A recruiter contacted me through LinkedIn approximately a week before the phone interview (45 minutes).

If you move forward, you proceed to onsite interviews. For my experience, FB was very quick to set everything up for me; I heard back about not moving to onsite the day after my phone screen.

It seems that FB values not only the optimal solution for questions but also the ability to be quick on your feet to identify and implement the optimal solution swiftly.

While I did arrive at the optimal solution (the question is on LeetCode), I struggled with an edge case for about 15 minutes before the interviewer guided me to rectify it. However, the interviewer was pleasant to talk to.

The first 5 minutes were spent discussing what I was working on at my internship and what my interviewer's team does. The next 35 minutes were dedicated to the one coding question, and the rest of the time was spent asking more questions.

In hindsight, I felt I should have given myself more time to prepare.

Given a number of size less than or equal to 999 billion, return its string representation (for 123, return "One Hundred Twenty Three," not "123").