leedcode 旋转链表

将链表的首尾相连，然后新链表的头结点，断开即可

 

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def rotateRight(self, head: ListNode, k: int) -> ListNode:
        if head is None or head.next is None:
            return head
        cur = head
        n = 1
        while cur.next:
            cur = cur.next
            n = n + 1
        cur.next = head
        count = n - k % n
        while count > 0:
            cur = cur.next
            count = count - 1
        newNode = cur.next
        cur.next = None
        return newNode