LintCode之两两交换链表中的节点

 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 
10 
11 public class Solution {
12     /*
13      * @param head: a ListNode
14      * @return: a ListNode
15      */
16     public ListNode swapPairs(ListNode head) {
17         // write your code here
18         if(head == null) {
19             return null;
20         }
21         if(head.next == null) {
22             return head;
23         }
24         ListNode h = head;
25         ListNode p = head.next;
26         while(p != null) {
27             //交换两个节点的值
28             int temp = head.val;
29             head.val = p.val;
30             p.val = temp;
31             head = p.next;
32             if(head != null) {
33                 p = head.next;
34             }else {
35                 p = null;
36             }
37         }
38         return h;
39     }
40 }