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).

题目解析：

可以买很多次，求最大收益。

通过画图可以得出，求的是波浪线的上升线段的长度值。所以当a[i]>a[i-1]的时候，res就增加差值。

class Solution {
public:
    int maxProfit(vector<int> &prices) {
        int n = prices.size();
        if(n == 0 || n == 1)
            return 0;

        int res = 0;
        for(int i = 1;i < n;i++){
            if(prices[i] > prices[i-1])
                res += prices[i]-prices[i-1];
        }
        return res;
    }
};