AppDynamics Software Engineer interview questions

I applied to this company through on campus career fair. On the next day of the career fair, I got a on campus interview. That one is quite simple (two-pointer Linkedlist style question). I got a phone interview from that. However, the phone interview didn't go well...The interviewer spent twenty minutes asking about logistics questions of Java, followed by a difficult coding question, a top view binary tree kind question. He didn't explain this problem well.