Maximize profit from one stock trade

Problem

You are given an integer array prices where prices[i] is the price of a stock on day i.

You may complete at most one transaction: choose a day to buy one share and a later day to sell that share.

Return the maximum profit you can achieve. If no profit is possible, return 0.

Input

• prices : array of integers, length n

Output

• An integer: maximum achievable profit

Constraints

• 1 <= n <= 2 * 10^5
• 0 <= prices[i] <= 10^9

Example

• Input: prices = [7,1,5,3,6,4]
• Output: 5 (buy at 1 , sell at 6 )