I had two back-to-back phone interviews with different engineers, each lasting one hour. They both asked fairly straightforward questions, with moderately more difficult follow-up questions. I applied for a program for freshmen and sophomores in high school, so the questions were tailored to that experience level. Both interviewers were nice and personable, even over the phone.

I don't recall the exact question, but there was one about binary trees and one about recursion.