Meta Software Engineer interview questions

The first round was a phone call with HR to schedule the phone technical interview and discuss interests. The phone technical interview is the coding interview with an engineer on Facebook. They use HackerRank for coding environment. The question was easy to medium difficulty with many follow up questions from the engineers.

I passed the first interview, though I think I did not perform well. First 5 minutes self-introduction, and then went into the coding part. The question is easy, but I am too nervous. I took 45 minutes solving only one problem.