#121 Best Time to Buy and Sell Stock

Description

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.

Examples

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] <= $10^4$

思路

这没什么好说的……存max和min迭代更新就好了

代码

class Solution {
    public int maxProfit(int[] prices) {
        int min = Integer.MAX_VALUE;
        int max = 0;
        
        for (int i = 0; i < prices.length; i++) {
            min = Math.min(min, prices[i]);
            max = Math.max(max, prices[i] - min);
        }
        
        return max;
    }
}