[johnamata]

I also had that problem, I grinded through 200+ problems but I felt like I was just memorising leetcode solutions. I dont wanna be a shill but if you can pay, then check out a site called structy.net, it's a hidden gem. Nevertheless you dont need to pay as 50% of its content is free. Compared to famous paid interview prep resources like algoexpert, it's way cheaper, explanations are more succinct, and personally I find it explains things better.

I worked through it and I'm confident I can smash leetcode mediums, especially trees and graphs. Arrays and Strings I found to be the hardest at leetcode hard level as there are a ton more corner cases to handle and there's almost no problem solving patterns in solving many of them, unless it's the "easy-hard" type (usually backtracking types like Sudoku Solver are manageable). Most leetcode hard array problems are just pure manipulation and observational/ad hoc types and it's hard to get good at them as there's little practice available in leetcode to ease you to such problems. One has to go to sites like codeforces to practice these ad hoc types, and it's annoying as codeforces problems are mathy. Luckily, those hard array problems dont appear in leetcode style interviews.

Anyhow, structy and the "top interview questions" from https://leetcode.com/explore/interview/ were enough for me to go from "forgot everything from algorithms class" to interview ready.