[neild]

Perhaps I've just worked with linked lists too much at this point, but I find it nigh impossible to understand how reversing one could be considered even minimally difficult. "Pop the head of the source list and prepend it to the target until the source list is empty." One sentence, no complex concepts involved at all.

If it's unfair to expect someone to answer a question like that in an interview, then I'm not certain what is fair. In a world where people with literally no programming skills whatsoever regularly apply for programming jobs, I need to apply some filter to weed out the incompetent. Sad experience has told me that educational credentials and claims of past work experience are insufficient.

[barrkel]

It's very hard for you or I now, to appreciate what it was like before you learned to think of linked lists as stacks. The point is, there is definitely a leap of insight necessary if you've never thought of things in this way before. I was 12 or so when I made the leap, and I guess I'm slightly lucky that I remember the exact moment for this particular case.

[kenjackson]

I don't think I knew what a linked list was at age 12, but I don't think you even have to know what a stack is to do this. Just draw it on a whiteboard, and it becomes obvious that you just walk the list and flip arrows. Seeing that linked lists can represent interesting structures is I think an even more advanced concept, but one that is unnecessary for this particular question.