Day 05

Mix.install([:kino])

Section

content =
  Kino.FS.file_path("input_05.txt")
  |> File.read!()

[rules, manuals] = content |> String.split("\n\n")

rules =
  rules
  |> String.split(["\n", "|"])
  |> Enum.map(&String.to_integer/1)
  |> Enum.chunk_every(2)
  |> Enum.group_by(&List.first/1, &List.last/1)

manuals =
  manuals
  |> String.split()
  |> Enum.map(fn row -> row |> String.split(",") |> Enum.map(&String.to_integer/1) end)

defmodule Manual do
  def sort(rules, manual) do
    Enum.sort(manual, fn lhs, rhs ->
      rhs in Map.get(rules, lhs, [])
    end)
  end
end

Part 1

manuals
|> Enum.filter(& &1 == Manual.sort(rules, &1))
|> Enum.map(fn list -> Enum.at(list, list |> length |> div(2)) end)
|> Enum.sum()

Part 2

manuals
|> Enum.reject(& &1 == Manual.sort(rules, &1))
|> Enum.map(&Manual.sort(rules, &1))
|> Enum.map(fn list -> Enum.at(list, list |> length |> div(2)) end)
|> Enum.sum()