C++

1class Solution {
2  public:
3    string removeOuterParentheses(string s) {
4      bool opened = false;
5      string res = "";
6      int cnt=0;
7
8      for(char c : s) {
9        if(c==40) {
10          if(opened) res+=c, ++cnt;
11          else opened = true;
12        } else if(c == 41) {
13          if(cnt==0) opened = false;
14          else res+=c, --cnt;
15        }
16      }
17
18      return res;
19    }
20};