题解 | #奶牛排队#

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param head ListNode类 
# @return ListNode类
#
class Solution:
    def reorderCows(self , head: ListNode) -> ListNode:
        # write code here
        if not head or not head.next:
            return head

        tail = head
        current = head
        next_node = current.next

        if next_node:
            while next_node.next:
                current = next_node
                while current.next.next:
                    current = current.next
                tail_next = current.next
                current.next = None
                tail.next = tail_next
                tail_next.next = next_node
                tail = next_node
                next_node = next_node.next
                if not next_node:
                    break

        return head