链表_leetcode24

# Definition for singly-linked list.
class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution(object):
    def swapPairs(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """

        dummyHead = ListNode(0)
        dummyHead.next = head
        p = dummyHead


        while  p.next and p.next.next:

            node1 = p.next
            node2 = node1.next
            next = node2.next

            p.next = node2
            node2.next = node1
            node1.next = next

            p = node1

        return dummyHead.next