Was that (implement sort) the main point of the question? Especially given the 15 minute time window this sounds more like some kind of fizzbuzz-style question (here's a basic idea, can you translate it to code somehow in some language?). Usually when interviewers give me that kind of thing they're literally fine with bubble-sort (which I'd hope anyone could code on the fly), or even just assuming some appropriately shaped sort function exists and writing the rest of the code around it.