链接：24. 两两交换链表中的节点 - 力扣（LeetCode）

直接写

 1 # Definition for singly-linked list.
 2 # class ListNode(object):
 3 #     def __init__(self, val=0, next=None):
 4 #         self.val = val
 5 #         self.next = next
 6 class Solution(object):
 7     def swapPairs(self, head):
 8         """
 9         :type head: Optional[ListNode]
10         :rtype: Optional[ListNode]
11         """
12         if head == None or head.next ==None:
13             return head
14         lNode = head
15         rNode = head.next
16         resNode = rNode
17         llNode = lNode
18         while lNode and rNode:
19             llNode = lNode
20             lNode.next = rNode.next
21             rNode.next= lNode
22             lNode = lNode.next
23             if lNode and lNode.next:
24                 rNode = lNode.next
25                 lNode.next = rNode
26                 llNode.next = rNode
27             else:
28                 rNode = None
29         return resNode
30