Leetcode 123. Best Time to Buy and Sell Stock III

 1 class Solution {
 2 public:
 3     int maxProfit(vector<int>& prices) {
 4         int len=prices.size();
 5         //buy1:one buy  buy2:two buy,one sell
 6         //sell1:one buy,one sell  sell2:two buy,two sell
 7         int buy1=INT_MIN,buy2=INT_MIN,sell1=0,sell2=0;
 8         for(int i=0;i<len;i++){
 9             sell1=max(sell1,buy1+prices[i]);
10             buy1=max(buy1,-prices[i]);
11             sell2=max(sell2,buy2+prices[i]);
12             buy2=max(buy2,sell1-prices[i]);
13         }
14         return max(sell1,sell2);
15     }
16 };