':type head: ListNode
:rtype: ListNode'

def oddEvenList(self, head):

    if head:
        (odd_tail, cur) = (head, head.next)
        while (cur and cur.next):
            even_head = odd_tail.next
            odd_tail.next = cur.next
            odd_tail = odd_tail.next
            cur.next = odd_tail.next
            odd_tail.next = even_head
            cur = cur.next
    return head
