12. Quiz N

(similarEnds) An array has similar N-ends if the front and back N numbers are either in the reversed order.

Return the largest N value for which an array has the same N-ends.

• N is a positive integer.
• Give -1 if the ends are not similar at all.

Examples:

1. similarEnds([20,30,40]) => -1.
2. similarEnds([20,30,4,5,30,20]) => 2.
3. similarEnds([20,30,40,50,50,40,30,20]) => 8. The repeating segments overlap.
4. similarEnds([10,20,30,20,10]) => 5.