First round interview at the Facebook Seattle office. The question was related to string parsing: basically given a set of key value pairs in some format, to print them according to another format. I did not understand the specifications clearly and probably should have spent more time doing that. Instead, I went through many iterations with the interviewer pointing out specific mistakes each time. My advice: the question may be very different from what you think it probably is, so spend enough time making sure you get it. Also, in case of this problem, it was algorithmically very simple, but you are bound to miss some cases and make certain mistakes. So, when you see a simple problem, try to look at the problem and your solution carefully for possible gotchas.

String parsing.