How to find nth element from the end of a singly linked list?

Question

The following function is trying to find the nth to last element of a singly linked list.

For example:

If the elements are

Answer 1

Nobody here noticed that Jonathan's version will throw a NullPinterException if the n is larger that the length of LinkedList. Here is my version:

public Node nth(int n){
        if(head == null || n < 1) return null;

        Node n1 = head;
        Node n2 = head;
        for(int i = 1; i < n; i++){
            if(n1.next == null) return null; 
            n1 = n1.next;
        }

        while (n1.next != null){
            n1 = n1.next;
            n2 = n2.next;
        }
        return n2;
}

I just make little change here: when node n1 step forward, instead of checking if n1 is null, I check weather n1.next is null, or else in while loop n1.next will throw a NullPinterException.