Who said it wasnt useful, dont listen to those people.

People who are applying to jobs and are tested with LeetCode problems to assess their skill level, despite the two not really being correlated or relevant for the position

As someone that gets very annoyed when having to do LeetCode in interviews...

Knowing algorithms, data structures and their memory and time complexities is very relevant for SWE. I've had teammates that didn't understand them and everything was fine until when it wasn't (scaling and performance issues).

Or, as I put it to a teammate: "Would you rather review the PR of someone that understands the difference between a set and a list or the PR of someone who doesn't?". This was after we interviewed a candidate with ~15 YoE, on paper, that didn't know the difference.

> Knowing algorithms, data structures and their memory and time complexities is very relevant for SWE

Agree with this; however knowing how to roll your own BFS/LRU/etc isn't -- in that case I'd rather review the PR of someone who understands how to leverage tested and known implementations than the PR of someone who decided to roll their own.

Who care's if the leetcode question doesn't relate to the job itself, it shows whether or not the person is willing to put in the work and gives you a glimpse into their ability to reason about hard problems.