This basically gives the answer ...

Issue resolved. Thanks.

You log too much in user feedback on error:

Max Buffer Size Reached (1.5 MiB)

Thanks a lot for the tip. Number theory is not something I knew anything about. I would have been stuck for a long time!

Not a kata suggestion, but a useful one ~~

Any solution which is not O(1) will timeout depending on the input size. While approving this I was not sure what to do with that limit, since author had just 1 fixed solution of size 690. Now, I've updated the description to have bound of 690.

I mean that with O(n^3) complexity, it will time out in some cases. You can try out this input I constructed:'A'*(250-1)+'X'+'B'*(250-1)+'X'*250+'A'+'Y'*250 . I'm sorry, but your solution actually times out.

That was the required time complexity.

This problem has n<=1000, but most solutions, including the Sensei's, actually has O(n^3) time complexity, and can be hacked by this input: match('A'*(250-1)+'X'+'B'*(250-1)+'X'*250+'A'+'Y'*250)

Ok I kinda solved the kata, so now I have access to the solutions, and I agree with you that ice1000's solution is quite unreadable =P I'll try to make sense of it tomorrow.
EDIT: aaand I give up.

What on earth is this?!

I'm not bothered by it; just clarifying the intended purpose of the tags.

Oops, clicked reply twice, just egnore this one

Thanks for telling me that, I'm new to here, hope that didn't bother you :)

Suggestion tags are for suggestions on changes to the kata. If you just want to provide a suggestion on an approach to solving the challenge, there's no need for the tag.