day25.exs

defmodule Day25 do
  def actual_program(d, io) do
    a = d
    a = div(a, 2)
    c = rem(a, 2)
    io = [c|io]
    if a == 0 do
      io
    else
      actual_program(a, io)
    end
  end

  def check(io) when rem(length(io), 2) == 0 do
    Enum.all?(Enum.chunk(io, 2), fn(p) -> p == [0, 1] end)
  end
  def check(_), do: false

  def solve() do
    Stream.iterate(0, &(&1 + 1))
    |> Stream.drop_while(fn(a) ->
      d = a + 14 * 182
      not check(actual_program(d, []))
    end)
    |> Enum.take(1)
    |> Enum.at(0)
  end
end