Kata

AFAIK:
"())(()))" the case at hand
"())  (()))" seperated into contained groups
so the second group has a length of 4

I don't know what you mean by "reduces to", but this:

())(()))
   ^^^^ 

is the longest balanced bracket substring. Whereas ()(()) is not even a substring of the given string.

Thanks, I get it now. Boy was I barking up the wrong tree here

Many linear solutions in python 3 can't pass tests if they aren't exactly the same as referee solution.

I don't know what this means. Sometimes, referee solution's result is wrong? Or..

I think he means a solution which runs in linear time still fails .

Thanks @cliffstamp, that's exactly what I mean.

Due to number of tests, difference between execution time and time limit is very tight - at the moment only one set of instructions pass test suite in Python. However I assume purpose of test suite is to assert that player's solution runs in linear time. So lowering number of tests a bit might be wise to not prevent good solutions to pass tests.

Sounds like an issue to me...

Execution speed should be checked with tests which solutions with bad time complexity cannot pass, not by running lots of tests while imposing tight time limits. Unless it's a micro-optimization task, though the description doesn't says so anywhere.

In fact, the description doesn't even mention the performance requirements of the Python version.

It did mention performance requirements for all versions and yes micro-optimization is also an issue in my view but let's hear what myjinxin thinks about it.