defmodule Nesting do
  def nesting(""), do: 1

  def nesting(s) do
    result =
      s
      |> String.graphemes()
      |> Enum.reduce_while([], fn ch, stack ->
        case ch do
          ")" ->
            case stack do
              ["(" | rest] -> {:cont, rest}
              _ -> {:halt, :fail}
            end

          other ->
            {:cont, [other | stack]}
        end
      end)

    if result == [], do: 1, else: 0
  end
end