Meta Software Engineer interview questions

A recruiter contacted me. After a few days of back and forth we set up a phone interview. In the phone interview we discussed a possible problem that involved trees. I struggled to implement the necessary algorithm. Eventually, I got to ask a couple of questions about facebook. Received a decline a couple weeks later.

I applied through website took 2+ months. FB is very efficient in hiring. The HR first sent some regular questions for me to answer, including the time to start working and so on, and then arranged the phone interview directly. On the same day of my phone interview, she arranged for onsite interviews. I was impressed with how efficient they are.