Apple Software Developer interview questions

Recruiter contacted me for phone interview. Phone screen took 20 min and they flew me over the next week for interviews with 8-10 people.

A friend of mine referred me for a position and was immediately contacted by the recruiter for the team to schedule a phone screen with the hiring manager. This was mostly a technical interview for an hour. I was then invited for a full day on onsite interviews from 11 am to 5.30 pm. The onsite interviewers were all good to talk to and smart obviously. There is a lot of coding on a laptop with the screen projected and also a lot of white board coding and system design. The questions were not extremely tough but makes you think in terms of DS and Algorithms. The lunch turned out to be a very technical interview in itself but now the entire team is shooting questions at you. Overall, it was a good learning experience. My brain was too tired by the end of the day at 5 pm and I got a puzzle question which I was unable to solve which might be why I did not get the offer because most of the other interviews were fine but there may be other factors as well.