Meta Software Developer interview questions

A recruiter has contacted me through linked-in, asked whether I'll be interested to work for them, then had a talk about why would I like to work for them and I replied: that I would like to work with the best engineers. Afterward I had a phone interview with some engineer, asked me to write binary search, when I finished, he asked me to write binary search on a shifted array (10 20 1 2 3 4). Wrote that and then asked me to find the offset (2) in log n. I guess I did that ok and then I was invited to onsite interview. I had 4 consecutive interviews: first one was a general talk about my experience, second was to write a json beautifer, third was to design their newsfeed, and last was to write a program that prints all subsets of size k of a given set with n integers.