class Solution {
    public List<String> generateParenthesis(int n) {
        List<String> result = new ArrayList<>();
        // no of opening and closing brackets
        int open = n;
        int close = n;
        findBalancedParenthesis(open, close, result, "");
        return result;
    }

    public void findBalancedParenthesis(int open, int close, List<String> result, String temp)
    {
        // base condition: when both opening and closing brackets is finished, so valid string
        if(open == 0 && close == 0)
        {
            result.add(temp);
            return;
        }

        // choice of opening bracket
        if(open != 0)
        {
            findBalancedParenthesis(open-1, close, result, temp + '(');
        }

        // choice of closing bracket
        if(close > open)
        {
            findBalancedParenthesis(open, close-1, result, temp + ')');
        }
    }
}