Yes, you're right, I don't know why I did it)

Yes, I agree with you. And your solution is very accurate

Amazing Kata!

WTF?? ))

Ok, but why? )

Really good solution!

I see this is the right test:

tailAndHead([1,2,3,4,5]) should return 945

Perhaps you forgot to correct the description? )

I completed the first two katas.

But this does not change my question.

Does anyone know why the very first example needs to return 1939 instead of 19391??

Yes, right, for me tags are part of the description )

Why is #Array listed in the description?

Maybe it needs to be removed?

RileyHunter, thank you for the explanation!

I was confused, when I saw that reduce actually repeated four times. But now, I understand why this solution is better than mine!

Can you explain to me, why this works so fast?
What value will Big O take?

The third parameter of the function is not needed, the solution can be more compact, if you want, you can look at my solution

Several people have the same solution, is this possible? ))