2015 day 14

AOC.Test/Test2015.cs

@@ -19,6 +19,7 @@ public class Test2015
     [DataRow(typeof(Day11), "hepxxyzz", "heqaabcc")]
     [DataRow(typeof(Day12), "111754", "65402")]
     [DataRow(typeof(Day13), "733", "725")]
+    [DataRow(typeof(Day14), "2655", "1059")]
     public void CheckAllDays(Type dayType, string part1, string part2)
     {
         Common.CheckDay(dayType, part1, part2);

AOC2015/Day13.cs

@@ -7,6 +7,9 @@ namespace AOC2015;
 /// </summary>
 public sealed class Day13 : Day
 {
+    private readonly Dictionary<(string person1, string person2), int> _happinessMap = new();
+    private readonly List<string> _people = new();
+
     public Day13() : base(2015, 13, "Knights of the Dinner Table")
     {
         foreach (var line in Input)
@@ -21,40 +24,36 @@ public sealed class Day13 : Day
     public override object Part2()
     {
         //  Add myself
-        foreach (var person in allPeople)
+        foreach (var person in _people)
         {
-            happinessMap[("me", person)] = 0;
+            _happinessMap[("me", person)] = 0;
-            happinessMap[(person, "me")] = 0;
+            _happinessMap[(person, "me")] = 0;
         }
-        
+
-        allPeople.Add("me");
+        _people.Add("me");
 
         return ComputeHappiness();
     }
 
-    private Dictionary<(string person1, string person2), int> happinessMap = new();
-    private List<string> allPeople = new();
-
     private void AddToHappinessMap(string thisString)
     {
         var tokens = thisString.Split(' ');
-        var firstPerson = tokens.First();
+        var person1 = tokens.First();
-        var lastPerson = tokens.Last().TrimEnd('.');
+        var person2 = tokens.Last().TrimEnd('.');
         var amount = int.Parse(tokens[3]);
 
         if (tokens.Contains("lose"))
             amount *= -1;
 
-        happinessMap[(firstPerson, lastPerson)] = amount;
+        _happinessMap[(person1, person2)] = amount;
 
-        if (!allPeople.Contains(firstPerson))
+        if (!_people.Contains(person1))
-            allPeople.Add(firstPerson);
+            _people.Add(person1);
-        if (!allPeople.Contains(lastPerson))
+        if (!_people.Contains(person2))
-            allPeople.Add(lastPerson);
+            _people.Add(person2);
     }
 
-
+    private static List<List<string>> BuildPermutations(List<string> items)
-    public static List<List<string>> BuildPermutations(List<string> items)
     {
         if (items.Count > 1)
         {
@@ -67,7 +66,7 @@ public sealed class Day13 : Day
 
     public long ComputeHappiness()
     {
-        var possibilities = BuildPermutations(allPeople);
+        var possibilities = BuildPermutations(_people);
 
         var maxHappiness = long.MinValue;
         foreach (var possibility in possibilities)
@@ -81,8 +80,8 @@ public sealed class Day13 : Day
                 var leftPerson = i == 0 ? possibility[^1] : possibility[i - 1];
                 var rightPerson = i == possibility.Count - 1 ? possibility[0] : possibility[i + 1];
 
-                thisPossibilityHappiness += happinessMap[(firstPerson, leftPerson)];
+                thisPossibilityHappiness += _happinessMap[(firstPerson, leftPerson)];
-                thisPossibilityHappiness += happinessMap[(firstPerson, rightPerson)];
+                thisPossibilityHappiness += _happinessMap[(firstPerson, rightPerson)];
             }
 
             maxHappiness = Math.Max(maxHappiness, thisPossibilityHappiness);

AOC2015/Day14.cs

@@ -5,11 +5,36 @@ namespace AOC2015;
 /// </summary>
 public sealed class Day14 : Day
 {
+    private readonly List<Reindeer> _reindeer;
+
     public Day14() : base(2015, 14, "Reindeer Olympics")
     {
+        _reindeer = Input.Select(i => new Reindeer(i)).ToList();
     }
 
-    public override object Part1() => "";
+    public override object Part1() =>
+        _reindeer.Select(r => r.Fly(2503)).Max();
 
-    public override object Part2() => "";
+    public override object Part2() =>
+        Enumerable.Range(1, 2503)
+            .SelectMany(time => _reindeer.GroupBy(r => r.Fly(time)).OrderByDescending(r => r.Key).First())
+            .GroupBy(r => r)
+            .Max(g => g.Count());
+
+    private class Reindeer {
+        private readonly int _duration;
+        private readonly int _rest;
+        private readonly int _speed;
+
+        public Reindeer(string input) {
+            var p = input.Split(' ');
+            _speed = int.Parse(p[3]);
+            _duration = int.Parse(p[6]);
+            _rest = int.Parse(p[13]);
+        }
+
+        public int Fly(int time) =>
+            time / (_duration + _rest) * _speed * _duration // number iterations * travel distance
+            + Math.Min(_duration, time % (_duration + _rest)) * _speed; // last partial iteration
+    }
 }