I consider myself a proficient developer, however, in situations where I'm required to solve an obscure puzzle while someone is staring at me, generally makes me uncomfortable...no matter how easy the question. I interviewed for an internship position at Microsoft, where I was required to write some bizarre code on graph paper while the interviewer literally stood over my shoulder. Horribly uncomfortable, I barely made any progress, and was subsequently denied a position (obviously). After the interview, I went home and solved the question in a matter of minutes, wrote the code, optimized, and fully tested it. While I choked during the interview, I saw fellow classmates fly off to Redmond...classmates that I knew weren't better developers than I was, simply because I had worked with many of them on projects several times. That's when I knew this whole puzzle interview stuff was nonsense.