defmodule AOC.Day1 do
  def part1 do
    l = AOC.Util.input_integers(1, 1)
    [x, y] = Enum.filter(l, &((2020 - &1) in l))
    x * y
  end

  def find_three([h | tl]) do
    case Enum.filter(tl, &((2020 - h - &1) in tl)) do
      [x, y] -> h * x * y
      _ -> find_three(tl)
    end
  end

  def part2 do
    AOC.Util.input_integers(1, 1)
    |> find_three()
  end
end