Day 12 solution

This was my initial solution I used to submit the puzzle answer. Runtime for part 2 on my input set was around a second, so now I'm going to find optimization targets. I'm sure there's a lot I could be doing much better.

advent-of-code-2021.csproj

@@ -51,6 +51,9 @@
 	  <None Update="inputs\11.txt">
 	    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
 	  </None>
+	  <None Update="inputs\12.txt">
+	    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+	  </None>
 	</ItemGroup>
 
 </Project>

inputs/12.txt

@@ -0,0 +1,24 @@
+rf-RL
+rf-wz
+wz-RL
+AV-mh
+end-wz
+end-dm
+wz-gy
+wz-dm
+cg-AV
+rf-AV
+rf-gy
+end-mh
+cg-gy
+cg-RL
+gy-RL
+VI-gy
+AV-gy
+dm-rf
+start-cg
+start-RL
+rf-mh
+AV-start
+qk-mh
+wz-mh

src/12.cs

@@ -0,0 +1,93 @@
+namespace aoc2021;
+
+internal class Day12
+{
+    internal static void Go()
+    {
+        Logger.Log("Day 12");
+        Logger.Log("-----");
+        var lines = File.ReadAllLines("inputs/12.txt");
+        var paths = new Dictionary<string, List<string>>();
+        foreach (var line in lines)
+        {
+            var points = line.Split('-');
+            if (!paths.ContainsKey(points[0]))
+            {
+                paths[points[0]] = new List<string>();
+            }
+            if (!paths.ContainsKey(points[1]))
+            {
+                paths[points[1]] = new List<string>();
+            }
+
+            paths[points[0]].Add(points[1]);
+            paths[points[1]].Add(points[0]);
+        }
+        Part1(paths);
+        Part2(paths);
+        Logger.Log("");
+    }
+
+    private static void Part1(Dictionary<string, List<string>> paths)
+    {
+        using var t = new Timer();
+
+        var validPaths = new List<List<string>>();
+        FindPaths(paths, validPaths, new List<string>(){ "start" }, false);
+
+        Logger.Log($"part1: {validPaths.Count}");
+    }
+
+    private static void FindPaths(Dictionary<string, List<string>> paths, List<List<string>> routes, List<string> currRoute, bool canVisitSmallCaveTwice)
+    {
+        //Logger.Log($"Current path: {string.Join(',', currRoute)}");
+        var curr = currRoute.Last();
+        foreach (var next in paths[curr])
+        {
+            //Logger.Log($"  Evaluating next: {next}");
+            if (next == "start")
+            {
+                //Logger.Log($"    is start, skipping");
+                continue;
+            }
+            if (next != "end" && next.ToLower() == next && currRoute.Contains(next))
+            {
+                if (!canVisitSmallCaveTwice)
+                {
+                    //Logger.Log($"    is already-visited small cave, skipping");
+                    continue;
+                }
+                else if (currRoute.Any(x => x.ToLower() == x && currRoute.Count(y => x == y) == 2))
+                {
+                    //Logger.Log($"    is already-visited small cave and we have already been to another one twice, skipping");
+                    continue;
+                }
+            }
+            //Logger.Log($"    adding to route");
+            currRoute.Add(next);
+            if (next == "end")
+            {
+                //Logger.Log($"    is end, so adding {string.Join(',', currRoute)} to valid paths");
+                routes.Add(currRoute);
+            }
+            else
+            {
+                FindPaths(paths, routes, new List<string>(currRoute), canVisitSmallCaveTwice);
+            }
+
+            currRoute.RemoveAt(currRoute.Count - 1);
+        }
+
+        //Logger.Log("  done with route");
+    }
+
+    private static void Part2(Dictionary<string, List<string>> paths)
+    {
+        using var t = new Timer();
+
+        var validPaths = new List<List<string>>();
+        FindPaths(paths, validPaths, new List<string>() { "start" }, true);
+
+        Logger.Log($"part2: {validPaths.Count}");
+    }
+}

src/main.cs

@@ -37,7 +37,11 @@ switch (arg)
         aoc2021.Day10.Go();
         break;
 
-    default:
+    case "11":
         aoc2021.Day11.Go();
         break;
+
+    default:
+        aoc2021.Day12.Go();
+        break;
 }