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.

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[code]

public class Solution {
    public ListNode rotateRight(ListNode head, int n) {
        if(head==null || head.next==null || n==0)return head;
        ListNode p=head;
        int len=1;
        while(p.next!=null)
        {
            p=p.next;
            len++;
        }
        n=n%len;
        p.next=head;
        ListNode q=head,tail=p;
        p=head;
        for(int i=0;i<n;i++)q=q.next;
        while(q!=tail)
        {
            p=p.next;
            q=q.next;
        }
        head=p.next;
        p.next=null;
        return head;
    }
}