of course works

I tested it, it worked for sure:

    public static void main(String[] args) {
        String str = "hellllllloooo";
        System.out.println(clever(str));
        String str1 = "hi";
        System.out.println(clever(str1));
        String str2 = "";
        System.out.println(clever(str2));

    }
 
 #########oooo
hi


    

do not retreat and do not give up

We all get there at some point, and you have to admit that for a 7 Kyu this was quite tricky in practice

3 days is a bit long ;)

where are you from? your nickname seems familiar.

Test case 5 in Java is not about empty arrays. It's about nulls. Do you check for null in your code?

You can use the equality operator (==) with the null keyword. So, if (a == null) { do things differently }

((a.length == 0) & (b.length == 0)) : It depends on language, but if this is exactly how you have it in code, then it's most probably wrong.