【leetcode】【121】Best Time to Buy and Sell Stock

一、问题描述

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.

二、问题分析

很明显，我们需要找一个最低价买，然后最高价卖呗。前提是最高价在最低价之后。所以可以采用双指针，一个指向低价，一个指向高价。

三、Java AC代码

public int maxProfit(int[] prices) {
if (prices.length==0||prices==null) {
return 0;
}
int minIndex = 0;
int maxIndex = 0;
int maxPro = 0;
for (int i = 1; i < prices.length; i++) {
if (prices[i]<prices[minIndex]) {
minIndex = i;
maxIndex = i;
}
if (prices[i]>prices[maxIndex]) {
maxIndex = i;
maxPro = Math.max(maxPro, prices[i]-prices[minIndex]);
}
}
return maxPro;
}