class Solution {
    List<String> res = new ArrayList<>();

    public void dfs(int n, int lc, int rc, String s){
        if(lc == n && rc == n){
            res.add(s);
            return ;
        }   

        if(lc < n) dfs(n, lc + 1, rc, s + "(");
        if(rc < n && rc < lc) dfs(n, lc, rc + 1, s + ")");
    }

    public List<String> generateParenthesis(int n) {
        dfs(n, 0, 0, "");

        return res;
    }
}