As much as people say they don't care about the answer and suboptimal is okay, generally it isn't, there's very often a very specific answer they want you to ar

As much as people say they don't care about the answer and suboptimal is okay, generally it isn't, there's very often a very specific answer they want you to arrive at or you are some version of wrong; so the interview is either failed or succeeds on whether or not the interviewee has seen this problem (or one close enough to be virtually indistinguishable from it) before and can remember how to monkey dance through the steps of it again. Which is ironic, because most (if not nearly all) real-world problems are never solved optimally on the first go -- but rather via a succession of approximations (many of them wrong, and requiring partial or full retreats).