数据结构算法操作试题(C++/Python)——两两交换链表中的节点

class Solution(object):
    def swapPairs(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        tmp_head = pre_head = ListNode(0)
        pre_head.next = head
        while tmp_head.next and tmp_head.next.next:
            next2_p = tmp_head.next.next.next
            tmp_head.next.next.next =  tmp_head.next
            tmp_head.next = tmp_head.next.next
            tmp_head.next.next.next = next2_p
            tmp_head = tmp_head.next.next
        return pre_head.next