# Maximize Profit with One Stock Transaction Implement `max_profit(prices)` for daily integer prices. Choose at most one buy followed by one later sell and return the maximum nonnegative profit. Return `0` when no profitable trade exists. Constraints: up to `200000` prices; each price is an integer in `[0, 10^12]`. The returned profit is a signed 64-bit integer and is guaranteed not to exceed `2^53 - 1`, so all four language implementations represent it exactly. Aim for `O(n)` time and `O(1)` space. ```hint Respect transaction order Test cases include a decreasing series and a low price that appears only after the best selling opportunity. ```