【动态规划】Leetcode编程题解：121. Best Time to Buy and Sell Stock Add to List

题目：

Say you have an array for which the i^th element is the price of a given stock on dayi.

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.

样例：

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.

可以通过记录记录当前最小价格并且每次将现阶段价格减去最小价格得到差价，并且保留当前最大差价。

代码：

class Solution {public:    int maxProfit(vector<int>& prices) {        int minFar = INT_MAX;        int maxFar = 0;        for(int i = 0; i < prices.size(); i++) {            minFar = min(minFar, prices[i]);            maxFar = max(maxFar, prices[i] - minFar);        }        return maxFar;    }};

使用Kadane's Algorithm

代码：

class Solution {public:    int maxProfit(vector<int>& prices) {        int maxPro = 0;        int maxFar = 0;        for(int i = 1; i < prices.size(); i++) {            maxPro = max(0, maxPro += prices[i] - prices[i - 1]);            maxFar = max(maxFar, maxPro);        }        return maxFar;    }};