class Solution {public:    int calPoints(vector
     
      & ops) {        vector
      
        v;        for (auto &s : ops) {            if (s == "+") {                v.push_back(v[v.size()-1] + v[v.size()-2]);            }            else if (s == "D") {                v.push_back(v.back() * 2);            }            else if (s == "C") {                v.pop_back();            }            else                v.push_back(stoi(s));        }        int res = 0;        for (auto i : v)            res += i;        return res;    }};