Untitled

class Solution {
public:
    void solve(int open, int close, string ans, vector<string>&res){ //we are decreasing no of open and close left 
        if(open==0 && close==0){
            res.push_back(ans);
            return;
        }

        if(open >0) solve(open-1,close,ans+'(',res); //we can afford more open
        if(close > open) solve(open,close-1,ans+')', res); //we can afford more close

    }

    vector<string> generateParenthesis(int n) {
        int open=n, close=n;
        vector<string> res;
        solve(open,close,"",res);
        return res;
    }
};