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).

買賣股票的最好時機，題目要求再賣之前必須先購買股票。所以只需要在遍歷價格數組時，碰到相鄰元素順序時求他們的差值後累加即可。

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        if (prices.size() == 0 || prices.size() == 1)
            return 0;
        int res = 0;
        for (int i = 1; i != prices.size(); i++)
            if (prices[i - 1
 
] < prices[i])
                res += (prices[i] - prices[i - 1]);
        return res;
    }
};
// 6 ms

[LeetCode] Best Time to Buy and Sell Stock II