leetcode : Best Time to Buy and Sell Stock II

问题描述：
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).
代码：class Solution {
public:
int maxProfit(vector<int> &prices) {
int ret = 0;
for (int p = 1; p < prices.size(); ++p)
ret += max(prices[p] - prices[p - 1], 0);
return ret;
}
};如果第二天比第一天的价格高，那么就第一天买进，第二天卖出，所得为prices[ i ] - prices[ i - 1 ]；如果第二天比第一天的价格低，那么就第一天买进，第一天卖出，所得为0。以此类推。