The description should be clarified.

It should read something like:
The array is either entirely comprised of odd integers and a single even integer or entirely comprised of even integers and a single odd integer.

Currently it reads:
"The array is either entirely comprised of odd integers or entirely comprised of even integers except for a single integer N."

If one reads that "or" as exclusive, it means that the only time there will be an outlier to return is in the case of the array containing mostly even integers.