[LeetCode]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.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
	public ListNode rotateRight(ListNode head, int n) {
		if(head==null) return head;
		ListNode ln = head;
		ListNode last = null;
		ListNode res = null;
		int len = 0;
		while (ln.next != null) {
			ln = ln.next;
			len++;
		}
		len++;
		int k = len-(n%(len));
		if(k==0||k==len) return head;
		ListNode ln2 = head;
		int seq = 0;
		while (ln2.next != null) {
			seq++;
			if (seq == k){
			    last = ln2;
			    break;
			}
			ln2=ln2.next;
		}
		ln.next = head;
		res=last.next;
		last.next=null;
		return res;
	}
}