[skybrian]

If the interview is irritated they're not doing it right. In my case I'd just ask the interviewee to explain his or her answer, and if it holds up, make sure to write in the report to the hiring committee that nobody else I interviewed came up with this answer before. That's why it's an interview and not a standardized test.

Coming up with an unusual solution should be a win, though it's of course not required.

Also, in some cases I might ask a slightly harder follow-up where the shortcut doesn't work.