Amazon Software Developer interview questions

I was contacted by an Amazon recruiter via LinkedIn. I interviewed with them previously (unsuccessfully) and looks like they had me in their database. The recruiter told me that they have a hiring event in LA and if I am interested, I can try. Of course I was interested. I have been obsessed with this job for a very long time. I failed once, but I learned a lot since. I decided to give it a try. The event was in three days. Sure, I read up on some algorithms, but there is not much one can do in this kind of time. What I knew would have to be enough for success or failure. They interviewed people in the hotel in LA. You get a separate room, and interviewers walk in, and each one of them gets about 45-50 minutes with you. They ask some theoretical questions (for example, design some classes for a chat system) and some whiteboard coding. As to the coding, there was a lot of recursion and binary trees. There was nothing extremely hard or undoable, no NP-hard problems I was afraid of. I had 4 technical interviews and one talk with the recruiter. The interviewers were great - friendly and pleasant. I got through without glaring errors or missed questions. But I feared that I was not brilliant enough for them. I was right.