121. Best Time to Buy and Sell Stock

题目

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Example 1:Input: [7, 1, 5, 3, 6, 4]Output: 5max. difference = 6-1 = 5 (not 7-1 = 6, as selling price needs to be larger than buying price)

Example 2:

Input: [7, 6, 4, 3, 1]Output: 0In this case, no transaction is done, i.e. max profit = 0.

翻译

假设你有一个数组，其中第i 个元素是第i天给定股票的价格。

如果只允许最多完成一个交易（即购买一个交易并且卖出一个股票），则设计一个算法来找到最大利润。

示例1：
输入：[7，1，5，3，6，4]
输出：5

最大。差= 6-1 = 5（不是7-1 = 6，因为售价需要大于购买价格）
示例2：
输入：[7，6，4，3，1]
输出：0

在这种情况下，没有交易完成，即最大利润= 0。

解题思路

public static int maxProfit(int[] prices) {    int result = 0;    if(prices.length > 0){        int min = prices[0];        for(int i = 1 ; i < prices.length ; i++){            if(prices[i] - min > result)                result = prices[i] - min;            if(prices[i] < min)                min = prices[i];        }    }    return result;}

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