Is it a really best practices to raname key word 'type'?

Hmm. Good point. Perhaps ball_type or ballType would have been better. :-/

In general I would not view this solution as best practices because the built-in function "type" is being masked. Am I wrong to think so in this context?

Next time please create a kumite directly on the kata instead, so that the solution is not available for everyone to see.

Alright, but that was just an arbitrary number I put in so that it wouldn't time out. The thing is, no number in the actual test cases was that high.

I think the author somehow screwed with the Hash class to make it unusable for the solution. :/ as in, if you try to use this code for the solution it will just fail, period.

Can you give me an example of a case that it breaks on? I'm reading about loop detection now.

Using a hash will break in certain cases. Try reading about loop detection on wikipedia or stackoverflow for alternative strategies.

This works. The challenge must be broken.

Why won't Hash work?? It works great in all my test cases. I'm using object.object_id to identify them.

What's the 0 for at the end?

In my opinion this is the best solution because it's generic. If the rules of the game change this will still hold with only minor changes. Keeping solutions to already solved problems to avoid crazy recursion complexity scaling is exactly what dynamic programming is. I did pretty much the same thing except by recording recursion answers using the @memorize decorator.

That's really interesting. Can you post your code? It didn't do this to me, so I'll need your code to test it.