The details say: 'Note: do NOT mutate the nodes!'

But screw dem rules! Limitations are for pussies, right? =)

I like this one =)

Clever one =)

Iterating from the end... Yep, that's clever)

Clever indeed!
However, debugging this solution would be a pain. For instance, if there is no odd number in the array, the result would be 0; the same result as if we had an odd 0 in the array. If there were multiple odd numbers, the result would be unpredictable as well.
The input should always be correct. Thus, the solution is great for a coding playground, but will definitely bite you if you use it in a real project.