61. 旋转链表

public class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if(head == null|| k == 0) {
            return head;
        }
        int size = 1;
        ListNode tail = head;
        while (tail.next != null) {
            size++;
            tail = tail.next;
        }
        k = k % size;
        ListNode prev = head;
        for(int i = 0;i < size - k - 1; i++){
            prev = prev.next;
        }
        tail.next = head;
        head = prev.next;
        prev.next = null;
        return head;
    }
}