Meta Software Developer interview questions

I had two technical interviews (they are not back-to-back, with about a two-week interval) plus one team matching interview on the phone. The whole process took 4~5 weeks. In both tech. interviews, there were two simple algorithm problems. My interviewer shared me a link on collabedit and I just coded there. All questions were quite basic and nothing surprising happened.

I was interviewed by a technical person who is working on my interest area. And after some basic information emails, I was appointmented at a Thursday. They are using some web coding pages, then I joined that chat, the interviewer showed me a problem of coding. That problem was about tree, I didn't have much experience on trees so I asked him to change for some other questions. Finally I got an array question, but I didn't answer it wisely. Thus I got the rejection just the next day, their response time is really short.