24. 两两交换链表中的节点-LeetCode

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) { val = x; }
 7  * }
 8  */
 9 class Solution {
10  public ListNode swapPairs(ListNode head) {
11           if(head==null)
12               return null;
13            ListNode rHead=new ListNode(-1); 
14            rHead.next=head;  ///不要忘记赋值。。。。。
15            ListNode tmpHead=rHead;
16            ListNode tmpNode=rHead.next;
17            while(tmpNode!=null&&tmpNode.next!=null)
18            {
19           tmpHead.next=tmpNode.next;
20           tmpNode.next=tmpHead.next.next;
21           tmpHead.next.next=tmpNode;
22           tmpHead=tmpNode;
23           tmpNode=tmpHead.next;
24            }
25            return rHead.next;
26         }
27 }