My team isn't exactly doing "top-tier CS work", so if someone "showed off" how far above the average they are with a Coq solution or the quirky GP you replied to or the OP's neural net I'd be delighted and want to skip the rest of the interview, recommending an immediate hire (or at least a go-to-next-stage since I only give these questions over phone screens). The question is beneath them and they have demonstrated that, our team's work is also probably beneath them. We just use that question to filter out the totally unqualified. Their potential value is high because they are overqualified -- they didn't just pass it, they passed it with style. Most dev work at large companies is dull and doesn't require much knowledge that e.g. a CS degree supposedly gives, which is part of why it's amusing/frustrating we have such a bad whiteboard hazing culture insisting candidates can invert a tree or whatever.

I head the "what if they do it this other weird way?" question off by giving them a simple problem, having them solve it (or at least convince me their solution solves it), and then asking them to solve it a different way. My screens mostly follow the ideas from https://sites.google.com/site/steveyegge2/five-essential-pho... I allocate about 10 minutes max for "basic coding" where I just ask them (lately) to write a function that returns true if the given input int (which is assumed to be > 0) is even and false if odd. Then I ask them to do it in different ways. If they use bit-and, I figure they know enough about the "bits and bytes" section too for my team's purposes. Last time someone couldn't recall using bit-and but surprised me with a way I didn't consider, which was convert to string and check the last character. I'm sure there are other ways to do it I haven't considered either. Maybe someone will give me a solution with tensorflow someday, but what would be really impressive is if they bust that out within a few minutes. :) All I'm really after is "can you write code?", if the answer is no then very little time was wasted, if the answer was yes we can go into variations and other questions to rank the other yeses / find other red flags.