Meta Software Engineering interview questions

I got email from the recruiter shortly after my friend in Facebook referred me. The recruiter asked me a few basic questions in the phone and arranged a phone interview. The phone interview took about 1 hour and the interviewer asked two questions. Shortly after that they told me to have an on-site interview in their campus. The on-site interview is 1-on-1 and the interviewer asked me two questions that is of average difficulty. But it is very important to communicate your solution clearly to the interviewer. Then within one week, I got the internship offer from Facebook.

One of my friends refers me. Then, I appeared one screening interviews. Interviews with algorithm, data structure. No behaviour question. No additional question, just coding. After coding, will ask you how to improve the performance, or do you have another way to implement it.