Best Time to Buy and Sell Stock
You have access to an array where each element represents the price of a specific stock on a given day. Your objective is to maximize profit by selecting one day to purchase the stock and a different, future day to sell it. Determine and return the maximum profit achievable. If it's impossible to generate a profit, return 0.
Input: prices = [9,3,8,2,7,5]
Output: 5
Explanation: Purchase on day 2 (price = 3) and sell on day 5 (price = 7) for a profit of 7 - 3 = 4.