defmodule MaxProfit do
  def max_profit([first | _] = a) do
    {_min_price, profit} =
      Enum.reduce(a, {first, 0}, fn v, {min_price, profit} ->
        min_price = min(min_price, v)
        {min_price, max(profit, v - min_price)}
      end)

    profit
  end
end