Comment by osy

It's true that nobody is expected to balance a binary tree as part of the job but the point of these questions is to see how you approach the problem and how you communicate your solution. Given that you can't perfectly predict how someone will do at the job, employers use leetcode problems as a proxy. Even those who memorize leetcode solutions must also memorize how it works and understand the solution. Given that the problem is random and you're likely given multiple interviews, it's unlikely you've memorized the exact problem and solution without cheating. If you've memorized enough solutions that it's likely you've seen the problem before and you can understand the solution enough to present it, then you're in the 0.1% and deserve to pass.