Where are you interviewing where this is the case? So I can never apply there. This is definitely not what we do, and if you interview with me and you give me mechanical answers you're out the door. This is for a fairly large multinational, interviewing for a technical software job. In the technical interviews I'll usually give problems that are borderline unsolvable. There's usually a trick to solve it really efficiently, but if you come up with just the trick and nothing else you're not getting hired. I want to see you get it wrong. I want to see you get it wrong a dozen times, and learn why it's wrong, and try to think your way out of the pit you've dug again and again and again. I want to see you get creative, use tricks of the architecture to solve theoretical problems, and come up with half a dozen different kinds of approaches. I want you to see why each one is brilliant or stupid, what's good about it, what's bad about it, and try again and again and again. People who show up expecting the usual canned standard answers usually look sort of like a deer in the headlights and are back out the door in 15 minutes.
Doing things this way works. I know this because most of the really brilliant people I've worked with have done fantastic in this situation. I don't want to hear the right answer because there is no right answer. The more you can show me about how you think about a problem and how sneaky you can get, the better you do.