Your code fails for case below when they are same number-pairs that sum together to the same total. Specifically, your logic in checkIfExistsInArray is wrong

that's the joke (hence the ":)")

That's not "clean", that's just way more code than necessary.

This solution is better than best one. No magic numbers

!

?.

I can't see this error. Can you post your solution so we can try to reproduce it?

I've added the picture that describes adjacent cells better.

I think it is described good enough, could you be more concrete about details should be added?

I agree, in an interview type situation you can't look up the value of a character. Cleaner, even though there is a '+1' in there because of it.