The interview process involved three phone interviews.

The first two were technical interviews with various members of the team. The third interview was more HR-oriented with minimal technical questions. The offer was extended after the third interview.

Conducting the interviews over the phone was a little awkward, especially when I had to write a C++ implementation of Breadth-First Search and read my solution line by line. There was also an instance where my interviewer missed my second interview, and we had to reschedule.

All in all, though, these things happen, and I felt the interviews were effective at testing my knowledge. They were also pretty prompt about getting back to me.

I wouldn't say there was a most difficult question. There were numerous data structure and algorithm questions involving linked lists, hash tables, and operations on binary representations. There were also questions about operating systems. I remember virtual memory and paging came up more than once.