I interviewed with facebook recently for a software engineer position. The initial conversations and recruiter screening went nice and the telephonic interview was setup for a week later. Have documented the experience below:

I overprepared and got nervous before the interview, as it was a big deal for me. The interview started and it felt like time was flying , also the interviewer seemed to be in a rush. I was asked 2 simple similar questions initially for which i gave the optimum O(n) solution with space trade-off. I did check with the interviewer for the space trade-off and he said that's not an issue, I could had still suggested him a better algorithm with O(1) space complexity and mentioned if I should, but he said it's okay we can move to the next question.

The next question was a follow up from the previous question and the space tradeoff was useful here to avoid extra computation and still arrive at an O(n) answer. The time was almost about to be over and I was only able to give him a psuedo code.

I thought I did well and was waiting for my feedback. I recieved my feedback in a couple of days and found out that I was rejected for the following reasons:

1. The name I chose for my extra storage wasnt good enough and one couldnt understand what it was meant for. To those of you wondering, the name of the function asked to be implemented was foobar, hence the name of the variable i chose was fooArr.

2. The other reason that was mentioned was that I gave the solution with suboptimal storage.

Now , if i come to think of it, I did ask him if i should give the other solution, but the interviewer himself said we could move on to the next question. Also, in a 45 minute interview where you solve 2-3 problems for 35-40 mins, with explaining the solution to the interviewer , writing proper code and testing if it works, should a candidate be rejected because they did not use the right variable name? This is not the first bizzare rejection reply I recieved but certainly I felt disappointed and bad because the opportuntiy and role meant a lot to me, given I have been laid off right now and have been preparing hard for my interviews.

It feels bad to finally get a call for FAANG companies and then get rejected for something that sounds so trivial. Has anyone ever faced similar experiences before and how do you cope with constant rejection in such times?

PS: I have also interviewed with Amazon and got rejected there because I suggested a O(n) time complexity for a solution which was actually O(KN) solution, the k was really small for the problem that was asked , i did mention it that it should be technically O(kn) but given the problem(not test case) at hand k was 3 I gave the final answer as O(n). [The recruiter told me I got the time complexity wrong and hence was rejected].

PPS: As software developers/recruiters do you think it is okay for companies to reject candidates in preliminary rounds for getting the time complexity/variable name wrong, when the recruiters keep mentioning throughout the process that we are evaluating your thought process, so think out loud?
Doesnt my expeience actually suggest me to just work quickly and hard for the best solution and code it out rather than spend time on explaining small details and thinking out loud?