I was contacted by an HR representative who was very kind. She provided enough material to prepare for the entire interview process, starting with the phone screen.

The phone interview lasted exactly 45 minutes.

The interviewer called me. He started with a brief introduction about himself and then asked about my background. I took around 3 minutes to give a brief overview of my experience, and I felt he was least interested in hearing it. I could tell because he seemed to be trying to stop me to jump to the coding questions. He didn't even comment on my experience, which made it feel as if he was just following a protocol to get the interview done.

He asked me the first question, and I was able to solve it in 20 minutes with an optimal solution. However, there was no comment from him on whether it was okay or not. He also didn't ask me for the runtime complexity of the solution, which was O(n).

He then just jumped to another question. I used the remaining time trying to get to the proper solution, but I believe I was in the right direction because I researched that question after the interview.

A couple of days later, I received a phone call from HR saying the feedback was not positive. The interviewer felt my coding solutions were not optimal. I was shocked to hear this. Firstly, I solved 1 out of 2 questions properly, and I didn't hear any feedback from him while I solved the problem during the interview. If he thought it was not optimal, what made him jump to the second question? He didn't even ask me about the complexity, or at least he could have said, 'There can be a much better solution; can you think further?' There was no feedback at all.

Based on my research and the videos I've seen, I suspect Facebook interviewers try to see your approach even if it's not an optimal solution.

In the end, he said, 'I only have time for 1 question to answer if you have any, or else I will be kicked out of this room.' These were his exact words.

I was like, 'Really?' Does a company like Facebook not have enough meeting/interview rooms, or do they reserve the room for exactly 45 minutes when an interview is scheduled? I never felt comfortable during this interview; I felt I was rushed.

I couldn't do much when I got the call from HR, but I expressed my side of the story to her.

A message containing letters from A-Z is encoded to numbers using the following mapping:

'A' -> 1 'B' -> 2 ... 'Z' -> 26

Given an encoded message containing digits, determine the total number of ways to decode it.

For example: Given encoded message "12", it could be decoded as "AB" (1 2) or "L" (12).

Given an array of integers, return true if there are contiguous numbers that add up to a specific target.

For example: [6,1,2,3,3,7] target sum is 8, will return true because 2,3,3 adds up to 8 and are contiguous. [6,1,2,4,3,3,7] will return false as there are no contiguous elements that add up to 8.