LeetCode - Best Time to Buy and Sell Stock II

Say you have an array for which the i^th 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).

class Solution {public:    int maxProfit(vector<int> &prices) {    if(prices.empty()||prices.size()<=1){        return 0;}int max=0,lowest=prices[0],highest=prices[0],flag=0;//0:待买入，1：待卖出for(int i=1;i<prices.size();i++){if(flag==0){//待买入状态if(prices[i]>lowest){flag=1;highest=prices[i];}else{lowest=prices[i];}}else if(flag==1){//待卖出状态if(prices[i]<highest){flag=0;max+=highest-lowest;lowest=prices[i];highest=prices[i];}else{highest=prices[i];}}}if(flag){max+=highest-lowest;}return max;    }};