Meta Software Developer interview questions

The interview process was very smooth. The recruiter kept me in the loop.

This was for a position in their Infrastructure team in Cambridge MA. Recruiter contacted me in September and was very interested in my background and experience with highly scalable systems - both in Finance and Mobile phone payments. I attended some small intimate presentations they did as they were initially opening a new Boston office and wanted to grow it out. The meetings were great and I learned a lot about how they solve some of their biggest problems. I then did a screening interview on-site (because I don't do technical screens well on the phone). The question was "Given a binary tree, write code to print the tree out line by line". I did OK and got the Breadth First Search down fine, but couldn't figure out the - line-by-line part. (Turns out this is Facebook's #1 question to ask in interviews). Although my performance wasn't great they gave me a break on that and asked me back for another screening interview. This time I prepared well for another coding interview but it turned out to be a Design interview. The problem was "Imagine you have 10,000 servers and need to monitor the performance of each one, how would you do it" - naturally you need to be able to NOT take too much of the bandwidth and so you'll have to do sampling, have some history to watch for trends etc. I passed that and was very excited to be flown out to Menlo Park for the final round. I studied like CRAZY based on questions on this site and CareerCup. I took 4 weeks and studied about 15 hours per week. Turns out I focused on the wrong questions - I studied Tree, String, Array and List algorithms based on the distribution of Q&A but I was asked Binary math and heap algorithms. Here are the questions I was asked. 1) How would you implement division without +, - or multiplication (a "classic" question, but not one of the ones I would focus on). I bombed on this as I was not expecting and could not recall my binary math. I figured out the high level outline but that was all. That I was asked this in the "culture fit" interview made this doubly unexpected. 2) Given 10,000 servers containing a Billion integers each how would you find how to find the median? I knew the answer to this question (use two heaps) - not because I had focused on it, but I had found it an interesting question while studying. However he then asked "How much memory do you need?" and I didn't know how big the heaps would need to be. The real answer I was trying to get is - what is the minimum heap you need. I had a guess but I think I got this wrong. 3) Given a List structure where each node contains a Next node and optionally a pointer to another list, flatten that list e.g. L1 --> L2 --> L3 --> L7 --> L8 | v L4 --> L5-->L6 WIll be flattened to L1 --> L2 --> L3 -->L4 -->L5-->L6-->L7-->L8 I did OK on this - getting the answer - but it appeared I took too long. The interviewer also interrupted me a lot while I was writing an initial solution and that threw me off - I like to be more iterative in my problem solving but I think he expected 100% immediate correctness. He had an observer there too and that guy looked bored out of his mind and that bugged me a little too as it wasn't clear who would be doing the judging. 4) I was also handed some hard to read Python code (I don't know Python) and asked to figure out what it does. I did OK on this - but again surprised to be handed hard-to-read code in a language I didn't know. 5) One final question "How would you implement the "ls" Unix function in your language of choice. It should take the input: >ls a/b/c/*/e/*/f/*/*/g and the output should be similar the the output given by unix." I used a tree structure to represent the file directory structure and wrote a solution from there. I did OK on this. Overall: Everyone seemed very nice - I had a nice lunch and the campus is interesting but it was clear that what I studied was not what I needed to (so lesson learned: don't just trust the distribution of questions on Glassdoor or CareerCup). I even got to walk past Zuckerberg's office (more of a conference room) and saw Sheryl Sandberg in there. One interesting thing I learned is a lot of Google people are leaving for Facebook. Also I'd say if you are over 30 (I am 41) you are a rare bird at Facebook :-) I knew based on the reactions of the interviewers that it was very probably a bust, but overall a good experience and something I will learn from. Very disappointing as I really wanted to be one of the first few Facebook engineers in the Boston area - and to work on their super high scalability issues but such is Life.