Don't like such examples. Why you creating additional collection? We can do it without it.
People, don't like such examples. We are learning algorithms, not modern languate SHUGAR!!!

Codewars is also here to showcase actual best practices and this is one of the rare cases where the votes match.

Horrible and slow solution.

worst solution. this is codewars, you should write your own logic and not use existing solution

Actually, it really may not compile due to project style violation rule like 'do not use single char names outside of lambdas'
(see lint)

So in a java project,this code won't compile?

This code for C programming lang. For JAVA u should write high level code. It's unreadable for real project.