Best Time to Buy and Sell Stock

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

You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the maximum profit you can achieve. If you cannot achieve any profit, return 0.

Example 1:

Input: prices = [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.

Example 2:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: Prices are decreasing, no profit is possible.

Constraints:

• 1 ≤ prices.length ≤ 10⁵
• 0 ≤ prices[i] ≤ 10⁴