动态规划
class Solution {
public:
int maxProfit(vector<int>& prices) {
int buy1=-prices[0],sell1=0;
int buy2=-prices[0],sell2=0;
for(int i=0;i<prices.size();i++){
buy1=max(buy1,-prices[i]);//找到第一次买的最小值
sell1=max(sell1,buy1+prices[i]);//找到第一次卖的最大值
buy2=max(buy2,sell1-prices[i]);//找到第二次买的最小值
sell2=max(sell2,buy2+prices[i]);//找到第二次卖的最大值
}
return sell2;
}
};