No, the expectation is that you'll use a loop or recursion. If you use an existing method/function, the interviewer will kindly ask you to implement that yours

No, the expectation is that you'll use a loop or recursion. If you use an existing method/function, the interviewer will kindly ask you to implement that yourself. The general reason why such a question is asked is because interviewers don't have an infinite amount of time and there's no point in considering any candidate who can't do this. It's a way to weed out ridiculously bad candidates so that you can focus more on good candidates.