Day 25 solution

Got global rank 707/592 on this one. My best yet!

src/25.cs

@@ -0,0 +1,92 @@
+namespace aoc2021;
+
+internal class Day25 : Day
+{
+    internal override void Go()
+    {
+        var lines = Util.ReadAllLines("inputs/25.txt");
+        var grid = new byte[lines.Count(), lines.ElementAt(0).Length];
+        for (int i = 0; i < lines.Count(); i++)
+        {
+            var line = lines.ElementAt(i);
+            for (int j = 0; j < line.Length; j++)
+            {
+                if (line[j] == '>')
+                {
+                    grid[i, j] = 1;
+                }
+                else if (line[j] == 'v')
+                {
+                    grid[i, j] = 2;
+                }
+            }
+        }
+        Part1(grid);
+    }
+
+    private static void Part1(byte[,] grid)
+    {
+        using var t = new Timer();
+
+        var xlen = grid.GetLength(0);
+        var ylen = grid.GetLength(1);
+
+        bool stop = false;
+        int step;
+        for (step = 0; !stop; step++)
+        {
+            List<(int x, int y)> toMove = new();
+            for (int i = 0; i < xlen; i++)
+            {
+                for (int j = 0; j < ylen; j++)
+                {
+                    if (grid[i,j] == 1)
+                    {
+                        if (grid[i,(j + 1) % ylen] == 0)
+                        {
+                            toMove.Add((i, j));
+                        }
+                    }
+                }
+            }
+
+            var eastMoves = toMove.Count;
+            foreach (var (x, y) in toMove)
+            {
+                grid[x, (y + 1) % ylen] = grid[x, y];
+                grid[x, y] = 0;
+            }
+            toMove.Clear();
+
+            for (int i = 0; i < xlen; i++)
+            {
+                for (int j = 0; j < ylen; j++)
+                {
+                    if (grid[i, j] == 2)
+                    {
+                        if (grid[(i + 1) % xlen, j] == 0)
+                        {
+                            toMove.Add((i, j));
+                        }
+                    }
+                }
+            }
+
+            if (eastMoves == 0 && !toMove.Any())
+            {
+                stop = true;
+            }
+            else
+            {
+                foreach (var (x, y) in toMove)
+                {
+                    grid[(x + 1) % xlen, y] = grid[x, y];
+                    grid[x, y] = 0;
+                }
+            }
+        }
+
+        t.Stop();
+        Logger.Log($"<+black>> part1: stops at step <+white>{step}<r>");
+    }
+}

src/main.cs

@@ -20,7 +20,7 @@ else
     Day? day = null;
     if (string.IsNullOrEmpty(arg))
     {
-        day = new Day24();
+        day = new Day25();
     }
     else
     {