Problem_Parentheses - xwu36/LeetCode GitHub Wiki

    public List<String> generateParenthesis(int n) {
        List<String> res = new ArrayList<String>();
        dfs("", n, n, res);
        return res;
    }
    
    private void dfs(String s, int left, int right, List<String> res){
        if(left + right == 0) res.add(s);
        if(left > 0) dfs(s + "(", left - 1, right, res);
        if(right > 0 && left < right) dfs(s + ")", left, right - 1, res);
        return;
    }