Another tip which I give: Interviewers vary widely in how much they care about whether your syntax is accurate, whether you handle invalid inputs, and whether you write unit tests. It's really useful to ask the interviewer whether they want you to worry about those things.
If you handle invalid inputs for an interviewer who doesn't care about that, they're going to be a little annoyed by you going more slowly than needed. If you don't handle invalid inputs for an interviewer who does care, then they'll think you're careless.
If you handle invalid inputs for an interviewer who doesn't care about that, they're going to be a little annoyed by you going more slowly than needed. If you don't handle invalid inputs for an interviewer who does care, then they'll think you're careless.