题解 | 两两交换链表中的结点

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
#
# @param head ListNode类
# @return ListNode类
#
class Solution:
    def swapPairs(self, head: ListNode) -> ListNode:
        # write code here
        a0 = ListNode(0)
        # x0为指针
        a0.next, x0 = head, a0
        while x0.next and x0.next.next:
            a1, a2 = x0.next, x0.next.next
            x0.next = a2
            a1.next = a2.next
            a2.next = a1
            x0 = a1
        return a0.next