memoriesadrift

["+3", "+3", "+4", "-2", "-4"] # example input
  |> Enum.map(&String.to_integer/1)
  |> Stream.cycle()
  |> Stream.scan(&(&1 + &2))
  |> Enum.reduce_while(MapSet.new([0]), fn x, acc ->
    if MapSet.member?(acc, x), do: {:halt, x}, else: {:cont, MapSet.put(acc, x)}
  end)