I was first contacted by a recruiter at Facebook. She told me that my background was very impressive and asked if I would be interested in a software engineer position. I said that I would be excited, and she scheduled the next round of interviews with a Facebook engineer. It wasn't an on-site interview but a phone screening right before it.

The engineer first asked me why I would want to work at Facebook. Then we moved on to two technical questions.

1. Merging two sorted arrays (both length n) in the most efficient way when the latter of the arrays has a buffer size of 2n.
2. Writing a function that checks if a tree is a binary search tree.

For the second question, I had the right idea of using in-order traversal to check if it was a binary search tree, but I couldn't finish the implementation on time. After the interview, I wrote it in an editor myself and was sad to find out that it was not that complex at all.

Anyway, I am still waiting for a reply and I hope I can proceed to an on-site interview. :)