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).

　　本題和上一題121題的不一樣就是能夠進行屢次買賣，若碰到high>prices[i]則將賣出，並將low和high同時指向i。

代碼：

 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 }