Is it better to use stringstream to concatenate strings than regular += operator?

I agree with you that there are upvoated solutions by "coolness", but I'll suggest a different solution.

The Clean Code category is already covered by the Best Practices. The problem is the lack of a regular
Like button that everyone seems used to.

People just want to express that they've liked a solution, regardless of its practices or cleverness.
I think Codewars should give that option, so the other categories can remain "unpolluted" by those votes.

I've seen wrong solutions being accepted. I think this final test case should be added: '(this))is((invalid)'

Hi! Be careful, your solution says that '(this))is((invalid)' is valid.

Good job. Fast tip: your final if and returns could be just return r == 0

Hey, be cool, you're in the beautiful land of Python. It's not C :)