[leetcode] 921. Minimum Add to Make Parentheses Valid : https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/

Minimum Add to Make Parentheses Valid.cc

class Solution {
public:
    int minAddToMakeValid(string S) {
        int ans = 0;
        stack<int> s;
        for(int i=0;i<S.size();i++){
            if(S[i] == '(')
                s.push(i);
            else if(s.empty())
                ans++;
            else
                s.pop();
        }
        ans += s.size();
        return ans;
    }
};