leecode24

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| 字数统计 69 | 阅读时长 1

题目

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class Solution:
    def swapPairs(self, head: ListNode) -> ListNode:
        
        newhead = ListNode(0)
        
        newhead.next = head
        
        l1 = newhead
        if l1.next is None:
            return head
        l2 = newhead.next.next
        if l2 is None:
            return head
        while True:
            tmp = l1.next
            l1.next = l2
            tmp.next = l2.next
            l2.next = tmp
            l1 = tmp
            if l1.next is None:
                break
            l2 = l1.next.next
            try:
                l2.next
            except:
                break
        
        return newhead.next