Advent of Code 2019 Day16

day16.exs

defmodule Day16 do
  def part2(data) do
    signal = parse(data)

    signal
    |> Enum.reverse()
    |> Stream.cycle()
    |> Stream.take(length(signal) * 10000 - offset(data))
    |> Stream.iterate(fn signal -> Stream.scan(signal, &rem(&1 + &2, 10)) end)
    |> Enum.at(100)
    |> Stream.take(-8)
    |> Enum.reverse()
    |> Enum.join()
  end

  defp parse(data) do
    data
    |> String.trim()
    |> String.split("", trim: true)
    |> Enum.map(&String.to_integer/1)
  end

  defp offset(data) do
    data
    |> String.slice(0, 7)
    |> String.to_integer()
  end
end

IO.puts(Day16.part2(File.read!("data/day16.txt")))