数组和链表的算法题

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# https://leetcode.cn/problems/swap-nodes-in-pairs/

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def swapPairs(self, head: ListNode) -> ListNode:
        p, p.next = self, head
        while p.next and p.next.next:
            a, b = p.next, p.next.next
            p.next, b.next, a.next = b, a, b.next
            p = a
        return self.next