Solution.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null || head.next == null) {
            return head;
        }
        int n = 0;
        ListNode cur = head;
        while (cur != null) {
            ++n;
            cur = cur.next;
        }
        k %= n;
        if (k == 0) {
            return head;
        }
        ListNode p = head, q = head;
        for (int i = 0; i < k; ++i) {
            q = q.next;
        }
        while (q.next != null) {
            p = p.next;
            q = q.next;
        }
        ListNode start = p.next;
        p.next = null;
        q.next = head;
        return start;
    }
}