Not to get meta on you, but you're assuming that I'm assuming. I assure you I'm not assuming anything. I tried it myself, successfully, having never done it before, and it's not that hard to solve. Someone else posted their solution here. Good programmers can come up with that kind of code routinely, mediocre programmers can't. And this is a test to distinguish the classes.

Talking about software design methodology cannot tell me whether someone can write new algorithms correctly. If I have a job that requires people to correctly design algorithms, I think asking questions about algorithm design is entirely appropriate.