leetcode 6 旋转链表

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给定一个链表，旋转链表，将链表每个节点向右移动 k 个位置，其中 k 是非负数。

示例 1:

输入: 1->2->3->4->5->NULL, k = 2
输出: 4->5->1->2->3->NULL
解释:
向右旋转 1 步: 5->1->2->3->4->NULL
向右旋转 2 步: 4->5->1->2->3->NULL

示例 2:

输入: 0->1->2->NULL, k = 4
输出: 2->0->1->NULL
解释:
向右旋转 1 步: 2->0->1->NULL
向右旋转 2 步: 1->2->0->NULL
向右旋转 3 步: 0->1->2->NULL
向右旋转 4 步: 2->0->1->NULL

``` python 3 def rotateRight(self, head: ListNode, k: int) -> ListNode: if not head or k <= 0 or head.next == None: return head

# get length
length = 0
head_ = head
while head_:
    length += 1
    head_ = head_.next

if k % length == 0:
    return head

k %= length

# get mid
head_ = head
step = length - k - 1
while step:
    head_ = head_.next
    step -= 1
# get end
mid = head_
while head_.next:
    head_ = head_.next
# exchange
new_head = mid.next
mid.next = None
head_.next = head
return new_head ```