That might be a good thing. It shows how you think in new situations, how you can problem solve, and how you deal with complexity. I used to give "reverse a l

That might be a good thing. It shows how you think in new situations, how you can problem solve, and how you deal with complexity. I used to give "reverse a linked list," and it's essentially a book keeping problem: you're changing links around the time you're trying to read them, so you need to keep all that straight. If there's a bug in their code, you can see the thought process they go through to find and fix it. Unless the job they're interviewing for is almost exactly the same as their current job, it's important to understand how they think through new situations.