@natan I'm not sure how it would be, other that my comment was a bit vauge. Getting that exception means null is present and the user has attempted an action on null that's not allowed. So, they have to track that down. Knowing that the parameter is an array narrows the search... well, it's tuens out it's the input, hence the unexpected exception. I already knew the 4th test had null. In any case, the OP has solved it, possibly from my hinting, I suppose. (FYI the exception did not provide a line number)

@rowcased I feel like that's a bit misleading considering the arguments involved here. not sure if you've looked at test4 for C# but I know I'd be confused by what you wrote

@BrandoL keep in mind that you can print from within your solution. also consider carefully the error message and maybe you have a line number/location for it as well which might tell you a lot about what's happening. reading the instructions may also help since this situation is mentioned there.

the error message is telling you something.

• a null exception has occured.
• the value cannot be null.
• the parameter is an array

ergo

• an array cannot be null