AOC 2024

Mix.install([{:kino_aoc, "~> 0.1"}])

Day 05

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2024", "5", System.fetch_env!("LB_AOC_SESSION"))

# test_input = Kino.Input.read(test_input)

[rules, updates] =
  puzzle_input
  |> String.split("\n\n")
  |> Enum.map(&String.split(&1, "\n"))

rule_key =
  Enum.reduce(rules, %{}, fn rule, acc ->
    [first_page, other_page] = String.split(rule, "|")

    Map.update(acc, first_page, MapSet.new([other_page]), fn set ->
      MapSet.put(set, other_page)
    end)
  end)

updates
|> Enum.map(&String.split(&1, ","))
|> Enum.filter(fn update ->
  Enum.reduce_while(update, MapSet.new(), fn page, acc ->
    if rule_key |> Map.get(page, MapSet.new()) |> MapSet.disjoint?(acc) do
      {:cont, MapSet.put(acc, page)}
    else
      {:halt, false}
    end
  end)
end)
|> Enum.map(fn pages ->
  pages
  |> Enum.at(pages |> length() |> div(2))
  |> String.to_integer()
end)
|> Enum.sum()