What are the hardest leetcode problems?

If you know the question number off the top of your head of a question that you think is the hardest, you are preparing for interviews wrong and cramming Leetcode way too hard. Unless you want to be in programming competitions and aren't trying to get hired. If you learn the right techniques for how to approach problems, and have practiced the fundamental techniques, no problem should be hard. The only exception is problems that solely rely on an obscure computer science algorithm that isn't used anywhere else except for this problem, but you shouldn't be studying those on Leetcode, except for fun.

I worked with someone today who spent the vast majority of the past week, only studying graph problems for one of the hardest companies to get into and they weren't asked any graph problems and we're only asked string problems. You are missing the point in that you still need to learn graphs, dynamic programming strategies and much more complex approaches to solving problems. But people have attendancy of sitting in their room cranking through these problems alone and thinking they know how to do them when in fact they've just really memorized or convince themselves they understand them without really getting signal from the outside that they do until the interviews. An engineer needs to learn how to solve problems in general. You are paid the big bucks to solve new problems not to regurgitate hard solutions from Leetcode. I'm my opinion you are going to have a stressful and hard time otherwise and have a lower probability of passing I helped grow Facebook from 200 engineers to 10,000 engineers, did hundreds of interviewers, helped create an interview type, helped train interviewers, so I'm just giving my advice from my perspective, you can always do you and do what you want to prepare and whatever works for you!

Feel free to DM if you want some broader career advice from my perspective, you seem frustrated at your job hunt right now. I don't really know what to say but you sound like you went down a rabbit hole. I assure you many people at Facebook were denied offers if they cranked out answers way too quickly and could not demonstrate how they solved the problem, even if they knew how to solve it in their minds. So you sound like you have a lot of the energy and dedication and raw smarts to do well at these companies, but you're a little tunnel vision on the approach. You should revisit this post in 3 years and reflect on it.

Me personally, I can't compete in any interview requiring understanding of specific algorithms at that level. If you are preparing for these companies you need to prepare for all of these topics as the TABLESTAKES, and then you need to also learn how to interview well using those skills. If you fail to do that, you won't pass no matter how much you know.

All the billionaires I'm friends with aren't on Reddit calling people losers, but you do you.