AOC 2025/11

namespace AdventOfCode.Y2025.Day11;

[ProblemName("Reactor")]
class Solution : Solver
{

	public long PartOne(string input)
	{
		return CountPaths(Parse(input), "you", "out", [], true, true);
	}

	public long? PartTwo(string input)
	{
		return CountPaths(Parse(input), "svr", "out", []);
	}

	static Dictionary<string, List<string>> Parse(string input)
    {
        Dictionary<string, List<string>> graph = [];

		var lines = input.Split('\n');

		foreach (var line in lines)
		{
			var parts = line.Split(' ');
			graph[parts[0].Split(':')[0]] = parts[1..parts.Length].ToList();
			foreach (var p in parts[1..parts.Length])
			{
				if (!graph.ContainsKey(p))
				{
					graph[p] = [];
				}
			}
		}
		return graph;
    }


	static Dictionary<(string, string, HashSet<string>, bool, bool), long> memo = [];
	private static long CountPaths(Dictionary<string, List<string>> graph, string current, string target, HashSet<string> visited, bool dac = false, bool fft = false)
	{
		if (memo.TryGetValue((current, target, visited, dac, fft), out long res))
		{
			return res;
		}

		if (current == "dac")
			dac = true;
		if (current == "fft")
			fft = true;

		if (string.Equals(current, target, StringComparison.Ordinal))
		{
			if (dac && fft)
			{
				return 1;
			}
			return 0;
		}

		if (visited.Contains(current))
			return 0;

		visited.Add(current);

		long total = 0;
		if (graph.TryGetValue(current, out var neighbors))
		{
			foreach (var n in neighbors)
			{
				total += CountPaths(graph, n, target, visited, dac, fft);
			}
		}

		visited.Remove(current);
		memo[(current, target, visited, dac, fft)] = total;
		return total;
	}

}