I've been asked bit twiddling in O(log n) questions before and it was in no way supposed to be a test of my knowledge. It was a way for the interviewer to eval

I've been asked bit twiddling in O(log n) questions before and it was in no way supposed to be a test of my knowledge. It was a way for the interviewer to evaluate my ability to not know how to answer a question. It took me almost an hour to solve, but it gave the interviewer a pretty clear insight into my ability to approach something new. In my experience the best interview questions I've had have been situations where I was asked a question about something I was not familiar with. The interviewer then gave me a 5 minute overview of the things I need to know (like which synchronization methods are available in pthreads, for instance) and then give me the chance to apply the things I just learned. I think most employers care far more about how quickly you can pick up new things than they care about what you already know, and it left me with the feeling that they gave me an offer because of what I can do, rather than what I already know.