As an interviewer, this is so incredibly frustrating - we don't change our questions often and because of that the questions and answers are all over these forums. With that said, it is incredibly easy to spot someone cheating - they often write the most perfect optimal solution from start to finish, helper functions first, often with the same function names as the forums themselves. The trick I've learned is to ask "why" - "why did you decide to use a linked list for this problem?" - the real cheaters often freeze up and can't give an explanation at all. It's rare, but still too common.
If you've seen the question/answer before just say so! I will totally appreciate the honesty and it goes a long way.
If you've seen the question/answer before just say so! I will totally appreciate the honesty and it goes a long way.