121. Best Time to Buy and Sell Stock

难度: Easy

题目描述

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 <= 105
• 0 <= prices[i] <= 104

解题思路

代码实现

解决方案

java

class Solution {
    public int maxProfit(int[] prices) {
        int maxProfit = 0;
        int purchaseIndex = 0;
        for (int i = 1; i < prices.length; i++) {
            if (prices[i] < prices[purchaseIndex]) {
                purchaseIndex = i;
                continue;
            }
            int getProfit = prices[i] - prices[purchaseIndex];
            if (getProfit > maxProfit) {
                maxProfit = getProfit;
            }
        }

        return maxProfit;

    }
}