Advent of Code 2024 - Day 19

Mix.install([
  {:kino_aoc, "~> 0.1.7"}
])

Section

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2024", "19", System.fetch_env!("LB_AOC_SESSION"))

[towels, _ | designs] = String.split(puzzle_input, "\n")

towels = String.split(towels, ", ")

defmodule AoC2024.Day19 do
  def run(towels, patterns) do
    Task.async(fn ->
      Enum.map(patterns, &combo(towels, towels, &1))
    end)
    |> Task.await(:infinity)
  end

  defp combo(_, _, "") do
    1
  end

  defp combo([], _, _pattern) do
    0
  end

  defp combo([towel | rest_towels], all_towels, pattern) do
    memoized(pattern, fn ->      
      case pattern do
        ^towel <> rest_pattern ->
          combo1 = combo(all_towels, all_towels, rest_pattern)
          combo2 = combo(rest_towels, all_towels, pattern)
      
          combo1 + combo2
        _ ->
          combo(rest_towels, all_towels, pattern)
      end
    end)
  end

  defp memoized(key, fun) do
    with :miss <- Process.get(key, :miss) do
      fun.() |> tap(&amp;Process.put(key, &amp;1))
    end
  end
end

Part 1

AoC2024.Day19.run(towels, designs)
|> Enum.count(& &1 > 0)

Part 2

AoC2024.Day19.run(towels, designs)
|> Enum.sum()