Meta Software Engineer interview questions

Interview consisted of a phone interview and then an all-day on-site interview with four one hour interviews. I was really impressed by the difficulty of the questions that they asked and the level of thinking and coding they expected. After the interview, I wasn't sure if I would be happy working at facebook so they let me come back and speak with me would-be manager and director as well as some coworkers so I could make a good decision.

A Facebook HR recruiter contacts me directly through Facebook saying if I am interested in interview. The process consists of a phone interview and an onsite interview. Phone interview is asking my background and experience, while onsite interview is 30 minutes intense real coding question on white board. Two questions were given in the onsite interview. 1st one is reversing a linked list, and the 2nd one is writing a regular expression parser. However, since it only allowed 30 minutes to write actual codes for both questions, I wasn't able to finish them. (I finished 1 and 2nd one is half way) I then never got the reply from them.