Stories like yours and the grandparent comment give the impression that there is little communication actually happening in an interview. I guess if it was an at home assignment given in an email you might not know what the interviewer wanted, but in an actual in-person interview why wouldn't you just say "Well, you could do String.reverse(), is that what you're looking for[?], or would you like me to implement a solution without using String.reverse() or some other way?"

And on the other side, if the interviewers are looking to identify whether a candidate knows about String.reverse() and the candidate starts writing out some 20 line algorithm on the whiteboard, why would you just sit there and watch instead of being like "actually, we're looking for something else, let me ask it a different way; do you know how to reverse a list using the standard library? We're looking for a one-liner here, not an full algorithm implemented on the board."

If your story is true, then apparently there are at least some interviewers willing to just sit there while a candidate writes out 2 completely different algorithms on a whiteboard without interrupting and communicating what they actually want. Such an interviewer is either socially incompetent or trying to make a fool out of the candidate. Either way it doesn't reflect well on the company.

Yes, you would think. But for some reason, a lot of interviewers seem to treat interviews as an opportunity for them to prove that they're superior to the person that they're interviewing.

Yup. If I get even the slightest inkling of this attitude from the interviewers, I will refuse to join the company. I'll give a pass for one smug interviewer, but if I encounter multiple such interviewers, I assume it's not a company I'd like to work at.

That or they have already made up their mind and are just looking for an excuse to reject the candidate.

When I was interviewing for my current job I was asked to theoretically sort a list with with N elements where N >> M where M is the total number of bytes in RAM (but with infinite disk). I thought ok, easy, I basically explained every step of MergeSort except instead of doing operations in the memory, we need to some operations in the memory (i.e. merging) and then need to dump middle products to disk. You need to be a little more clever since you can't just merge in memory and save in disk (e.g. you can't perform the very last step of merging two N/2 N/2 arrays in memory since N/2>>RAM). Anyway, I was confident with my answer, and my interviewer sounded happy too. Then he asked me "but why don't you use swap?" Hmm I was very surprised. Since this wasn't a coding question (I was already asked dozens of questions involved programming) I thought this was a purely theoretical question. So, I never thought about the systems aspect. On a second glance, it indeed seemed like I just reinvented swapping.

I think CS interview questions can be hard because sometimes you don't know what sort of "model of computation" are you operating on. Am I on a totally abstract setting where all I have is an abstract machine. Or do I literally have an Intel CPU running Linux? Or am I even higher level than that and can think in terms of the abstraction of python. I think sometimes this is not clarified.

One other time in a different interview, I was asked "how does OS free memory in constant time". Having implemented malloc etc a few times I thought this was a stupid question because it depends on the C library implementation of malloc/free as one could also implement free in O(logn) using tree-like structures. Anyway, said something like "it just clears the pointer in the linked list in sbrk()'d space so that node is inaccessible" which apparently was the "correct" answer.

>"Or am I even higher level than that and can think in terms of the abstraction of python. I think sometimes this is not clarified." //

Which may be the point, they want you to ask "what am I optimising for", to be aware that there's no simple best answer without needing prompting. Also that the optimisation might be at the business level, like time critical implementation, or use of excess resources gleaned from some other part of the corporation.

So instead of telling you they want a one-liner, you saying "what are our constraints; how long have I got to implement it, ...".

Well, that is very informative, but probably not in the way the interviewer intended. Certainly doesn't sound like a great place to work?