I got a paper containing code of a c function. The interviewers left the room for 5-10 minutes so I can study the code, then returned and asked questions about the code.

I have arrived 20 minutes perior to the scheduled time. Went to the office floor as instructed and all I found was an empty floor with keycard entry only. no option to talk with someone to let me in. the recruiter also was not available over the phone. So I found my self standing there, with no toilet access, for about 30 minutes (10 minutes into the interview time). I was then finally been able to reach the recruiter HR phone and she sent the interviewers to open the door for me. in the interview itself, they explained about the company in general, and regarding the job itself. afterwards, they wanted to hear my background and knowledge.