Leetcode Odd Even Linked List

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.

The program should run in O(1) space complexity and O(nodes) time complexity.

Example:

Given 1->2->3->4->5->NULL,
return 1->3->5->2->4->NULL.

 class Solution(object):
     def oddEvenList(self, head):
         """
         :type head: ListNode
         :rtype: ListNode
         """
         if head == None or head.next == None:
             return head

         dummy = odd = head
         connectNode = even = head.next

         while even and odd:
             t = even.next
             if t == None:
                 break

             odd.next = odd.next.next
             # or odd.next = even.next
             odd = odd.next

             even.next = even.next.next
             # or even.next = odd.next
             even = even.next

         odd.next = connectNode

         return dummy