That's what happens when your code segfaults on Codewars

There is no need for caching...

Did you read a post below:

So it turned out in my case above, the error was the result of a failing test, but it appears the test harness doesn't know how to handle std::pair<>, hence the 'unsupported type' message. Once I fixed the bug in my code, the 'unsupported type' errors went away.

I don't know why but the C++ Unit tests returns "Unsupported type" when your test fails.
Print the input and your results and you will see that they are wrong hence the "unsupported type". Your solution doesn't pass the first fixed test. Sorry but I am not the C++ Unit tests writer:-(