string

    helper(n,0,0,"", &res)

    return res
}

func helper (n int, open int, close int, currentStr string, res *[]string) {
    if open == n && close == n {
        *res = append(*res,currentStr)
        return
    }

    if open < n {
        helper(n, open + 1, close, currentStr + "(", res)
    }
    if open > close {
        helper(n,open, close + 1, currentStr+ ")", res)
    }
}