It's so amusing how interviewers pose questions that took PhD students years to invent the answers to. Just say you want me to memorize some algorithms and their time+space complexities, and regurgitate them on command.
> It's so amusing how interviewers pose questions that took PhD students years to invent the answers to.
That doesn't really mean anything without additional context... like what the questions you're talking about were, or what the positions were, or what you claimed about your background, approximately how long ago said PhDs were earned, or what the interviewers actually expected from you (which may not have been the final solution at all), or... etc.
So much of what we learn, use, and understand was developed by people far more talented than us. Literally everything from algebra to binary digital logic. It should be obvious that something can be orders of magnitude more difficult to come up with the first time, when you have nobody to learn it from, and when the rest of the world is far behind where the field is, than it might be to come up with it when the entire world has advanced and you've (presumably) been taught extremely relevant material & perspective in a nice and polished classroom setting. Now, obviously, it can also be just as difficult in the second case as in the first case for some problems too. It depends entirely on the problem and context.
Some do. Other companies expect you to derive the algorithm from scratch if you haven't seen that one. If you don't know the algorithm, then question is over. It's unreasonable to expect someone to derive in 10 minutes something that took years to invent.
That’s not what I’m looking for in those kinds of interviews. For example, one of my fav problems has a Range Sum Query tree idea as the main solution. But I’m more than happy to lead any developer to the solution, they come away happy with new knowledge, I see how they respond to hints and think on a new problem. Always fun and heard a lot of direct thanks for that from interviewees.