Day19

Mix.install([
  {:kino_aoc, git: "https://github.com/ljgago/kino_aoc"}
])

Setup

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

Solve

defmodule Day19 do
  def parse(data) do
    [el, rows] = data |> String.trim() |> String.split("\n\n", trim: true)

    parts = String.split(el, ", ", trim: true) |> MapSet.new()
    max = parts |> Enum.map(fn p -> String.length(p) end) |> Enum.max()

    {parts, String.split(rows, "\n", trim: true), max}
  end

  def solve(data) do
    {parts, rows, max} = parse(data)

    res = Enum.map(rows, &can_match?(&1, parts, max))

    r1 = res |> Enum.reject(&zero?/1) |> Enum.count()
    r2 = Enum.sum(res)

    {r1, r2}
  end

  def zero?(num), do: num == 0

  def can_match?("", _parts, _max), do: 1
  def can_match?(str, parts, max) do
    case :ets.lookup(:cache, str) do
      [] ->
        lim = Enum.min([String.length(str), max])

        res = Enum.reduce(0..lim, 0, fn i, sum ->
            <> <> rest = str
            if head in parts do
              sum + can_match?(rest, parts, max)
            else
              sum
            end
          end)

        :ets.insert(:cache, {str, res})
        res

      [{_key, val}] ->
        val
    end
  end
end

t1 = """
r, wr, b, g, bwu, rb, gb, br

brwrr
bggr
gbbr
rrbgbr
ubwu
bwurrg
brgr
bbrgwb
"""

:ets.new(:cache, [:set, :protected, :named_table])
Day19.solve(t1) |> IO.inspect(label: "t1")
:ets.delete_all_objects(:cache)
Day19.solve(data) |> IO.inspect(label: "data")
:ets.delete(:cache) &amp;&amp; :ok