122. Best Time to Buy and Sell Stock II

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

Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times). However, you may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

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分析：

神鬼难测的算法。

假设a<b<c<d<e;

则应该返回ans=e-a=(e-d)+(d-c)+(c-b)+(b-a);

假设a<b>c<d<e；

则应该返回ans=e-c+b-a=(e-d)+(d-c)+0+(b-a)；

代码如下：

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