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

题目：

可以买卖任意多次，求利润最大值。

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).

解法：

下降到最低点买入，上升到最高点卖出。复杂度O(n)。

代码：

class Solution {public:    int maxProfit(vector<int>& prices) {        int i=0,n=prices.size();        int minn,maxx,res=0;        while(i<n-1)        {            while((i<n-1)&&prices[i]>prices[i+1]) i++;            minn=prices[i];            if(i==n-1) break;            i++;            while((i<n-1)&&prices[i]<prices[i+1]) i++;            maxx=prices[i];            res+=maxx-minn;        }        return res;    }};