I think I don't get what should be the pattern for the grandchild.
If child has to get 1 or 2 diffrences that mean grandichild should get from 0 (because they could cancel out) to 4. Is my logic correct ?

I was going in a similar direction but your is way cleaner.

I see. I will be more humble in the future.
Thank you for your comment.

I saw other guy who wrote code in JS and had the same issue.
I think the number of loops declare in a test is just to big for JS to handle and that is the issue.
My function is quite simple so I don't any doubts.

I added my code in comment above with spoiler warnning. I would be happy if you prove me wrong.

That is a realy amazing solution. I saw in a earlier comment that you did it in a hurry.
I am interested how many years take to became so good at this?