Facebook Interview February

Current Status: Working at A10 Networks as Software Engineer, Application Security
Summary of Rounds: After initial phone call with the recruiter, there were three telephonic rounds. Normally they conduct two phone screen, but I presented my interest in Security role, hence one extra round!
Telephonic Round 1: 45 minutes programming: Reverse a string in place. Modification 1, Reverse it without reversing words, Modification 2, Remove all trailing spaces in front or extra spaces in between a string, and a tuple (reversed string, length).
Telephonic Round 2: 45 minutes programming: Find closest time permuting digits of a given time in hh:mm. Modification 1, Without repeating any digit.
Telephonic Round 3: 45 minutes Security discussion. Write a bash script to identify correct phone numbers. Can be in usual formats, (ddd) ddd-dddd or dddddddddd or ddd-ddd-dddd. Modification 1, Phone numbers can have country codes.
1: Maths problem. System design for large input calculator.
2: Pour x ml liquid into two distinict glasses with y and z ml capacity. Modification 1, you can empty the glass to half. Question asked, how can I do that (logical).
3: Datastructure questions, sorting algorithms and quick coding.
4: Lunch, behavioral questions.
5: Networking questions, MPLS, BGP, Source-sync questions on graphs.

Experience: Interviews were quite straight forward, and people are very polite. Enjoyed the process.