This is an awful interview question. It falls into the same trap that a lot of questions fall into: this is not something that would likely turn up in every-day

This is an awful interview question. It falls into the same trap that a lot of questions fall into: this is not something that would likely turn up in every-day work. Why are you asking a candidate questions about work they will never do? It's also too Computer Science. They're not interviewing for a CS course. They're interviewing to write, debug, maintain and ship code. What you should be exploring is code style, correctness, error catching, and the thought process that goes into it. Expand the question in that manner. Code golf is a very poor signal for a good engineer. Edit: For example, ask "Will this work for all input values of n?". Negative values might have issues, and as 'n' increases it either takes too long to complete or runs out of memory. It's surprising how many candidates don't understand that - and the way this question is asked would not discover it.