[kstenerud]

Yes, it's only a linked list, and reversing it is trivial. The problem comes with the inevitable "OK, now how would you make it more space/time efficient?" question. I've had it countless times, and it's always infuriating because the answer is out there, on google, written by some PHD ages ago. The interviewer himself has read it, which is why he knows, and yet now he expects me to come up with something comparable in a "clean room" situation, usually involving a white board.

Really, those kinds of questions such as algorithm optimization only test your ability to come up with creative solutions in a stressful and time constrained situation. And even then you're not testing that because even the best of us will experience temporary brain paralysis in stressful situations, so you're actually just testing for luck.

And if that's what the working environment is like, fine so long as the candidate knows it's always like that and accepts those conditions (I wouldn't). But if that's NOT what the working environment is like, why are you even testing for it?

[sago]

Really? Reversing a linked list? It really doesn't take a PhD to do that in O(N) time and O(1) space. I don't remember 'reading' an algorithm, isn't it just obvious that you walk through the list flipping the direction of the links?

Now of course, I'm making a specific point about a specific question. I'm not making a point about all 'algorithm whiteboard' interviews. Maybe you misunderstood the point, and thought I was. But I agree, many of them are utterly bonkers. Nobody is going to intuitively derive Floyd Warshall's algorithm with a whiteboard in 10 minutes. And coding trivia interviews are always pointless. If you can learn the right answers to 'pass' my interview, I'm not doing a very good job, imho.

But for very simple things like basic manipulation of the the simplest possible data structure involving a reference, I absolutely think a minimally competent programmer should be able to demonstrate their ability. Can you reverse it? Can you rotate it? Can you split it into buckets? Can you twizzle pairs? Can you insert in the middle? If you can't do those things with a cons-cell, in O(N), I can't imagine how you would cope with basic manipulations on more complex data.