how is mine?

It's not the most optimal though. With larger inputs, the difference will start to become noticeable. You should totally avoid iterating twice.

The array is either entirely comprised of odd integers or entirely comprised of even integers except for a single integer N

How did I not think of that?! It's so easy!

i basically did the same but long way but i think is not the best with O(2n) why is this top in the first place becuase is short or what ?

Do you need to handle errors? Like if the array has no outliers or more than 1? Or the array is smaller than 3?

going over the "very large array" twice ends up taking twice as long, twice as much memory.
if the array was billions of members long - the 10 lines of code you saved would cost a lost of money.

this code may be impressive to newbies exclusively.

definitely not best practice, you use var, not strict equality operator and filter array twice

This solution is at least 8 years old.

stop using var please, is missleading

Thanks, I just started reading Groking algorithms to be more competent

There is no such thing as 'O(2n)' in big O notation. There are different notations which keeps the constant multiplier before function, such as 'tilde notation', see https://www.reddit.com/r/compsci/comments/1bl0q8/tilde_notation/. But you are right this solution is quite inefficient.

Lol, author says that array can be VERY big, and O(2n) solution gots top place when O(1) solution takes hardly more time to come with)

I'm not saying mine is better, jsut asking a question mate, i'm here to learn.