Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

Solution:
It is possible that K > num of nodes.
First try: connect all nodes:1->2->3->4->5->1->2->3->4->5.... complicated.
Second try: notice that after rotating (num of nodes) times, the list would be the same. (point!!!!!) 
So K = K mod (num of nodes). 

public class Solution {
    public ListNode rotateRight(ListNode head, int n) {
        // count the number of nodes in the list
        int count = 0;
        ListNode node = head;
        while(node != null){
            count++;
            node = node.next;
        }
        
        if(count == 0) 
            return null;
        n = n % count;
        
        ListNode slow = head;
        ListNode fast = head;
        
        // fast is n steps ahead
        while(n > 0){
            n--;
            fast = fast.next;
        }
        
        while(fast.next != null){
            slow = slow.next;
            fast = fast.next;
        }
        
        fast.next = head;
        ListNode nt = slow.next;
        slow.next = null;
        return nt;
    }
}