need improve123. Best Time to Buy and Sell Stock III

//很有意思的一道题，暂时没有做透，mark一下
class Solution {
public:
int maxProfit(vector<int>& prices) {
vector<int> res(4, 0);
res[0] = INT_MIN;
res[2] = INT_MIN;
//cout<<res[0]<<" "<<res[1]<<" "<<res[2]<<" "<<res[3]<<"   ";
for(int i = 0; i < prices.size(); ++i) {
res[3]=max(res[3],res[2]+prices[i]);
res[2]=max(res[2],res[1]-prices[i]);
res[1]=max(res[1],prices[i]+res[0]);
res[0]=max(res[0],-prices[i]);
//cout<<res[0]<<" "<<res[1]<<" "<<res[2]<<" "<<res[3]<<"   ";
}
return res[3];
}
};