1. /**
    2.  * @Description 一遍过了，可以奥
    3.  * @Date 2022/1/19 11:09 下午
    4.  * @Author wuqichuan@zuoyebang.com
    5.  **/
    6. public class Solution {
    7.     public ListNode swapPairs(ListNode head) {
    8.         ListNode dummyHead = new ListNode();
    9.         dummyHead.next = head;
    10.         ListNode pre = dummyHead;
    11.         while (pre.next != null && pre.next.next != null) {
    12.             ListNode node1 = pre.next;
    13.             ListNode node2 = pre.next.next;
    14.             ListNode node2Next =  node2.next;
    15.             node1.next = node2Next;
    16.             pre.next = node2;
    17.             node2.next = node1;
    18.             pre = node1;
    19.         }
    20.         return dummyHead.next;
    21.     }
    22. }