It's an interesting exercise to write it from scratch. Also, I've specified for this translation in the description and full tests that Data.List.transpose is not imported.

Also, doesn't Scala have transpose in its standard library?

Haskell has transpose in the stdlib. Are you sure this translation is a good idea?

Haskell translation

Approved

C++ Translation

I was so close...

Updated Groovy Translation

Thanks, in polish, J is considered a vowel... :) but it worked now!

Approved

• returned string is not nul-terminated
• if (letter != 'a' || letter != 'e' || ... ) will always be true

j is not a vowel.

I am not sure why my solution is giving a random results - the "passed" test cases is always different each run I do.

Care to explain what should I change?

Is it work for capital Vowel letters..?

The tests are correct. See https://docs.codewars.com/training/troubleshooting