Day Four

Mix.install([
  {:kino, "~> 0.7.0"}
])

Section

input = Kino.Input.textarea("Input")

defmodule DayFour do
  def solve1(input) do
    input
    |> String.split("\n", trim: true)
    |> Enum.map(&parse/1)
    |> Enum.filter(&fully_overlap?/1)
    |> length()
  end

  def solve2(input) do
    input
    |> String.split("\n", trim: true)
    |> Enum.map(&parse/1)
    |> Enum.filter(&any_overlap?/1)
    |> length()
  end

  defp parse(s) do
    s
    |> String.split(",")
    |> Enum.map(fn s ->
      s
      |> String.split("-")
      |> Enum.map(&String.to_integer/1)
    end)
  end

  defp fully_overlap?([[a1, b1], [a2, b2]]) do
    (a1 <= a2 && b1 >= b2) || (a2 <= a1 && b2 >= b1)
  end

  defp any_overlap?([[a1, b1] = p1, [a2, b2] = p2]) do
    fully_overlap?([p1, p2]) ||
      (a1 <= a2 && b1 >= a2) || (a2 <= a1 && b2 >= a1)
  end
end

DayFour.solve2(Kino.Input.read(input))