A linked list is a fundamental data structure. Being expected to reason about fundamental data structures is not unreasonable.
Unless you specifically know that taking 20m to reverse a linked list was the reason for not being hired (I'm skeptical), you're just guessing.
While I don't generally ask questions like this, I'd also be wary of someone that can't reverse a linked list in 20 minutes, although it depends on what type of position you're actually applying for.
I also didn't go to a competitive school; I don't know what arbitrary criteria you'd use to decide if I've "done anything special".
I expect coders to be able to code, or at least reason about code, more or less on demand. I'm pretty forgiving about poor whiteboard coding performance since I also suck at it. But even a terrible whiteboard performance can be accompanied by the thought process behind it, and from that, you can discern whether or not the coder knows anything and just sucks at being put on the spot, or if they truly don't know.
Unless you specifically know that taking 20m to reverse a linked list was the reason for not being hired (I'm skeptical), you're just guessing.
While I don't generally ask questions like this, I'd also be wary of someone that can't reverse a linked list in 20 minutes, although it depends on what type of position you're actually applying for.
I also didn't go to a competitive school; I don't know what arbitrary criteria you'd use to decide if I've "done anything special".
I expect coders to be able to code, or at least reason about code, more or less on demand. I'm pretty forgiving about poor whiteboard coding performance since I also suck at it. But even a terrible whiteboard performance can be accompanied by the thought process behind it, and from that, you can discern whether or not the coder knows anything and just sucks at being put on the spot, or if they truly don't know.