A recruiter contacted me via Facebook message as well as my email. On the first call, the recruiter explained the interview process and the different divisions of Facebook I could work for. A first telephonic interview was set up. I wasn't prepared for the interview, so, as I expected, I didn't do well.

Given a binary tree, write serializable and deserializable methods for it:

java public LinkedList serialize(Node root); public Node deserialize(LinkedList list);

Write possible test cases for this.

What is the most challenging thing that you worked on in Android?

How to persist data between sessions in Android.