An answer two years too late, but your code returns the incorrect result when T is unsigned. The vs function is where the problem lies.

Well, this one is ancient, so it might be the reason

But it actually is very annoying that kata's difficulty has a very weak correlation with its actual level of difficulty

Free points, lol

That sould be 7 at best, too easy for lv6.

Too easy to be a 5, this should be 7 at best.

this should be a kata 7 at best, too ez.

std::string already keeps track of its length, that would make sense only for C-Style string.
But thanks anyway.

Assert::That (sortTheInnerContent (input, strlen (input)), Equals (expected));

It looks like it's the length of the input string. Read the posts below, as I don't really do C++ but there are some posts about that already.

what is that int input in c++ version for?

This should be KATA 8, too ez;

Too ez for a 5k KATA, should be ranked as 7.

No clue here either, but maybe you can find something useful in this article: https://docs.codewars.com/training/troubleshooting