2();
-                var same = true;
-                for (var i = 0; i < next.Grid.Length; i++)
-                    if (!next.Grid[i].SequenceEqual(prev.Grid[i]))
-                    {
-                        same = false;
-                        break;
-                    }
-
-                if (same) break;
-                prev = next;
-            }
-
-            return $"{prev.TotalSeated}";
-        }
-
-        private class LifeGame
-        {
-            private int _h, _w;
-            public char[][] Grid;
-
-            public LifeGame(IEnumerable<string> input)
-            {
-                Grid = input.Select(line => line.ToCharArray()).ToArray();
-                _h = Grid.Length;
-                _w = Grid[0].Length;
-            }
-
-            private LifeGame()
-            {
-            }
-
-            public int TotalSeated =>
-                Grid.Sum(l => l.Count(c => c == '#'));
-
-            private void PrintBoard()
-            {
-                Console.Clear();
-                foreach (var line in Grid)
-                    Console.WriteLine(line);
-            }
-
-            public LifeGame StepPart1()
-            {
-                var next = new LifeGame {_h = _h, _w = _w, Grid = Grid.Select(s => s.ToArray()).ToArray()};
-                for (var y = 0; y < _h; y++)
                 for (var x = 0; x < _w; x++)
                     next.Grid[y][x] = Grid[y][x] switch
                     {
@@ -94,29 +90,29 @@ namespace aoc2020
                         _ => Grid[y][x]
                     };
 
-                // next.PrintBoard();
+            // next.PrintBoard();
-                return next;
+            return next;
-            }
+        }
 
-            private char At(int y, int x)
+        private char At(int y, int x)
-            {
+        {
-                return x < 0 || y < 0 || x >= _w || y >= _h ? '.' : Grid[y][x];
+            return x < 0 || y < 0 || x >= _w || y >= _h ? '.' : Grid[y][x];
-            }
+        }
 
-            private int CountAdjacent(int y, int x)
+        private int CountAdjacent(int y, int x)
+        {
+            return new[]
             {
-                return new[]
-                {
                     At(y - 1, x - 1), At(y - 1, x + 0), At(y - 1, x + 1),
                     At(y + 0, x - 1), At(y + 0, x + 1),
                     At(y + 1, x - 1), At(y + 1, x + 0), At(y + 1, x + 1)
                 }.Count(c => c == '#');
-            }
+        }
 
-            public LifeGame StepPart2()
+        public LifeGame StepPart2()
-            {
+        {
-                var next = new LifeGame {_h = _h, _w = _w, Grid = Grid.Select(s => s.ToArray()).ToArray()};
+            var next = new LifeGame { _h = _h, _w = _w, Grid = Grid.Select(s => s.ToArray()).ToArray() };
-                for (var y = 0; y < _h; y++)
+            for (var y = 0; y < _h; y++)
                 for (var x = 0; x < _w; x++)
                     next.Grid[y][x] = Grid[y][x] switch
                     {
@@ -125,33 +121,32 @@ namespace aoc2020
                         _ => Grid[y][x]
                     };
 
-                // next.PrintBoard();
+            // next.PrintBoard();
-                return next;
+            return next;
-            }
+        }
 
-            private int CanSee(int y, int x)
+        private int CanSee(int y, int x)
+        {
+            return new[]
             {
-                return new[]
-                {
                     TraceRay(y, x, -1, -1), TraceRay(y, x, -1, +0), TraceRay(y, x, -1, +1),
                     TraceRay(y, x, +0, -1), TraceRay(y, x, +0, +1),
                     TraceRay(y, x, +1, -1), TraceRay(y, x, +1, +0), TraceRay(y, x, +1, +1)
                 }.Count(c => c == '#');
-            }
+        }
 
-            private char TraceRay(int y, int x, int dy, int dx)
+        private char TraceRay(int y, int x, int dy, int dx)
+        {
+            y += dy;
+            x += dx;
+            while (y >= 0 && y < _h && x >= 0 && x < _w)
             {
+                if (Grid[y][x] != '.') return Grid[y][x];
                 y += dy;
                 x += dx;
-                while (y >= 0 && y < _h && x >= 0 && x < _w)
-                {
-                    if (Grid[y][x] != '.') return Grid[y][x];
-                    y += dy;
-                    x += dx;
-                }
-
-                return '.';
             }
+
+            return '.';
         }
     }
-}
+}

aoc2020/Day12.cs

@@ -1,94 +1,89 @@
-using System;
+namespace aoc2020;
 
-namespace aoc2020
+/// <summary>
+///     Day 12: <see href="https://adventofcode.com/2020/day/12" />
+/// </summary>
+public sealed class Day12 : Day
 {
-    /// <summary>
+    public Day12() : base(12, "Rain Risk")
-    ///     Day 12: <see href="https://adventofcode.com/2020/day/12" />
-    /// </summary>
-    public sealed class Day12 : Day
     {
-        public Day12() : base(12, "Rain Risk")
-        {
-        }
-
-        private static void Swap(ref int x, ref int y)
-        {
-            var tmp = x;
-            x = y;
-            y = tmp;
-        }
-
-        private (int x, int y, int sx, int sy) ProcessInstructions()
-        {
-            // start facing east
-            int x = 0, y = 0, dx = 1, dy = 0;
-            int sx = 0, sy = 0, waypointX = 10, waypointY = -1;
-
-            foreach (var instruction in Input)
-            {
-                var value = int.Parse(instruction[1..]);
-
-                switch (instruction[0])
-                {
-                    case 'N':
-                        y -= value;
-                        waypointY -= value;
-                        break;
-                    case 'S':
-                        y += value;
-                        waypointY += value;
-                        break;
-                    case 'E':
-                        x += value;
-                        waypointX += value;
-                        break;
-                    case 'W':
-                        x -= value;
-                        waypointX -= value;
-                        break;
-                    case 'L':
-                        for (var i = 0; i < value / 90; ++i)
-                        {
-                            Swap(ref dx, ref dy);
-                            Swap(ref waypointX, ref waypointY);
-                            dy *= -1;
-                            waypointY *= -1;
-                        }
-
-                        break;
-                    case 'R':
-                        for (var i = 0; i < value / 90; ++i)
-                        {
-                            Swap(ref dx, ref dy);
-                            Swap(ref waypointX, ref waypointY);
-                            dx *= -1;
-                            waypointX *= -1;
-                        }
-
-                        break;
-                    case 'F':
-                        x += dx * value;
-                        y += dy * value;
-                        sx += waypointX * value;
-                        sy += waypointY * value;
-                        break;
-                    default: throw new InvalidOperationException(nameof(instruction));
-                }
-            }
-
-            return (x, y, sx, sy);
-        }
-
-        public override string Part1()
-        {
-            var (x, y, _, _) = ProcessInstructions();
-            return $"{Math.Abs(x) + Math.Abs(y)}";
-        }
-
-        public override string Part2()
-        {
-            var (_, _, sx, sy) = ProcessInstructions();
-            return $"{Math.Abs(sx) + Math.Abs(sy)}";
-        }
     }
-}
+
+    private static void Swap(ref int x, ref int y)
+    {
+        (y, x) = (x, y);
+    }
+
+    private (int x, int y, int sx, int sy) ProcessInstructions()
+    {
+        // start facing east
+        int x = 0, y = 0, dx = 1, dy = 0;
+        int sx = 0, sy = 0, waypointX = 10, waypointY = -1;
+
+        foreach (var instruction in Input)
+        {
+            var value = int.Parse(instruction[1..]);
+
+            switch (instruction[0])
+            {
+                case 'N':
+                    y -= value;
+                    waypointY -= value;
+                    break;
+                case 'S':
+                    y += value;
+                    waypointY += value;
+                    break;
+                case 'E':
+                    x += value;
+                    waypointX += value;
+                    break;
+                case 'W':
+                    x -= value;
+                    waypointX -= value;
+                    break;
+                case 'L':
+                    for (var i = 0; i < value / 90; ++i)
+                    {
+                        Swap(ref dx, ref dy);
+                        Swap(ref waypointX, ref waypointY);
+                        dy *= -1;
+                        waypointY *= -1;
+                    }
+
+                    break;
+                case 'R':
+                    for (var i = 0; i < value / 90; ++i)
+                    {
+                        Swap(ref dx, ref dy);
+                        Swap(ref waypointX, ref waypointY);
+                        dx *= -1;
+                        waypointX *= -1;
+                    }
+
+                    break;
+                case 'F':
+                    x += dx * value;
+                    y += dy * value;
+                    sx += waypointX * value;
+                    sy += waypointY * value;
+                    break;
+                default: throw new InvalidOperationException(nameof(instruction));
+            }
+        }
+
+        return (x, y, sx, sy);
+    }
+
+    public override string Part1()
+    {
+        var (x, y, _, _) = ProcessInstructions();
+        return $"{Math.Abs(x) + Math.Abs(y)}";
+    }
+
+    public override string Part2()
+    {
+        var (_, _, sx, sy) = ProcessInstructions();
+        return $"{Math.Abs(sx) + Math.Abs(sy)}";
+    }
+}

aoc2020/Day13.cs

@@ -1,54 +1,51 @@
-using System.Linq;
+namespace aoc2020;
 
-namespace aoc2020
+/// <summary>
+///     Day 13: <see href="https://adventofcode.com/2020/day/13" />
+/// </summary>
+public sealed class Day13 : Day
 {
-    /// <summary>
+    private readonly long[] _buses;
-    ///     Day 13: <see href="https://adventofcode.com/2020/day/13" />
+    private readonly long _earliest;
-    /// </summary>
+    private readonly string[] _fullSchedule;
-    public sealed class Day13 : Day
+
+    public Day13() : base(13, "Shuttle Search")
     {
-        private readonly long[] _buses;
+        _earliest = long.Parse(Input.First());
-        private readonly long _earliest;
+        _fullSchedule = Input.Last().Split(',');
-        private readonly string[] _fullSchedule;
+        _buses = _fullSchedule.Where(c => c != "x").Select(long.Parse).ToArray();
+    }
 
-        public Day13() : base(13, "Shuttle Search")
+    public override string Part1()
-        {
+    {
-            _earliest = long.Parse(Input.First());
+        for (var i = _earliest; ; i++)
-            _fullSchedule = Input.Last().Split(',');
+            if (_buses.Any(b => i % b == 0))
-            _buses = _fullSchedule.Where(c => c != "x").Select(long.Parse).ToArray();
-        }
-
-        public override string Part1()
-        {
-            for (var i = _earliest;; i++)
-                if (_buses.Any(b => i % b == 0))
-                {
-                    var bus = _buses.First(b => i % b == 0);
-                    return $"{bus * (i - _earliest)}";
-                }
-        }
-
-        public override string Part2()
-        {
-            var i = 0;
-            long result = 1, multiplier = 1;
-
-            foreach (var id in _fullSchedule)
             {
-                if (id != "x")
+                var bus = _buses.First(b => i % b == 0);
-                {
+                return $"{bus * (i - _earliest)}";
-                    var increment = long.Parse(id);
+            }
-                    while (((result += multiplier) + i) % increment != 0)
+    }
-                    {
-                    }
 
-                    multiplier *= increment;
+    public override string Part2()
+    {
+        var i = 0;
+        long result = 1, multiplier = 1;
+
+        foreach (var id in _fullSchedule)
+        {
+            if (id != "x")
+            {
+                var increment = long.Parse(id);
+                while (((result += multiplier) + i) % increment != 0)
+                {
                 }
 
-                i++;
+                multiplier *= increment;
             }
 
-            return $"{result}";
+            i++;
         }
+
+        return $"{result}";
     }
-}
+}

aoc2020/Day14.cs

@@ -1,111 +1,106 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 14: <see href="https://adventofcode.com/2020/day/14" />
+/// </summary>
+public sealed class Day14 : Day
 {
-    /// <summary>
+    public Day14() : base(14, "Docking Data")
-    ///     Day 14: <see href="https://adventofcode.com/2020/day/14" />
-    /// </summary>
-    public sealed class Day14 : Day
     {
-        public Day14() : base(14, "Docking Data")
+    }
-        {
-        }
 
-        public override string Part1()
+    public override string Part1()
-        {
+    {
-            var writes = new Dictionary<ulong, ulong>();
+        var writes = new Dictionary<ulong, ulong>();
-            ulong mask = 0, bits = 0;
+        ulong mask = 0, bits = 0;
 
-            foreach (var line in Input)
+        foreach (var line in Input)
-                if (line.StartsWith("mask = "))
+            if (line.StartsWith("mask = "))
-                {
-                    var str = line.Split("mask = ", 2)[1];
-                    mask = bits = 0;
-                    for (var i = 35; i >= 0; --i)
-                        switch (str[35 - i])
-                        {
-                            case 'X':
-                                mask |= 1UL << i;
-                                break;
-                            case '1':
-                                bits |= 1UL << i;
-                                break;
-                        }
-                }
-                else
-                {
-                    var spl = line.Split(new[] {'[', ']', '='},
-                            StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
-                        .Skip(1)
-                        .Select(ulong.Parse)
-                        .ToArray();
-
-                    writes[spl[0]] = (spl[1] & mask) | bits;
-                }
-
-            return $"{writes.Aggregate<KeyValuePair<ulong, ulong>, ulong>(0, (current, w) => current + w.Value)}";
-        }
-
-        public override string Part2()
-        {
-            var memory = new Dictionary<ulong, ulong>();
-            var mask = "";
-
-            foreach (var line in Input)
             {
-                var spl = line.Split(' ', 3, StringSplitOptions.TrimEntries);
+                var str = line.Split("mask = ", 2)[1];
-
+                mask = bits = 0;
-                if (spl[0] == "mask")
+                for (var i = 35; i >= 0; --i)
-                {
+                    switch (str[35 - i])
-                    mask = spl[2];
-                }
-                else
-                {
-                    var value = ulong.Parse(spl[2]);
-                    var addr = ulong.Parse(spl[0].Split(new[] {'[', ']'},
-                        StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)[1]);
-
-                    var floats = new List<int>();
-                    for (var i = 0; i < mask.Length; i++)
-                        switch (mask[i])
-                        {
-                            case 'X':
-                                floats.Add(i);
-                                break;
-                            case '1':
-                                addr |= 1UL << (35 - i);
-                                break;
-                        }
-
-                    if (floats.Any())
                     {
-                        var combos = new List<ulong> {addr};
+                        case 'X':
-
+                            mask |= 1UL << i;
-                        foreach (var i in floats)
+                            break;
-                        {
+                        case '1':
-                            var newCombos = new List<ulong>();
+                            bits |= 1UL << i;
-                            foreach (var c in combos)
+                            break;
-                            {
-                                newCombos.Add(c | (1UL << (35 - i)));
-                                newCombos.Add(c & ~(1UL << (35 - i)));
-                            }
-
-                            combos = newCombos;
-                        }
-
-                        foreach (var c in combos)
-                            memory[c] = value;
                     }
-                    else
+            }
-                    {
+            else
-                        memory[addr] = value;
+            {
-                    }
+                var spl = line.Split(new[] { '[', ']', '=' },
-                }
+                        StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
+                    .Skip(1)
+                    .Select(ulong.Parse)
+                    .ToArray();
+
+                writes[spl[0]] = (spl[1] & mask) | bits;
             }
 
-            return $"{memory.Aggregate<KeyValuePair<ulong, ulong>, ulong>(0, (current, w) => current + w.Value)}";
+        return $"{writes.Aggregate<KeyValuePair<ulong, ulong>, ulong>(0, (current, w) => current + w.Value)}";
-        }
     }
-}
+
+    public override string Part2()
+    {
+        var memory = new Dictionary<ulong, ulong>();
+        var mask = "";
+
+        foreach (var line in Input)
+        {
+            var spl = line.Split(' ', 3, StringSplitOptions.TrimEntries);
+
+            if (spl[0] == "mask")
+            {
+                mask = spl[2];
+            }
+            else
+            {
+                var value = ulong.Parse(spl[2]);
+                var addr = ulong.Parse(spl[0].Split(new[] { '[', ']' },
+                    StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)[1]);
+
+                var floats = new List<int>();
+                for (var i = 0; i < mask.Length; i++)
+                    switch (mask[i])
+                    {
+                        case 'X':
+                            floats.Add(i);
+                            break;
+                        case '1':
+                            addr |= 1UL << (35 - i);
+                            break;
+                    }
+
+                if (floats.Any())
+                {
+                    var combos = new List<ulong> { addr };
+
+                    foreach (var i in floats)
+                    {
+                        var newCombos = new List<ulong>();
+                        foreach (var c in combos)
+                        {
+                            newCombos.Add(c | (1UL << (35 - i)));
+                            newCombos.Add(c & ~(1UL << (35 - i)));
+                        }
+
+                        combos = newCombos;
+                    }
+
+                    foreach (var c in combos)
+                        memory[c] = value;
+                }
+                else
+                {
+                    memory[addr] = value;
+                }
+            }
+        }
+
+        return $"{memory.Aggregate<KeyValuePair<ulong, ulong>, ulong>(0, (current, w) => current + w.Value)}";
+    }
+}

aoc2020/Day15.cs

@@ -1,48 +1,45 @@
-using System.Linq;
+namespace aoc2020;
 
-namespace aoc2020
+/// <summary>
+///     Day 15: <see href="https://adventofcode.com/2020/day/15" />
+/// </summary>
+public sealed class Day15 : Day
 {
-    /// <summary>
+    private readonly int[] _turns;
-    ///     Day 15: <see href="https://adventofcode.com/2020/day/15" />
+    private int _current;
-    /// </summary>
+    private int _i;
-    public sealed class Day15 : Day
+
+    public Day15() : base(15, "Rambunctious Recitation")
     {
-        private readonly int[] _turns;
+        var initial = Input.First().Split(',').Select(int.Parse).ToArray();
-        private int _current;
+        _turns = new int[30_000_000];
-        private int _i;
 
-        public Day15() : base(15, "Rambunctious Recitation")
+        // seed array with initial values
-        {
+        for (_i = 1; _i < initial.Length + 1; _i++)
-            var initial = Input.First().Split(',').Select(int.Parse).ToArray();
+            _turns[initial[_i - 1]] = _i;
-            _turns = new int[30_000_000];
-
-            // seed array with initial values
-            for (_i = 1; _i < initial.Length + 1; _i++)
-                _turns[initial[_i - 1]] = _i;
-        }
-
-        public override string Part1()
-        {
-            for (; _i != 2020; _i++)
-            {
-                var next = _turns[_current] > 0 ? _i - _turns[_current] : 0;
-                _turns[_current] = _i;
-                _current = next;
-            }
-
-            return $"{_current}";
-        }
-
-        public override string Part2()
-        {
-            for (; _i != 30_000_000; _i++)
-            {
-                var next = _turns[_current] > 0 ? _i - _turns[_current] : 0;
-                _turns[_current] = _i;
-                _current = next;
-            }
-
-            return $"{_current}";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        for (; _i != 2020; _i++)
+        {
+            var next = _turns[_current] > 0 ? _i - _turns[_current] : 0;
+            _turns[_current] = _i;
+            _current = next;
+        }
+
+        return $"{_current}";
+    }
+
+    public override string Part2()
+    {
+        for (; _i != 30_000_000; _i++)
+        {
+            var next = _turns[_current] > 0 ? _i - _turns[_current] : 0;
+            _turns[_current] = _i;
+            _current = next;
+        }
+
+        return $"{_current}";
+    }
+}

aoc2020/Day16.cs

@@ -1,91 +1,86 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 16: <see href="https://adventofcode.com/2020/day/16" />
+/// </summary>
+public sealed class Day16 : Day
 {
-    /// <summary>
+    private readonly Dictionary<string, List<Range>> _rules;
-    ///     Day 16: <see href="https://adventofcode.com/2020/day/16" />
+    private readonly List<List<int>> _tickets;
-    /// </summary>
+
-    public sealed class Day16 : Day
+    public Day16() : base(16, "Ticket Translation")
     {
-        private readonly Dictionary<string, List<Range>> _rules;
+        _tickets = new();
-        private readonly List<List<int>> _tickets;
+        _rules = new();
 
-        public Day16() : base(16, "Ticket Translation")
+        foreach (var line in Input)
         {
-            _tickets = new List<List<int>>();
+            var spl = line.Split(": ", 2, StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
-            _rules = new Dictionary<string, List<Range>>();
+            if (spl.Length == 2)
-
-            foreach (var line in Input)
             {
-                var spl = line.Split(": ", 2, StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
+                var rule = spl[1].Split(" or ").Select(s =>
-                if (spl.Length == 2)
                 {
-                    var rule = spl[1].Split(" or ").Select(s =>
+                    var r = s.Split('-').Select(int.Parse).ToList();
-                    {
+                    return new Range(r[0], r[1]);
-                        var r = s.Split('-').Select(int.Parse).ToList();
+                }).ToList();
-                        return new Range(r[0], r[1]);
-                    }).ToList();
 
-                    _rules.Add(spl[0], rule);
+                _rules.Add(spl[0], rule);
-                }
+            }
-                else
+            else
-                {
+            {
-                    spl = line.Split(',');
+                spl = line.Split(',');
-                    if (spl.Length > 1)
+                if (spl.Length > 1)
-                        _tickets.Add(spl.Select(int.Parse).ToList());
+                    _tickets.Add(spl.Select(int.Parse).ToList());
-                }
             }
         }
-
-        public override string Part1()
-        {
-            var allValues = _tickets.Skip(1).SelectMany(t => t);
-            var allRules = _rules.Values.SelectMany(r => r);
-            return
-                $"{allValues.Where(t => !allRules.Any(r => r.Contains(t))).Sum()}";
-        }
-
-        public override string Part2()
-        {
-            var ticketFields = _tickets
-                // valid tickets
-                .Where(ticket => ticket
-                    .All(t => _rules.Values
-                        .SelectMany(r => r)
-                        .Any(r => r.Contains(t))))
-                // group by index
-                .SelectMany(inner => inner.Select((item, index) => new {item, index}))
-                .GroupBy(i => i.index, i => i.item)
-                .Select(g => g.ToList())
-                .Select((val, i) => new {Value = val, Index = i})
-                .ToList();
-
-            var matchedRules = _rules
-                // find matching rules and indices
-                .SelectMany(x => ticketFields
-                    .Where(y => y.Value.All(z => x.Value.Any(r => r.Contains(z))))
-                    .Select(y => (x.Key, y.Index))
-                    .ToList())
-                .ToList();
-
-            matchedRules.Sort((a, b) =>
-                matchedRules.Count(x => x.Key == a.Key) - matchedRules.Count(x => x.Key == b.Key));
-
-            while (matchedRules.Any(x => matchedRules.Count(y => y.Key == x.Key) > 1))
-                foreach (var (key, index) in matchedRules.Where(y =>
-                        matchedRules.Count(z => z.Key == y.Key) == 1 &&
-                        matchedRules.Count(z => z.Index == y.Index) > 1))
-                    // filter matches by index
-                    matchedRules = matchedRules
-                        .Where(x => x.Index != index || x.Key == key)
-                        .ToList();
-
-            var departureFields = matchedRules.Where(r => r.Key.StartsWith("departure"));
-
-            return
-                $"{departureFields.Aggregate(1L, (l, match) => l * _tickets.First()[match.Index])}";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        var allValues = _tickets.Skip(1).SelectMany(t => t);
+        var allRules = _rules.Values.SelectMany(r => r);
+        return
+            $"{allValues.Where(t => !allRules.Any(r => r.Contains(t))).Sum()}";
+    }
+
+    public override string Part2()
+    {
+        var ticketFields = _tickets
+            // valid tickets
+            .Where(ticket => ticket
+                .All(t => _rules.Values
+                    .SelectMany(r => r)
+                    .Any(r => r.Contains(t))))
+            // group by index
+            .SelectMany(inner => inner.Select((item, index) => new { item, index }))
+            .GroupBy(i => i.index, i => i.item)
+            .Select(g => g.ToList())
+            .Select((val, i) => new { Value = val, Index = i })
+            .ToList();
+
+        var matchedRules = _rules
+            // find matching rules and indices
+            .SelectMany(x => ticketFields
+                .Where(y => y.Value.All(z => x.Value.Any(r => r.Contains(z))))
+                .Select(y => (x.Key, y.Index))
+                .ToList())
+            .ToList();
+
+        matchedRules.Sort((a, b) =>
+            matchedRules.Count(x => x.Key == a.Key) - matchedRules.Count(x => x.Key == b.Key));
+
+        while (matchedRules.Any(x => matchedRules.Count(y => y.Key == x.Key) > 1))
+            foreach (var (key, index) in matchedRules.Where(y =>
+                    matchedRules.Count(z => z.Key == y.Key) == 1 &&
+                    matchedRules.Count(z => z.Index == y.Index) > 1))
+                // filter matches by index
+                matchedRules = matchedRules
+                    .Where(x => x.Index != index || x.Key == key)
+                    .ToList();
+
+        var departureFields = matchedRules.Where(r => r.Key.StartsWith("departure"));
+
+        return
+            $"{departureFields.Aggregate(1L, (l, match) => l * _tickets.First()[match.Index])}";
+    }
+}

aoc2020/Day17.cs

@@ -1,130 +1,126 @@
-using System.Collections.Generic;
+namespace aoc2020;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 17: <see href="https://adventofcode.com/2020/day/17" />
+/// </summary>
+public sealed class Day17 : Day
 {
-    /// <summary>
+    private readonly Dictionary<(int x, int y, int z), char> _plane;
-    ///     Day 17: <see href="https://adventofcode.com/2020/day/17" />
+    private readonly Dictionary<(int x, int y, int z, int w), char> _plane4;
-    /// </summary>
+
-    public sealed class Day17 : Day
+
+    public Day17() : base(17, "Conway Cubes")
     {
-        private readonly Dictionary<(int x, int y, int z), char> _plane;
+        _plane = new Dictionary<(int x, int y, int z), char>();
-        private readonly Dictionary<(int x, int y, int z, int w), char> _plane4;
+        _plane4 = new Dictionary<(int x, int y, int z, int w), char>();
+        var input = Input.ToList();
 
-
+        for (var x = 0; x < 32; x++)
-        public Day17() : base(17, "Conway Cubes")
-        {
-            _plane = new Dictionary<(int x, int y, int z), char>();
-            _plane4 = new Dictionary<(int x, int y, int z, int w), char>();
-            var input = Input.ToList();
-
-            for (var x = 0; x < 32; x++)
             for (var y = 0; y < 32; y++)
-            for (var z = 0; z < 32; z++)
+                for (var z = 0; z < 32; z++)
-                _plane[(x, y, z)] = '.';
+                    _plane[(x, y, z)] = '.';
 
-            for (var x = 0; x < 32; x++)
+        for (var x = 0; x < 32; x++)
             for (var y = 0; y < 32; y++)
-            for (var z = 0; z < 32; z++)
+                for (var z = 0; z < 32; z++)
-            for (var w = 0; w < 32; w++)
+                    for (var w = 0; w < 32; w++)
-                _plane4[(x, y, z, w)] = '.';
+                        _plane4[(x, y, z, w)] = '.';
 
-            for (var y = 0; y < input.Count; y++)
+        for (var y = 0; y < input.Count; y++)
             for (var x = 0; x < input[y].Length; x++)
                 _plane[(x, y, 0)] = input[y][x];
 
-            for (var y = 0; y < input.Count; y++)
+        for (var y = 0; y < input.Count; y++)
             for (var x = 0; x < input[y].Length; x++)
                 _plane4[(x, y, 0, 0)] = input[y][x];
-        }
-
-        private static int Neighbors(IReadOnlyDictionary<(int x, int y, int z), char> plane, int x, int y, int z)
-        {
-            var neighbors = 0;
-
-            foreach (var i in new[] {-1, 0, 1})
-            foreach (var j in new[] {-1, 0, 1})
-            foreach (var k in new[] {-1, 0, 1})
-            {
-                if (i == 0 && j == 0 && k == 0) continue;
-                if (plane[((x + i) & 31, (y + j) & 31, (z + k) & 31)] == '#') neighbors++;
-            }
-
-            return neighbors;
-        }
-
-        private static Dictionary<(int x, int y, int z), char> Iterate(
-            IReadOnlyDictionary<(int x, int y, int z), char> prev)
-        {
-            var next = new Dictionary<(int x, int y, int z), char>();
-
-            for (var z = 0; z < 32; z++)
-            for (var y = 0; y < 32; y++)
-            for (var x = 0; x < 32; x++)
-            {
-                var active = Neighbors(prev, x, y, z);
-                if (prev[(x, y, z)] == '#')
-                    next[(x, y, z)] = active == 2 || active == 3 ? '#' : '.';
-                else
-                    next[(x, y, z)] = active == 3 ? '#' : '.';
-            }
-
-            return next;
-        }
-
-        private static int Neighbors4(IReadOnlyDictionary<(int x, int y, int z, int w), char> plane, int x, int y,
-            int z, int w)
-        {
-            var neighbors = 0;
-
-            foreach (var i in new[] {-1, 0, 1})
-            foreach (var j in new[] {-1, 0, 1})
-            foreach (var k in new[] {-1, 0, 1})
-            foreach (var l in new[] {-1, 0, 1})
-            {
-                if (i == 0 && j == 0 && k == 0 && l == 0) continue;
-                if (plane[((x + i) & 31, (y + j) & 31, (z + k) & 31, (w + l) & 31)] == '#') neighbors++;
-            }
-
-            return neighbors;
-        }
-
-        private static Dictionary<(int x, int y, int z, int w), char> Iterate4(
-            IReadOnlyDictionary<(int x, int y, int z, int w), char> prev)
-        {
-            var next = new Dictionary<(int x, int y, int z, int w), char>();
-
-            for (var z = 0; z < 32; z++)
-            for (var y = 0; y < 32; y++)
-            for (var x = 0; x < 32; x++)
-            for (var w = 0; w < 32; w++)
-            {
-                var active = Neighbors4(prev, x, y, z, w);
-                if (prev[(x, y, z, w)] == '#')
-                    next[(x, y, z, w)] = active == 2 || active == 3 ? '#' : '.';
-                else
-                    next[(x, y, z, w)] = active == 3 ? '#' : '.';
-            }
-
-            return next;
-        }
-
-        public override string Part1()
-        {
-            var plane = _plane;
-            foreach (var _ in Enumerable.Range(0, 6))
-                plane = Iterate(plane);
-
-            return $"{plane.Values.Count(v => v == '#')}";
-        }
-
-        public override string Part2()
-        {
-            var plane = _plane4;
-            foreach (var _ in Enumerable.Range(0, 6))
-                plane = Iterate4(plane);
-
-            return $"{plane.Values.Count(v => v == '#')}";
-        }
     }
-}
+
+    private static int Neighbors(IReadOnlyDictionary<(int x, int y, int z), char> plane, int x, int y, int z)
+    {
+        var neighbors = 0;
+
+        foreach (var i in new[] { -1, 0, 1 })
+            foreach (var j in new[] { -1, 0, 1 })
+                foreach (var k in new[] { -1, 0, 1 })
+                {
+                    if (i == 0 && j == 0 && k == 0) continue;
+                    if (plane[((x + i) & 31, (y + j) & 31, (z + k) & 31)] == '#') neighbors++;
+                }
+
+        return neighbors;
+    }
+
+    private static Dictionary<(int x, int y, int z), char> Iterate(
+        IReadOnlyDictionary<(int x, int y, int z), char> prev)
+    {
+        var next = new Dictionary<(int x, int y, int z), char>();
+
+        for (var z = 0; z < 32; z++)
+            for (var y = 0; y < 32; y++)
+                for (var x = 0; x < 32; x++)
+                {
+                    var active = Neighbors(prev, x, y, z);
+                    if (prev[(x, y, z)] == '#')
+                        next[(x, y, z)] = active == 2 || active == 3 ? '#' : '.';
+                    else
+                        next[(x, y, z)] = active == 3 ? '#' : '.';
+                }
+
+        return next;
+    }
+
+    private static int Neighbors4(IReadOnlyDictionary<(int x, int y, int z, int w), char> plane, int x, int y,
+        int z, int w)
+    {
+        var neighbors = 0;
+
+        foreach (var i in new[] { -1, 0, 1 })
+            foreach (var j in new[] { -1, 0, 1 })
+                foreach (var k in new[] { -1, 0, 1 })
+                    foreach (var l in new[] { -1, 0, 1 })
+                    {
+                        if (i == 0 && j == 0 && k == 0 && l == 0) continue;
+                        if (plane[((x + i) & 31, (y + j) & 31, (z + k) & 31, (w + l) & 31)] == '#') neighbors++;
+                    }
+
+        return neighbors;
+    }
+
+    private static Dictionary<(int x, int y, int z, int w), char> Iterate4(
+        IReadOnlyDictionary<(int x, int y, int z, int w), char> prev)
+    {
+        var next = new Dictionary<(int x, int y, int z, int w), char>();
+
+        for (var z = 0; z < 32; z++)
+            for (var y = 0; y < 32; y++)
+                for (var x = 0; x < 32; x++)
+                    for (var w = 0; w < 32; w++)
+                    {
+                        var active = Neighbors4(prev, x, y, z, w);
+                        if (prev[(x, y, z, w)] == '#')
+                            next[(x, y, z, w)] = active == 2 || active == 3 ? '#' : '.';
+                        else
+                            next[(x, y, z, w)] = active == 3 ? '#' : '.';
+                    }
+
+        return next;
+    }
+
+    public override string Part1()
+    {
+        var plane = _plane;
+        foreach (var _ in Enumerable.Range(0, 6))
+            plane = Iterate(plane);
+
+        return $"{plane.Values.Count(v => v == '#')}";
+    }
+
+    public override string Part2()
+    {
+        var plane = _plane4;
+        foreach (var _ in Enumerable.Range(0, 6))
+            plane = Iterate4(plane);
+
+        return $"{plane.Values.Count(v => v == '#')}";
+    }
+}

aoc2020/Day18.cs

@@ -1,81 +1,75 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 
-namespace aoc2020
+/// <summary>
+///     Day 18: <see href="https://adventofcode.com/2020/day/18" />
+/// </summary>
+public sealed class Day18 : Day
 {
-    /// <summary>
+    private readonly List<string> _expressions;
-    ///     Day 18: <see href="https://adventofcode.com/2020/day/18" />
+
-    /// </summary>
+    public Day18() : base(18, "Operation Order")
-    public sealed class Day18 : Day
     {
-        private readonly List<string> _expressions;
+        _expressions = Input.Select(line => line.Replace(" ", "")).ToList();
-
-        public Day18() : base(18, "Operation Order")
-        {
-            _expressions = Input.Select(line => line.Replace(" ", "")).ToList();
-        }
-
-        private static long Calculate(string expr, Func<char, int> precedence)
-        {
-            var postfixNotation = new StringBuilder();
-            var postfixStack = new Stack<char>();
-
-            foreach (var c in expr)
-                if (char.IsDigit(c))
-                {
-                    postfixNotation.Append(c);
-                }
-                else if (c == '(')
-                {
-                    postfixStack.Push(c);
-                }
-                else if (c == ')')
-                {
-                    while (postfixStack.Count > 0 && postfixStack.Peek() != '(')
-                        postfixNotation.Append(postfixStack.Pop());
-
-                    postfixStack.TryPop(out _);
-                }
-                else
-                {
-                    while (postfixStack.Count > 0 && precedence(c) <= precedence(postfixStack.Peek()))
-                        postfixNotation.Append(postfixStack.Pop());
-
-                    postfixStack.Push(c);
-                }
-
-            while (postfixStack.Count > 0)
-                postfixNotation.Append(postfixStack.Pop());
-
-            var expressionStack = new Stack<long>();
-
-            foreach (var c in postfixNotation.ToString())
-                if (char.IsDigit(c))
-                {
-                    expressionStack.Push((long) char.GetNumericValue(c));
-                }
-                else
-                {
-                    var a = expressionStack.Pop();
-                    var b = expressionStack.Pop();
-
-                    if (c == '+') expressionStack.Push(a + b);
-                    if (c == '*') expressionStack.Push(a * b);
-                }
-
-            return expressionStack.Pop();
-        }
-
-        public override string Part1()
-        {
-            return $"{_expressions.Sum(expr => Calculate(expr, c => c == '+' || c == '*' ? 1 : 0))}";
-        }
-
-        public override string Part2()
-        {
-            return $"{_expressions.Sum(expr => Calculate(expr, c => c switch {'+' => 2, '*' => 1, _ => 0}))}";
-        }
     }
-}
+
+    private static long Calculate(string expr, Func<char, int> precedence)
+    {
+        var postfixNotation = new StringBuilder();
+        var postfixStack = new Stack<char>();
+
+        foreach (var c in expr)
+            if (char.IsDigit(c))
+            {
+                postfixNotation.Append(c);
+            }
+            else if (c == '(')
+            {
+                postfixStack.Push(c);
+            }
+            else if (c == ')')
+            {
+                while (postfixStack.Count > 0 && postfixStack.Peek() != '(')
+                    postfixNotation.Append(postfixStack.Pop());
+
+                postfixStack.TryPop(out _);
+            }
+            else
+            {
+                while (postfixStack.Count > 0 && precedence(c) <= precedence(postfixStack.Peek()))
+                    postfixNotation.Append(postfixStack.Pop());
+
+                postfixStack.Push(c);
+            }
+
+        while (postfixStack.Count > 0)
+            postfixNotation.Append(postfixStack.Pop());
+
+        var expressionStack = new Stack<long>();
+
+        foreach (var c in postfixNotation.ToString())
+            if (char.IsDigit(c))
+            {
+                expressionStack.Push((long)char.GetNumericValue(c));
+            }
+            else
+            {
+                var a = expressionStack.Pop();
+                var b = expressionStack.Pop();
+
+                if (c == '+') expressionStack.Push(a + b);
+                if (c == '*') expressionStack.Push(a * b);
+            }
+
+        return expressionStack.Pop();
+    }
+
+    public override string Part1()
+    {
+        return $"{_expressions.Sum(expr => Calculate(expr, c => c == '+' || c == '*' ? 1 : 0))}";
+    }
+
+    public override string Part2()
+    {
+        return $"{_expressions.Sum(expr => Calculate(expr, c => c switch { '+' => 2, '*' => 1, _ => 0 }))}";
+    }
+}

aoc2020/Day19.cs

@@ -1,57 +1,51 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text.RegularExpressions;
 
-namespace aoc2020
+/// <summary>
+///     Day 19: <see href="https://adventofcode.com/2020/day/19" />
+/// </summary>
+public sealed class Day19 : Day
 {
-    /// <summary>
+    private readonly string[] _messages;
-    ///     Day 19: <see href="https://adventofcode.com/2020/day/19" />
+    private readonly Dictionary<string, string[][]> _rules;
-    /// </summary>
+    private readonly Stack<string> _stack;
-    public sealed class Day19 : Day
+
+    public Day19() : base(19, "Monster Messages")
     {
-        private readonly string[] _messages;
+        _rules = Input.TakeWhile(l => !string.IsNullOrWhiteSpace(l))
-        private readonly Dictionary<string, string[][]> _rules;
+            .Select(l => l.Split(':'))
-        private readonly Stack<string> _stack;
+            .Select(a => (key: a[0],
-
+                val: a[1].Split('|', StringSplitOptions.RemoveEmptyEntries)
-        public Day19() : base(19, "Monster Messages")
+                    .Select(s => s.Split(' ', StringSplitOptions.RemoveEmptyEntries)).ToArray()))
-        {
+            .ToDictionary(a => a.key, a => a.val);
-            _rules = Input.TakeWhile(l => !string.IsNullOrWhiteSpace(l))
+        _messages = Input.Skip(_rules.Count + 1).ToArray();
-                .Select(l => l.Split(':'))
+        _stack = new Stack<string>();
-                .Select(a => (key: a[0],
-                    val: a[1].Split('|', StringSplitOptions.RemoveEmptyEntries)
-                        .Select(s => s.Split(' ', StringSplitOptions.RemoveEmptyEntries)).ToArray()))
-                .ToDictionary(a => a.key, a => a.val);
-            _messages = Input.Skip(_rules.Count + 1).ToArray();
-            _stack = new Stack<string>();
-        }
-
-        private string MakeRegexExpression(string key)
-        {
-            if (_stack.Count(s => s == key) > 10) return "x";
-            _stack.Push(key);
-            var sub = string.Join("|", _rules[key].Select(test => test.Length switch
-            {
-                1 => test[0][0] == '"' ? test[0].Trim('"') : MakeRegexExpression(test[0]),
-                _ => string.Join(string.Empty, test.Select(MakeRegexExpression))
-            }));
-            _stack.Pop();
-            return _rules[key].Length > 1 ? $"({sub})" : sub;
-        }
-
-        public override string Part1()
-        {
-            var exp = new Regex($"^{MakeRegexExpression("0")}$");
-            return $"{_messages.Count(m => exp.IsMatch(m))}";
-        }
-
-        public override string Part2()
-        {
-            // fix rules 8 and 11
-            _rules["8"] = new[] {new[] {"42"}, new[] {"42", "8"}};
-            _rules["11"] = new[] {new[] {"42", "31"}, new[] {"42", "11", "31"}};
-            var exp = new Regex($"^{MakeRegexExpression("0")}$");
-            return $"{_messages.Count(m => exp.IsMatch(m))}";
-        }
     }
-}
+
+    private string MakeRegexExpression(string key)
+    {
+        if (_stack.Count(s => s == key) > 10) return "x";
+        _stack.Push(key);
+        var sub = string.Join("|", _rules[key].Select(test => test.Length switch
+        {
+            1 => test[0][0] == '"' ? test[0].Trim('"') : MakeRegexExpression(test[0]),
+            _ => string.Join(string.Empty, test.Select(MakeRegexExpression))
+        }));
+        _stack.Pop();
+        return _rules[key].Length > 1 ? $"({sub})" : sub;
+    }
+
+    public override string Part1()
+    {
+        var exp = new Regex($"^{MakeRegexExpression("0")}$");
+        return $"{_messages.Count(m => exp.IsMatch(m))}";
+    }
+
+    public override string Part2()
+    {
+        // fix rules 8 and 11
+        _rules["8"] = new[] { new[] { "42" }, new[] { "42", "8" } };
+        _rules["11"] = new[] { new[] { "42", "31" }, new[] { "42", "11", "31" } };
+        var exp = new Regex($"^{MakeRegexExpression("0")}$");
+        return $"{_messages.Count(m => exp.IsMatch(m))}";
+    }
+}

aoc2020/Day20.cs

@@ -1,183 +1,178 @@
-using System;
+namespace aoc2020;
-using System.Collections.Generic;
-using System.Linq;
 
-namespace aoc2020
+/// <summary>
+///     Day 20: <see href="https://adventofcode.com/2020/day/20" />
+/// </summary>
+public sealed class Day20 : Day
 {
-    /// <summary>
+    private readonly List<Tile> _allPermutations;
-    ///     Day 20: <see href="https://adventofcode.com/2020/day/20" />
+    private readonly List<Tile> _topLefts;
-    /// </summary>
+
-    public sealed class Day20 : Day
+    public Day20() : base(20, "Jurassic Jigsaw")
     {
-        private readonly List<Tile> _allPermutations;
+        var lines = new List<string>();
-        private readonly List<Tile> _topLefts;
+        var tiles = new List<Tile>();
+        var currentTileId = 0;
 
-        public Day20() : base(20, "Jurassic Jigsaw")
+        foreach (var line in Input)
-        {
+            if (line.StartsWith("Tile "))
-            var lines = new List<string>();
-            var tiles = new List<Tile>();
-            var currentTileId = 0;
-
-            foreach (var line in Input)
-                if (line.StartsWith("Tile "))
-                {
-                    currentTileId = int.Parse(line.Split(' ', ':')[1]);
-                }
-                else if (line == "")
-                {
-                    tiles.Add(new(currentTileId, lines.Select(l => l.ToCharArray()).ToArray()));
-                    lines.Clear();
-                }
-                else
-                {
-                    lines.Add(line);
-                }
-
-            if (lines.Any()) tiles.Add(new(currentTileId, lines.Select(l => l.ToCharArray()).ToArray()));
-
-            _allPermutations = tiles.SelectMany(t => t.AllPermutations()).ToList();
-            _topLefts = _allPermutations
-                .Where(t => !_allPermutations.Any(t2 => t.TileId != t2.TileId && t.LeftId == t2.RightId) &&
-                            !_allPermutations.Any(t2 => t.TileId != t2.TileId && t.TopId == t2.BottomId))
-                .ToList();
-        }
-
-        private int Roughness(Tile arg)
-        {
-            var seaMonster = new[]
             {
+                currentTileId = int.Parse(line.Split(' ', ':')[1]);
+            }
+            else if (line == "")
+            {
+                tiles.Add(new(currentTileId, lines.Select(l => l.ToCharArray()).ToArray()));
+                lines.Clear();
+            }
+            else
+            {
+                lines.Add(line);
+            }
+
+        if (lines.Any()) tiles.Add(new(currentTileId, lines.Select(l => l.ToCharArray()).ToArray()));
+
+        _allPermutations = tiles.SelectMany(t => t.AllPermutations()).ToList();
+        _topLefts = _allPermutations
+            .Where(t => !_allPermutations.Any(t2 => t.TileId != t2.TileId && t.LeftId == t2.RightId) &&
+                        !_allPermutations.Any(t2 => t.TileId != t2.TileId && t.TopId == t2.BottomId))
+            .ToList();
+    }
+
+    private int Roughness(Tile arg)
+    {
+        var seaMonster = new[]
+        {
                 "                  # ",
                 "#    ##    ##    ###",
                 " #  #  #  #  #  #   "
             }.Select(s => s.ToArray()).ToArray();
-            
-            const int seaMonsterWidth = 20;
-            const int seaMonsterHeight = 3;
-            const int seaMonsterTiles = 15;
 
-            var placedTiles = new Dictionary<(int x, int y), Tile>();
+        const int seaMonsterWidth = 20;
-            bool NotPlaced(Tile tile) => placedTiles!.Values.All(t => t.TileId != tile.TileId);
+        const int seaMonsterHeight = 3;
-            char Grid(int i, int j) => placedTiles![(i / 8, j / 8)].Pixels[j % 8 + 1][i % 8 + 1];
+        const int seaMonsterTiles = 15;
 
-            bool HasSeaMonster((int x, int y) location)
+        var placedTiles = new Dictionary<(int x, int y), Tile>();
-            {
+        bool NotPlaced(Tile tile) => placedTiles!.Values.All(t => t.TileId != tile.TileId);
-                for (var j = 0; j < seaMonsterHeight; j++)
+        char Grid(int i, int j) => placedTiles![(i / 8, j / 8)].Pixels[j % 8 + 1][i % 8 + 1];
+
+        bool HasSeaMonster((int x, int y) location)
+        {
+            for (var j = 0; j < seaMonsterHeight; j++)
                 for (var i = 0; i < seaMonsterWidth; i++)
                 {
                     if (seaMonster![j][i] == ' ') continue;
                     if (Grid(location.x + i, location.y + j) != '#') return false;
                 }
 
-                return true;
+            return true;
-            }
+        }
 
-            placedTiles[(0, 0)] = arg;
+        placedTiles[(0, 0)] = arg;
-            int x = 1, y = 0;
+        int x = 1, y = 0;
-            while (true)
+        while (true)
+        {
+            placedTiles.TryGetValue((x - 1, y), out var left);
+            placedTiles.TryGetValue((x, y - 1), out var top);
+            if (left == null && top == null) break;
+
+            var firstMatch = _allPermutations
+                .Where(t => (left is null || t.LeftId == left.RightId) &&
+                            (top is null || t.TopId == top.BottomId))
+                .Where(NotPlaced)
+                .FirstOrDefault();
+
+            if (firstMatch is not null)
             {
-                placedTiles.TryGetValue((x - 1, y), out var left);
+                placedTiles[(x, y)] = firstMatch;
-                placedTiles.TryGetValue((x, y - 1), out var top);
+                x++;
-                if (left == null && top == null) break;
-
-                var firstMatch = _allPermutations
-                    .Where(t => (left is null || t.LeftId == left.RightId) &&
-                                (top is null || t.TopId == top.BottomId))
-                    .Where(NotPlaced)
-                    .FirstOrDefault();
-
-                if (firstMatch is not null)
-                {
-                    placedTiles[(x, y)] = firstMatch;
-                    x++;
-                }
-                else
-                {
-                    x = 0;
-                    y++;
-                }
             }
+            else
+            {
+                x = 0;
+                y++;
+            }
+        }
 
-            var gridWidth = placedTiles.Keys.Max(t => t.x) + 1;
+        var gridWidth = placedTiles.Keys.Max(t => t.x) + 1;
-            var gridHeight = placedTiles.Keys.Max(t => t.y) + 1;
+        var gridHeight = placedTiles.Keys.Max(t => t.y) + 1;
 
-            var seaMonsterCount = Enumerable.Range(0, gridWidth * 8 - seaMonsterWidth)
+        var seaMonsterCount = Enumerable.Range(0, gridWidth * 8 - seaMonsterWidth)
-                .SelectMany(_ => Enumerable.Range(0, gridHeight * 8 - seaMonsterHeight), (i, j) => (i, j))
+            .SelectMany(_ => Enumerable.Range(0, gridHeight * 8 - seaMonsterHeight), (i, j) => (i, j))
-                .Count(HasSeaMonster);
+            .Count(HasSeaMonster);
-            
-            if (seaMonsterCount == 0) return 0;
 
-            var roughness = 0;
+        if (seaMonsterCount == 0) return 0;
-            for (var j = 0; j < gridHeight; j++)
+
+        var roughness = 0;
+        for (var j = 0; j < gridHeight; j++)
             for (var i = 0; i < gridWidth; i++)
                 if (Grid(x, y) == '#')
                     roughness++;
 
-            return roughness - seaMonsterCount * seaMonsterTiles;
+        return roughness - seaMonsterCount * seaMonsterTiles;
+    }
+
+    public override string Part1()
+    {
+        return $"{_topLefts.Select(t => t.TileId).Distinct().Aggregate(1L, (acc, next) => acc * next)}";
+    }
+
+    public override string Part2()
+    {
+        return $"{_topLefts.Select(Roughness).First(r => r > 0)}";
+    }
+
+    private record Tile(int TileId, char[][] Pixels)
+    {
+        private const int Size = 10;
+        internal int TopId => GetId(z => (z, 0));
+        internal int BottomId => GetId(z => (z, Size - 1));
+        internal int LeftId => GetId(z => (0, z));
+        internal int RightId => GetId(z => (Size - 1, z));
+
+        private int GetId(Func<int, (int x, int y)> selector)
+        {
+            return Enumerable.Range(0, Size)
+                .Select(selector)
+                .Select((c, i) => (Pixels[c.x][c.y] == '#' ? 1 : 0) << i)
+                .Aggregate(0, (acc, next) => acc | next);
         }
 
-        public override string Part1()
+        private Tile RotateClockwise()
         {
-            return $"{_topLefts.Select(t => t.TileId).Distinct().Aggregate(1L, (acc, next) => acc * next)}";
+            return Transform((x, y, newPixels) => newPixels[x][Size - 1 - y] = Pixels[y][x]);
         }
 
-        public override string Part2()
+        private Tile Flip()
         {
-            return $"{_topLefts.Select(Roughness).First(r => r > 0)}";
+            return Transform((x, y, newPixels) => newPixels[y][Size - 1 - x] = Pixels[y][x]);
         }
 
-        private record Tile(int TileId, char[][] Pixels)
+        private Tile Transform(Action<int, int, char[][]> transformFunc)
         {
-            private const int Size = 10;
+            var newPixels = Enumerable.Repeat(false, Size).Select(_ => new char[Size]).ToArray();
-            internal int TopId => GetId(z => (z, 0));
-            internal int BottomId => GetId(z => (z, Size - 1));
-            internal int LeftId => GetId(z => (0, z));
-            internal int RightId => GetId(z => (Size - 1, z));
 
-            private int GetId(Func<int, (int x, int y)> selector)
+            for (var y = 0; y < Size; y++)
-            {
-                return Enumerable.Range(0, Size)
-                    .Select(selector)
-                    .Select((c, i) => (Pixels[c.x][c.y] == '#' ? 1 : 0) << i)
-                    .Aggregate(0, (acc, next) => acc | next);
-            }
-
-            private Tile RotateClockwise()
-            {
-                return Transform((x, y, newPixels) => newPixels[x][Size - 1 - y] = Pixels[y][x]);
-            }
-
-            private Tile Flip()
-            {
-                return Transform((x, y, newPixels) => newPixels[y][Size - 1 - x] = Pixels[y][x]);
-            }
-
-            private Tile Transform(Action<int, int, char[][]> transformFunc)
-            {
-                var newPixels = Enumerable.Repeat(false, Size).Select(_ => new char[Size]).ToArray();
-
-                for (var y = 0; y < Size; y++)
                 for (var x = 0; x < Size; x++)
                     transformFunc(x, y, newPixels);
 
-                return new(TileId, newPixels);
+            return new(TileId, newPixels);
-            }
+        }
 
-            internal IEnumerable<Tile> AllPermutations()
+        internal IEnumerable<Tile> AllPermutations()
+        {
+            var tile = this;
+            for (var i = 1; i <= 8; i++)
             {
-                var tile = this;
+                yield return tile;
-                for (var i = 1; i <= 8; i++)
+                if (i == 4) tile = Flip();
-                {
+                else if (i == 8) yield break;
-                    yield return tile;
+                tile = tile.RotateClockwise();
-                    if (i == 4) tile = Flip();
-                    else if (i == 8) yield break;
-                    tile = tile.RotateClockwise();
-                }
-            }
-
-            public string Format()
-            {
-                return $"Tile {TileId}:\n{string.Join("\n", Pixels.Select(p => new string(p)))}";
             }
         }
+
+        public string Format()
+        {
+            return $"Tile {TileId}:\n{string.Join("\n", Pixels.Select(p => new string(p)))}";
+        }
     }
-}
+}

aoc2020/Day21.cs

@@ -1,22 +1,21 @@
-namespace aoc2020
+namespace aoc2020;
+
+/// <summary>
+///     Day 21: <see href="https://adventofcode.com/2020/day/21" />
+/// </summary>
+public sealed class Day21 : Day
 {
-    /// <summary>
+    public Day21() : base(21, "Allergen Assessment")
-    ///     Day 21: <see href="https://adventofcode.com/2020/day/21" />
-    /// </summary>
-    public sealed class Day21 : Day
     {
-        public Day21() : base(21, "Allergen Assessment")
-        {
-        }
-
-        public override string Part1()
-        {
-            return "";
-        }
-
-        public override string Part2()
-        {
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return "";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2020/Day22.cs

@@ -1,22 +1,21 @@
-namespace aoc2020
+namespace aoc2020;
+
+/// <summary>
+///     Day 22: <see href="https://adventofcode.com/2020/day/22" />
+/// </summary>
+public sealed class Day22 : Day
 {
-    /// <summary>
+    public Day22() : base(22, "Crab Combat")
-    ///     Day 22: <see href="https://adventofcode.com/2020/day/22" />
-    /// </summary>
-    public sealed class Day22 : Day
     {
-        public Day22() : base(22, "Crab Combat")
-        {
-        }
-
-        public override string Part1()
-        {
-            return "";
-        }
-
-        public override string Part2()
-        {
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return "";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2020/Day23.cs

@@ -1,22 +1,21 @@
-namespace aoc2020
+namespace aoc2020;
+
+/// <summary>
+///     Day 23: <see href="https://adventofcode.com/2020/day/23" />
+/// </summary>
+public sealed class Day23 : Day
 {
-    /// <summary>
+    public Day23() : base(23, "Crab Cups")
-    ///     Day 23: <see href="https://adventofcode.com/2020/day/23" />
-    /// </summary>
-    public sealed class Day23 : Day
     {
-        public Day23() : base(23, "Crab Cups")
-        {
-        }
-
-        public override string Part1()
-        {
-            return "";
-        }
-
-        public override string Part2()
-        {
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return "";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2020/Day24.cs

@@ -1,22 +1,21 @@
-namespace aoc2020
+namespace aoc2020;
+
+/// <summary>
+///     Day 24: <see href="https://adventofcode.com/2020/day/24" />
+/// </summary>
+public sealed class Day24 : Day
 {
-    /// <summary>
+    public Day24() : base(24, "Lobby Layout")
-    ///     Day 24: <see href="https://adventofcode.com/2020/day/24" />
-    /// </summary>
-    public sealed class Day24 : Day
     {
-        public Day24() : base(24, "Lobby Layout")
-        {
-        }
-
-        public override string Part1()
-        {
-            return "";
-        }
-
-        public override string Part2()
-        {
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return "";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2020/Day25.cs

@@ -1,22 +1,21 @@
-namespace aoc2020
+namespace aoc2020;
+
+/// <summary>
+///     Day 25: <see href="https://adventofcode.com/2020/day/25" />
+/// </summary>
+public sealed class Day25 : Day
 {
-    /// <summary>
+    public Day25() : base(25, "Combo Breaker")
-    ///     Day 25: <see href="https://adventofcode.com/2020/day/25" />
-    /// </summary>
-    public sealed class Day25 : Day
     {
-        public Day25() : base(25, "Combo Breaker")
-        {
-        }
-
-        public override string Part1()
-        {
-            return "";
-        }
-
-        public override string Part2()
-        {
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return "";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2020/DayX.cs.txt

@@ -1,22 +1,21 @@
-namespace aoc2020
+namespace aoc2020;
+
+/// <summary>
+///     Day X: <see href="https://adventofcode.com/2020/day/X" />
+/// </summary>
+public sealed class DayX : Day
 {
-    /// <summary>
+    public DayX() : base(X, "")
-    ///     Day X: <see href="https://adventofcode.com/2020/day/X" />
-    /// </summary>
-    public sealed class DayX : Day
     {
-        public DayX() : base(X, "")
-        {
-        }
-
-        public override string Part1()
-        {
-            return "";
-        }
-
-        public override string Part2()
-        {
-            return "";
-        }
     }
-}
+
+    public override string Part1()
+    {
+        return "";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2020/Extensions.cs

@@ -1,28 +1,26 @@
-using System;
 using System.Diagnostics;
 
-namespace aoc2020
+namespace aoc2020;
-{
-    public static class Extensions
-    {
-        /// <summary>
-        ///     increased accuracy for stopwatch based on frequency.
-        ///     <see
-        ///         href="http://geekswithblogs.net/BlackRabbitCoder/archive/2012/01/12/c.net-little-pitfalls-stopwatch-ticks-are-not-timespan-ticks.aspx">
-        ///         blog
-        ///         details here
-        ///     </see>
-        /// </summary>
-        /// <param name="stopwatch"></param>
-        /// <returns></returns>
-        public static double ScaleMilliseconds(this Stopwatch stopwatch)
-        {
-            return 1_000 * stopwatch.ElapsedTicks / (double) Stopwatch.Frequency;
-        }
 
-        public static bool Contains(this Range range, int i)
+public static class Extensions
-        {
+{
-            return i >= range.Start.Value && i <= range.End.Value;
+    /// <summary>
-        }
+    ///     increased accuracy for stopwatch based on frequency.
+    ///     <see
+    ///         href="http://geekswithblogs.net/BlackRabbitCoder/archive/2012/01/12/c.net-little-pitfalls-stopwatch-ticks-are-not-timespan-ticks.aspx">
+    ///         blog
+    ///         details here
+    ///     </see>
+    /// </summary>
+    /// <param name="stopwatch"></param>
+    /// <returns></returns>
+    public static double ScaleMilliseconds(this Stopwatch stopwatch)
+    {
+        return 1_000 * stopwatch.ElapsedTicks / (double)Stopwatch.Frequency;
     }
-}
+
+    public static bool Contains(this Range range, int i)
+    {
+        return i >= range.Start.Value && i <= range.End.Value;
+    }
+}

aoc2020/Program.cs

@@ -1,30 +1,27 @@
-using System;
+using System.Reflection;
-using System.Linq;
-using System.Reflection;
 
-namespace aoc2020
+namespace aoc2020;
+
+internal static class Program
 {
-    internal static class Program
+    private static void Main(string[] args)
     {
-        private static void Main(string[] args)
+        var days = Assembly.GetExecutingAssembly().GetTypes()
-        {
+            .Where(t => t.BaseType == typeof(Day))
-            var days = Assembly.GetExecutingAssembly().GetTypes()
+            .Select(t => Activator.CreateInstance(t) as Day)
-                .Where(t => t.BaseType == typeof(Day))
+            .OrderBy(d => d?.DayNumber);
-                .Select(t => (Day) Activator.CreateInstance(t))
-                .OrderBy(d => d.DayNumber);
 
-            if (args.Length == 1 && int.TryParse(args[0], out var dayNum))
+        if (args.Length == 1 && int.TryParse(args[0], out var dayNum))
-            {
+        {
-                var day = days.FirstOrDefault(d => d.DayNumber == dayNum);
+            var day = days.FirstOrDefault(d => d?.DayNumber == dayNum);
-                if (day != null)
+            if (day != null)
-                    day.AllParts();
+                day.AllParts();
-                else
-                    Console.WriteLine($"Day {dayNum} invalid or not yet implemented");
-            }
             else
-            {
+                Console.WriteLine($"Day {dayNum} invalid or not yet implemented");
-                foreach (var d in days) d.AllParts();
+        }
-            }
+        else
+        {
+            foreach (var d in days) d?.AllParts();
         }
     }
-}
+}

aoc2020/aoc2020.csproj

@@ -1,8 +1,10 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
+	<ImplicitUsings>enable</ImplicitUsings>
+	<Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
@@ -11,4 +13,11 @@
     </None>
   </ItemGroup>
 
+	<ItemGroup>
+		<Using Include="System.Collections.Generic"/>
+		<Using Include="System.Collections.Immutable"/>
+		<Using Include="System.Text"/>
+		<Using Include="System.Text.RegularExpressions"/>
+	</ItemGroup>
+
 </Project>