题目描述

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.

分析

输入用例

1. 递减， [5,4,3,2,1]
2. 递增， [1,2,3,4,5]
3. 有增有减

定义int型变量lowest，存储从prices[0..i]的最小值

maxProfit = Math.max(maxProfit, prices[i] – lowest)

代码

    public static int maxProfit(int[] prices) {

        if (prices.length == 0 || prices.length == 1) {
            return 0;
        }

        int maxProfit = 0;
        int lowest = Integer.MAX_VALUE;

        for (int v : prices) {
            lowest = Math.min(v, lowest);
            maxProfit = Math.max(maxProfit, v - lowest);
        }

        return maxProfit;

    }