well, sorry. Maybe you're not cut out for a life of software development....or maybe you are. Since there is no shortage of differing opinions on the importance of using simple programming puzzles during interviews so it really could go either way.
I think the use of interview puzzles is fine, but I consider those that ask about things like linked lists, recursion, or b-trees to be useless, primarily because they involve what I consider "solved problems" and frankly do not offer much to spark conversation during the interview. Isn't that the point anyhow? Personally I'd rather use either a concrete example of an actual problem that I've faced on one of my projects or instead ask them to solve an unsolvable problem. On the one hand you get to discuss relevant issues using current technology/languages and on the other you get to see how the person thinks through complex problems -- both critical factors in finding the right developer as far as I'm concerned.
Title: When is the interview?
Snarky: x = x + y; y = x - y; x = x - y;