It works. But the question is what you aim for:

• least lines of code
• most robust solution that you can easily reason about
• efficiency in terms of intervals
• efficiency in terms of the total length of intervals

I'm not saying one is definitely better than the other, especially since this is not a code for production, but for practice. For this reason it could also make sense to supply several implementations for each of the above goals.

You have given me hope.

Please use spoiler flag next time.

He creates a list interpreted as queue which already contains the root node. The queue needs a first element otherwise the while loop would not execute its body.

what does [node] expression mean?

just because the kata is too old to have proper performances tests.

But it works

but especially bad about performances...

The best, congratulations!! Very simple and clean!!

This is terrible practice and not clever. The whole point of these helpers is to use the linked list structure to run those methods. If you're converting back into an array why even have a linked list? These solutions are 3x slower than necessary.

ok, now i know

can anybody explain that... its a tricky question to me ...