Given a singly linked list, and a number "n", find the nth element from end in the Linked List
Note that this is a sinigly linked list and you cannot traverse in the backward direction.
given linked list: 1 -> 2 -> 3 -> 4 | nthFromEnd (2)
output: 3
given linked list: 1 -> 2 -> 3 -> 4 | nthFromEnf (5)
output: undefined
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