[LeetCode] Rotate List

Problem:

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:O(n)

public class Solution {
   public ListNode rotateRight(ListNode head, int n) {
      if(head == null || n==0 || head.next == null)
         return head;

      ListNode slow = head;
      ListNode fast = head;
      for(int i=0; i<n;i++){
         fast = fast.next;
            if(fast == null)
               fast = head;
      }
      if(fast == slow)
         return head;
      while(fast.next!=null){
         fast = fast.next;
         slow = slow.next;
      }
      ListNode ret = slow.next;
      slow.next = null;
      fast.next = head;
      return ret;
   }
}