Merge pull request #36 from MartinZikmund/feature/aoc2025-day11

Author: MartinZikmund

src/AdventOfCode.Puzzles/2025/11/Part1/Solution.cs

@@ -0,0 +1,40 @@
+namespace AdventOfCode.Puzzles._2025._11.Part1;
+
+public class Solution : IPuzzleSolution
+{
+    private Dictionary<string, string[]> _targets;
+
+    public async Task<string> SolveAsync(StreamReader inputReader)
+    {
+        var lines = await inputReader.ReadAllLinesAsync();
+
+
+        _targets = new Dictionary<string, string[]>();
+        foreach (var line in lines)
+        {
+            var parts = line.Split(": ");
+            var key = parts[0];
+            var values = parts[1].Split(" ", StringSplitOptions.TrimEntries).ToArray();
+            _targets[key] = values;
+        }
+
+        return CountPaths("you").ToString();
+    }
+
+    private int CountPaths(string current)
+    {
+        if (current == "out")
+        {
+            return 1;
+        }
+
+        var targets = _targets[current];
+        var total = 0;
+        foreach (var target in targets)
+        {
+            total += CountPaths(target);
+        }
+
+        return total;
+    }
+}

src/AdventOfCode.Puzzles/2025/11/Part2/Solution.cs

@@ -0,0 +1,73 @@
+using System.Runtime.CompilerServices;
+
+namespace AdventOfCode.Puzzles._2025._11.Part2;
+
+public class Solution : IPuzzleSolution
+{
+    private Dictionary<string, string[]> _targets;
+    private Dictionary<(string node, bool fft, bool dac), ulong> _pathCounts = new();
+
+    public async Task<string> SolveAsync(StreamReader inputReader)
+    {
+        var lines = await inputReader.ReadAllLinesAsync();
+
+
+        _targets = new Dictionary<string, string[]>();
+        foreach (var line in lines)
+        {
+            var parts = line.Split(": ");
+            var key = parts[0];
+            var values = parts[1].Split(" ", StringSplitOptions.TrimEntries).ToArray();
+            _targets[key] = values;
+        }
+
+        var visited = new HashSet<string>();
+        visited.Add("svr");
+        return CountPaths("svr", false, false, visited).ToString();
+    }
+
+    private ulong CountPaths(string current, bool fft, bool dac, HashSet<string> visited)
+    {
+        if (current == "dac")
+        {
+            dac = true;
+        }
+
+        if (current == "fft")
+        {
+            fft = true;
+        }
+
+        if (current == "out")
+        {
+            _pathCounts[("out", fft, dac)] = fft && dac ? 1UL : 0UL;
+            return _pathCounts[("out", fft, dac)];
+        }
+
+        if (!_targets.ContainsKey(current))
+        {
+            return 0;
+        }
+
+        var targets = _targets[current];
+        var total = 0UL;
+
+        foreach (var target in targets.Where(t => !visited.Contains(t)))
+        {
+            visited.Add(target);
+            if (_pathCounts.TryGetValue((target, fft, dac), out var cachedPaths))
+            {
+                total += cachedPaths;
+            }
+            else
+            {
+                var pathsForNode = CountPaths(target, fft, dac, visited);
+                _pathCounts[(target, fft, dac)] = pathsForNode;
+                total += pathsForNode;
+            }
+            visited.Remove(target);
+        }
+
+        return total;
+    }
+}

src/AdventOfCode.Puzzles/2025/11/Part2/TestData.txt

@@ -0,0 +1,13 @@
+svr: aaa bbb
+aaa: fft
+fft: ccc
+bbb: tty
+tty: ccc
+ccc: ddd eee
+ddd: hub
+hub: fff
+eee: dac
+dac: fff
+fff: ggg hhh
+ggg: out
+hhh: out

src/AdventOfCode.Puzzles/2025/11/TestData.txt

@@ -0,0 +1,10 @@
+aaa: you hhh
+you: bbb ccc
+bbb: ddd eee
+ccc: ddd eee fff
+ddd: ggg
+eee: out
+fff: out
+ggg: out
+hhh: ccc fff iii
+iii: out