The interview consisted of two phone interviews, each an hour in length. After getting past these, I was flown to Mountain View for a six-hour interview that consisted of five, one-hour interviews with different people and one hour for lunch. The phone screens were scheduled about two weeks apart, and each was very technical. The onsite interview focused on programming problems, with one of the interviewers asking me questions about my experience. All the people I met with were very nice.

Write a function to validate a binary search tree.

Find the common numbers in two text files.