122. Best Time to Buy and Sell Stock II

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

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).

　　本题和上一题121题的不一样就是能够进行屡次买卖，若碰到high>prices[i]则将卖出，并将low和high同时指向i。

代码：

 1 int maxProfit(vector<int>& prices)
 2 {
 3     if (prices.size()==0||prices.size()==1)
 4         return 0;
 5     int low=prices[0],high=prices[0],profit=0;
 6     for (int i=1;i<prices.size();i++)
 7     {
 8         if (prices[i]>high)
 9             high=prices[i];
10         else
11         {
12             profit+=high-low;
13             low=prices[i];
14             high=prices[i];
15         }
16     }
17     profit+=high-low;
18     return profit;
19 }