leetcode

0 class Solution {

1 vector<string> res;

2 stack<char> st;

3 string crnt = "";

4

5 void dfs(int n) {

6 static const char o = '(', c = ')';

7

8 if (!n) {

9 if (st.empty()) res.push_back(crnt);

10 return;

11 }

12

13 st.push(o), crnt += o;

14 dfs(n - 1);

15 st.pop(), crnt.pop_back();

16

17 if (st.empty()) return;

18

19 crnt += c, st.pop();

20 dfs(n - 1);

21 crnt.pop_back();

22 st.push(c);

23 }

24

25 public:

26 vector<string> generateParenthesis(int n) {

27 dfs(n * 2);

28 return res;

29 }

30 };