Day 17 advent of code

day17.exs

defmodule AoC.Day17 do
  def part1(n) do
    part1([0], 0, 0, n)
    |> Enum.drop_while(&( &1 != 2017 ))
    |> Enum.at(1)
  end

  defp part1(buffer, _, 2017, _), do: buffer
  defp part1(buffer, current_index, iteration, n) do
    current_index = rem(current_index + n, iteration + 1) + 1

    buffer = Enum.take(buffer, current_index) ++ [iteration + 1] ++ Enum.drop(buffer, current_index)

    part1(
      buffer,
      current_index,
      iteration + 1,
      n
    )
  end

  def part2(n) do
    part2(-1, 0, 0, n)
  end

  defp part2(value, current_index, 50_000_000, n), do: value
  defp part2(value, current_index, iteration, n) do
    current_index = rem(current_index + n, iteration + 1) + 1

    value = if current_index == 1, do: iteration + 1, else: value

    part2(value, current_index, iteration + 1, n)
  end
end


AoC.Day17.part1(371)
|> IO.inspect(label: "part 1")

AoC.Day17.part2(371)
|> IO.inspect(label: "part 2")