Day 22. Finally kinda happy with this one, copied code notwithstanding

2020.csproj

@@ -65,6 +65,9 @@
     <None Update="21input.txt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="22input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>

22input.txt

@@ -0,0 +1,53 @@
+Player 1:
+8
+19
+46
+11
+36
+10
+35
+9
+24
+22
+50
+1
+34
+7
+18
+28
+3
+38
+43
+2
+6
+42
+23
+12
+20
+
+Player 2:
+39
+27
+44
+29
+5
+48
+30
+32
+15
+31
+14
+21
+49
+17
+45
+47
+16
+26
+33
+25
+13
+41
+4
+40
+37

Program.cs

@@ -23,6 +23,7 @@
          Q18.Go();
          Q19.Go();
          Q21.Go();
+         Q22.Go();
          Util.Log($"Total time={(System.DateTime.Now - start).TotalMilliseconds}ms");
       }
    }

Q22.cs

@@ -0,0 +1,158 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+
+namespace _2020
+{
+   class Q22
+   {
+      static Dictionary<int, List<int>> list = new Dictionary<int, List<int>>();
+
+      public static void Go()
+      {
+         var start = DateTime.Now;
+         MakeList();
+         Util.Log($"Q22 MakeList took {(DateTime.Now - start).TotalMilliseconds}ms");
+         var p1start = DateTime.Now;
+         Part1();
+         Util.Log($"Q22 part1 took {(DateTime.Now - p1start).TotalMilliseconds}ms");
+         var p2start = DateTime.Now;
+         Part2();
+         Util.Log($"Q22 part2 took {(DateTime.Now - p2start).TotalMilliseconds}ms");
+
+         Util.Log($"Q22 took {(DateTime.Now - start).TotalMilliseconds}ms");
+      }
+
+      static void MakeList()
+      {
+         var currPlayer = 0;
+         foreach (var line in File.ReadAllLines("22input.txt"))
+         {
+            if (line.StartsWith("Player "))
+            {
+               currPlayer = Convert.ToInt32(line["Player ".Length..^1]);
+               list.Add(currPlayer, new List<int>());
+            }
+            else if (string.IsNullOrWhiteSpace(line))
+            {
+               continue;
+            }
+            else
+            {
+               list[currPlayer].Add(Convert.ToInt32(line));
+            }
+         }
+      }
+
+      static void Part1()
+      {
+         var p1deck = new List<int>(list[1]);
+         var p2deck = new List<int>(list[2]);
+         while (p1deck.Any() && p2deck.Any())
+         {
+            var p1card = p1deck.First();
+            p1deck.RemoveAt(0);
+            var p2card = p2deck.First();
+            p2deck.RemoveAt(0);
+            if (p1card > p2card)
+            {
+               p1deck.Add(p1card);
+               p1deck.Add(p2card);
+            }
+            else
+            {
+               p2deck.Add(p2card);
+               p2deck.Add(p1card);
+            }
+         }
+
+         var winner = p1deck.Count == 0 ? p2deck : p1deck;
+         var score = 0;
+         for (int i = winner.Count - 1; i >= 0; i--)
+         {
+            score += (i + 1) * winner[winner.Count - i - 1];
+         }
+
+         Util.Log($"Q22Part1: score={score}");
+      }
+
+      static int gameNum = 0;
+      static int deepestLevel = 0;
+      static int currLevel = 0;
+      static int PlayRecursiveGame(List<int> p1deck, List<int> p2deck)
+      {
+         gameNum++;
+         currLevel++;
+         if (currLevel > deepestLevel)
+         {
+            deepestLevel = currLevel;
+         }
+
+         var p1prev = new List<List<int>>();
+         var p2prev = new List<List<int>>();
+         while (p1deck.Any() && p2deck.Any())
+         {
+            if (p1prev.Any(x => Enumerable.SequenceEqual(p1deck, x)) && p2prev.Any(x => Enumerable.SequenceEqual(p2deck, x)))
+            {
+               currLevel--;
+               return 1;
+            }
+
+            p1prev.Add(new List<int>(p1deck));
+            p2prev.Add(new List<int>(p2deck));
+
+            var p1card = p1deck.First();
+            p1deck.RemoveAt(0);
+            var p2card = p2deck.First();
+            p2deck.RemoveAt(0);
+            if (p1deck.Count >= p1card && p2deck.Count >= p2card)
+            {
+               var winner = PlayRecursiveGame(new List<int>(p1deck.Take(p1card)), new List<int>(p2deck.Take(p2card)));
+               if (winner == 1)
+               {
+                  p1deck.Add(p1card);
+                  p1deck.Add(p2card);
+               }
+               else
+               {
+                  p2deck.Add(p2card);
+                  p2deck.Add(p1card);
+               }
+            }
+            else
+            {
+               if (p1card > p2card)
+               {
+                  p1deck.Add(p1card);
+                  p1deck.Add(p2card);
+               }
+               else
+               {
+                  p2deck.Add(p2card);
+                  p2deck.Add(p1card);
+               }
+            }
+         }
+
+         currLevel--;
+
+         return p1deck.Any() ? 1 : 2;
+      }
+
+      static void Part2()
+      {
+         var winner = PlayRecursiveGame(list[1], list[2]);
+
+         var score = 0;
+         var winnerDeck = list[winner];
+         for (int i = winnerDeck.Count - 1; i >= 0; i--)
+         {
+            score += (i + 1) * winnerDeck[winnerDeck.Count - i - 1];
+         }
+
+         Util.Log($"Q22Part2: games played={gameNum}, deepest level={deepestLevel}, score={score}");
+      }
+   }
+}