Was contacted by facebook recruiter. I thought I will give it a try. I selected in person tech screen vs phone interview since I think it is much easier to express yourself in person, plus there is whiteboard. Especially, if it is a graph or tree problem, easier to draw on whiteboard. I had to sign NDA unfortunately, so won't be able to share the exact question. But for a software engineer (not senior), the question was pretty hard to solve in 40 minutes. Backtracking was required and the best solution to the problem is n! (n factorial). So if you haven't heard of the problem before, it is quite likely you will spend time just on finding an optimal solution before jumping to code. That's what I did. However, I was able to code most of the solution and interviewer seemed happy. He himself told me that. Interviewer was pretty nice. He answered my questions pretty well and seemed down to earth, only thing I am not sure is the choice of question. I was informed that they will not move ahead with the on-site round, which is what I expected.