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).

利用贪心算法，比如 [5, 1, 2, 3, 4]中的1, 2, 3, 4序列来说，对于两种操作方案：
1 在1买入，4卖出
2 在1买入，2卖出同时买入，3卖出同时买入，4卖出
这两种操作下，收益是一样的。

 1 class Solution {
 2 public:
 3     int maxProfit(vector<int>& prices) {
 4         int len=prices.size();
 5         int sum=0;
 6        for (int i = 0; i < len-1; i++)
 7         {
 8             if (prices[i] < prices[i + 1])
 9             {
10                 sum+=prices[i+1]-prices[i];
11             }
12         }
13         return sum;
14     }
15 };

122.Best Time to Buy and Sell Stock II(LeetCode)