123. Best Time to Buy and Sell Stock III

题目

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 at most two transactions.Note:You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

解析

//Buy and Sell Stock iiiclass Solution_123 {public:    int maxProfit(vector
    
      &prices) {        //1.买一次相当于减一个数，        //2.买卖两次维持当前最大的收益        int buy1 = INT_MIN, sell1 = 0;        int buy2 = INT_MIN, sell2 = 0;        for (int i = 0; i < prices.size();i++)        {            buy1 = max(buy1, -prices[i]);            sell1 = max(sell1, buy1 + prices[i]); //一次买卖现有的收益            buy2 = max(buy2, sell1 - prices[i]); //又要使用一些钱            sell2 = max(sell2, buy2 + prices[i]);        }        return sell2;    }};