Though the title of this problem is about the "time" to buy and sell stock, the required answer turned out to be the maximum profit possible. So beware!

Buy and Sell stock.md

Problem

You are given an array prices where prices[i] is the price of a given stock on the ith 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 from this transaction. 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.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.

Example 2:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transactions are done and the max profit = 0.

Constraints:

• 1 <= prices.length <= 10^5
• 0 <= prices[i] <= 10^4

maximumProfit.java

class Solution {
    public int maxProfit(int[] prices) {
        int bestProfit = 0;
		int buyIndex = 0;
		int sellIndex = buyIndex + 1;
		
		while (sellIndex < prices.length) {
			int currentProfit = prices[sellIndex] - prices[buyIndex];
			if (currentProfit <= 0) {
				buyIndex++;
			}
			
			bestProfit = Math.max(bestProfit, currentProfit);
			sellIndex++;
		}
		
		return bestProfit;
    }
}