题目
Given a linked list, swap every two adjacent nodes and return its head.
You may not modify the values in the list’s nodes. Only nodes itself may be changed.
解题思路
创建一个dummy节点指向头，之后的结点两两交换
代码
class Solution:
def swapPairs(self, head: ListNode) -> ListNode:
dummy = ListNode(0)
res = dummy
dummy.next = head
while dummy.next and dummy.next.next:
first = dummy.next
second = dummy.next.next
first.next = second.next
second.next = first
dummy.next = second
dummy = dummy.next.next
return res.next
