day 5 part 2

aoc2021.test/DayTests.cs

@@ -8,6 +8,7 @@ public class DayTests
     [DataRow(typeof(Day02), "2272262", "2134882034")]
     [DataRow(typeof(Day03), "3009600", "6940518")]
     [DataRow(typeof(Day04), "8580", "9576")]
+    [DataRow(typeof(Day05), "7318", "19939")]
     public void CheckAllDays(Type dayType, string part1, string part2)
     {
         var s = Stopwatch.StartNew();
@@ -42,7 +43,7 @@ public class DayTests
     [DataRow(typeof(Day02), "150", "900")]
     [DataRow(typeof(Day03), "198", "230")]
     [DataRow(typeof(Day04), "4512", "1924")]
-    [DataRow(typeof(Day05), "5", "")]
+    [DataRow(typeof(Day05), "5", "12")]
     public void CheckTestInputs(Type dayType, string part1, string part2)
     {
         Day.UseTestInput = true;

aoc2021/Day05.cs

@@ -1,82 +1,29 @@
-using System.Drawing;
-
-namespace aoc2021;
+namespace aoc2021;
 
 /// <summary>
 /// Day 5: <see href="https://adventofcode.com/2021/day/5"/>
 /// </summary>
 public sealed class Day05 : Day
 {
-    private readonly List<Line> _lines;
-    
     public Day05() : base(5, "Hydrothermal Venture")
     {
-        _lines = Input.Select(l => new Line(l)).ToList();
     }
 
-    private class Line
-    {
-        public int X1 { get; }
-        public int X2 { get; }
-        public int Y1 { get; }
-        public int Y2 { get; }
+    private int Solve(bool diagonals = false) =>
+        Input
+            .Where(s => !string.IsNullOrEmpty(s))
+            .Select(s => s.Split(" -> "))
+            .Select(a => a.Select(i => i.Split(',')).SelectMany(i => i.Select(int.Parse)).ToList())
+            .Where(t => diagonals || t[0] == t[2] || t[1] == t[3])
+            .SelectMany(t =>
+                Enumerable.Range(0, Math.Max(Math.Abs(t[0] - t[2]), Math.Abs(t[1] - t[3])) + 1)
+                    .Select(i => (
+                        t[0] > t[2] ? t[2] + i : t[0] < t[2] ? t[2] - i : t[2],
+                        t[1] > t[3] ? t[3] + i : t[1] < t[3] ? t[3] - i : t[3])))
+            .GroupBy(k => k)
+            .Count(k => k.Count() > 1);
 
-        public readonly List<Point> AllPoints = new();
-        
-        public Line(string line)
-        {
-            var s = line
-                .Split(" -> ")
-                .Select(i => i.Split(',').Select(int.Parse))
-                .SelectMany(i => i)
-                .ToList();
-            
-            X1 = s[0];
-            X2 = s[1];
-            Y1 = s[2];
-            Y2 = s[3];
+    public override string Part1() => $"{Solve()}";
 
-            if (X1 == X2)
-            {
-                var minY = Math.Min(Y1, Y2);
-                var maxY = Math.Max(Y1, Y2);
-                
-                for (var i = 0; i < maxY - minY; i++)
-                {
-                    AllPoints.Add(new(minY + i, X1));
-                }
-            }
-            else if (Y1 == Y2)
-            {
-                var minX = Math.Min(X1, X2);
-                var maxX = Math.Max(X1, X2);
-
-                for (var i = 0; i < maxX - minX; i++)
-                {
-                    AllPoints.Add(new(minX + i, Y1));
-                }
-            }
-            else
-            {
-                var oX = X1 < X2 ? 1 : -1;
-                var oY = Y1 < Y2 ? 1 : -1;
-                for (var i = 0; i < Math.Abs(X1 - X2); i++)
-                {
-                    AllPoints.Add(new(X1 + i * oX, Y1 + i * oY));
-                }
-            }
-        }
-    }
-
-    public override string Part1()
-    {
-        var groups = _lines
-            .Where(l => l.X1 != l.X2 && l.Y1 != l.Y2)
-            .SelectMany(l => l.AllPoints)
-            .GroupBy(x => x);
-            
-        return $"{groups.Count(g => g.Count() > 1)}";
-    }
-
-    public override string Part2() => "";
+    public override string Part2() => $"{Solve(diagonals: true)}";
 }