1. Get contacted by a recruiter via email (I was already on their database due to a prior application).
2. Set up call with HR person (initial recruiter was actually very nice, and solved all my doubts).
3. Had phone interview.
4. Received an email where I'm invited onsite and that a different person will manage onsite details.
5. Suddenly, the recruiter who'd manage my onsite interview stopped responding to emails; I haven't heard from this person in over a month now. No explanations were given.

Question about trees and pre-order traversal.