24. 两两交换链表中的节点.ipynb

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    "# Definition for singly-linked list.\n",
    "class ListNode:\n",
    "    def __init__(self, x):\n",
    "        self.val = x\n",
    "        self.next = None\n",
    "\n",
    "class Solution:\n",
    "    def swapPairs(self, head: ListNode) -> ListNode:\n",
    "        flag = True\n",
    "        my_list = ListNode(None)\n",
    "        my_list.next = head\n",
    "        point = my_list\n",
    "        while head:\n",
    "            if flag and head.next:\n",
    "                point.next = head.next\n",
    "                point = point.next\n",
    "                head.next = point.next\n",
    "                point.next = head\n",
    "                flag = False\n",
    "            elif not flag and head.next:\n",
    "                head = head.next\n",
    "                point = point.next\n",
    "                flag = True\n",
    "            else:\n",
    "                break\n",
    "        return my_list.next\n",
    "\n",
    "def printNode(head):\n",
    "    while head:\n",
    "        print(head.val)\n",
    "        head = head.next\n",
    "    \n",
    "a = ListNode(1)\n",
    "s = Solution()\n",
    "printNode(s.swapPairs(a))             "
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