@AoKSolution
object Day11 {
    val graph = MapParser { line ->
        val nodes = line.split(": ", " ")
        put(nodes.first(), nodes.drop(1))
    }

    fun Map<String, List<String>>.countPaths(
        start: String, end: String,
        cache: MutableMap<String, Long> = mutableMapOf()
    ): Long = cache.getOrPut(start) {
        if (start == end) 1 else get(start).orEmpty().sumOf { countPaths(it, end, cache) }
    }

    context(_: PuzzleInput)
    fun part1() = graph().countPaths("you", "out")

    context(_: PuzzleInput)
    fun part2() = graph { graph ->
        listOf("svr", "fft", "dac", "out")
            .zipWithNext { start, end -> graph.countPaths(start, end) }
            .reduce(Long::times)
    }
}