I'm baffled by how some of these people can answer all 4 questions in 30 minutes. It takes me at least 10 minutes just to read and understand the first/easiest question, let alone correctly solving all 4 of them. Seems fishy. I don't believe anyone who is truly unfamiliar with the problem can solve it that fast. They must have seen the problem in one way, shape, or form. They may be very good at mapping new problems onto older, known problems, and that's definitely a skill if that's what they're doing. Or perhaps they are polymaths or Ph. D graduates with a much deeper study of algorithm design than I received with my Masters degree. I'm a smart person with a solid education, but I never received in depth training on how to design these very complex algorithms in such a short period of time.

Any employer who is expecting a Bachelor or Masters-level educated person to be able to scratch out something like "Number of Music Playlists" on a whiteboard in a few minutes during an impromptu interview session is being unrealistic. They are looking to pay someone at a Bachelor/Masters level, but they're looking to hire someone at a PhD/Post-Doctoral level.