Day25

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

Setup

{:ok, data} = KinoAOC.download_puzzle("2024", "25", System.fetch_env!("LB_AOC_SECRET"))

Solve

defmodule Day25 do
  def parse(data) do
    data
    |> String.trim()
    |> String.split("\n\n")
    |> Enum.reduce({[], []}, &parse_block/2)
  end

  def parse_block(row, {locks, keys}) do
    data = row
      |> String.split("\n", trim: true)
      |> Enum.map(&String.graphemes/1)

    set = for {r, y} <- Enum.with_index(data),
              {sym, x} <- Enum.with_index(r),
              sym == "#",
              into: MapSet.new(),
              do: {y, x}

    if Enum.all?(hd(data), &amp; &amp;1 == "#") do
      {[set | locks], keys}
    else
      {locks, [set | keys]}
    end
  end

  def solve(data) do
    {locks, keys} = parse(data)

    for lock <- locks, key <- keys do
      MapSet.intersection(lock, key)
    end
    |> Enum.count(fn int -> MapSet.size(int) == 0 end)
  end
end

t1 = """
#####
.####
.####
.####
.#.#.
.#...
.....

#####
##.##
.#.##
...##
...#.
...#.
.....

.....
#....
#....
#...#
#.#.#
#.###
#####

.....
.....
#.#..
###..
###.#
###.#
#####

.....
.....
.....
#....
#.#..
#.#.#
#####
"""

Day25.solve(t1) |> IO.inspect(label: "t1")
Day25.solve(data) #3077