First round: 2 back-to-back skype interview, 1 hour each. I was asked to design an elevator system. Then questions about checking unival trees, and count unival subtrees. The interviewers were very helpful. Did not come up with the best answers on the first tries, but got them right with hints from interviewers. Second round: 30 minutes phone interview with a manager. Discussed design of a project I did. Got offer on the next day.