Probably won't - this was never an Issue about it actually being a duplicate.

You addressed the issue about duplicate possible answers, so just let this comment die, and don't worry too much about it.

If someone thinks it should be unpublished, they'll ( have to ) raise a separate Issue.

No biggie. If it is, then it is.
When or how will I know that this kata should be deleted?

You are mistaken, even if you may not be wrong in this instance.

Minor changes are not enough to make a kata not a duplicate. Generally, different encoding of input(s) or output(s) are not sufficient to make a kata not a duplicate. Even if the problem setting is entirely different, tasks may effectively be the same even if they're explained in different terms, because the solutions are practically the same because the underlying concepts are isomorphic.

Being a simpler version may or may not make a kata a duplicate - if the lower requirements make a simpler, totally different, approach possible, it's probably not a duplicate - though then the more difficult kata may spoil the simpller one ( and / or the other way around ). ( Imagine being able to just enumerate a problem somehow vs. having to do something clever. )

If one kata can be solved with a solution from another one ( possibly with minor changes for input / output encoding ), it's very probably a duplicate.

It's not always black and white, and kata are more often duplicates than new authors would like.

Changed the description to ask only for the first longest substring and added a fixed test for that.

About the duplicated kata; I think that even if it is a minor change to return the actual string insted of the size of said string, they presents two different scenarios. And that validates the existence of this one.

Altenatives are:

• Asking the other author to change their kata to ask for the first substring instead of the length and invalidating 300+ answers.
• Not allowing a new kata with a different reason to exists (this one) just because it is similar but not equal.

Don't take me wrong, if I'm mistaken, then thats it. You are the gatekeepers of this place :)

mybad, fixed

I see, the only yellow belt part in this kata is understanding the description.

Because b is not a and c is not b. Then a new a comes and it would be repeating the first one.

Why did the example says abcabcbb expect the result to be abc, when abc is clearly repeating?

Shouldn't it be no non-repeating string in abcabcbb, because each of the characters does repeat.

If the only difference between the two katas is this (one asks the substring, the other the length), it is still a duplicate IMO. The change to make in the code to adapt it to the other kata is absolutely trivial compared with the task itself.

Redesigning for asking length is one possibility; another, as I said below, is asking for the first longest substring.

This requires no redesigning, just some extra testing, and will not allow people to use their solution to the other kata unchanged.

findLongest... ages

ages?

there is a close duplicate to this one (with performance requirements): https://www.codewars.com/kata/5bcd90808f9726d0f6000091

I didn't find another duplicate. This one could be acceptable as an easy version. Though please consider fixing the issue I raised about possible duplicates in answers. The cited kata asks the length of the longest subsequence, it can be a better option (unless you enforce the impossibility have duplicate answers in tests); however it all should be stated clearly in the description.

also might be wise to change it to 6kyu. Will keep an eye for feedback and change it if necessary.

substring made up of unqiue characters? Best I can offer.

Without stricter performance requirements than the current solutions allow, I am not sure if ( something equivalent to ) this has not been done yet.

( With the 5kyu estimate, I actually expected a higher performance requirement. )

If some smart dynamic programming wizardry can solve this kata faster than is necessary here, that might make for a nice performance version of this kata. ( And even that may have been done and I just don't know it. )

For now, not a problem. If somebody recognises this kata as being a duplicate, please link to the original.