I dont think its O(n^2) because there is only ever 2 numbers in this problem. so I think its maximum O(2n) and minimum O(n).

ah yes! - all numbers are the same so array as input is wrong - my bad :-)

in which all of them are the same, except for one single number.

bad performance -> n**2

it is not right. for array like this:
arr =[]
n = 10000
for x in range(n):
arr.append(1)
arr.append(2)
arr.append(4)
-- after for finished add 1 unique in the middle
arr.append(3)

it returns 4
but is should return 3

Welp, that's too bad. And the author is active too so let's leave it to him. Anyway, you can approve my other translations (or my kata) XD

Dunno it's a mess there's used to be Crystal and JS but author deleted the languages so I'm refrained from approving your JS XDD

To be fair, he did check. He forked some of them. In fact, one of the translation is his own.

JavaScript translation kumited :). Feel free to check

Wait, I'm confused. What's the original language of this kata? There are Python, Java, Ruby, and CoffeSript translations, but these are also the only available languages. You can't translate it to the same language, right?

should be fixed

should be fixed

All fixed, changed description to replace last part with in string format

Dear author, you should check on pending translations before approving them, especially when they had been abondened for years !!!

In Python at least.