Meta Developer interview questions

I went to my college's career fair and dropped off my resume with Facebook, we had a nice chat. Next week, they sent me an e-mail asking me to come in for a first-round interview on campus. The day before the interview, we had a nice meet and greet in the computer science tea room. They were very friendly, and we got to know each other better. The next day, I had my first interview. It comprised of a few technical questions, and runtime analysis which I think I answered correctly. In the evening, they e-mailed me telling me I've made it to the second (final) round. However, I did not manage to complete the second round challenge within the time limit, and I was not given an offer.