[Leetcode] Swap Nodes in Pairs

Given a linked list, swap every two adjacent nodes and return its head.

For example,
Given 1->2->3->4, you should return the list as 2->1->4->3.

Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.

 

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) {
 7  *         val = x;
 8  *         next = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13     public ListNode swapPairs(ListNode head) {
14          ListNode dummy=new ListNode(0);
15         dummy.next=head;
16         ListNode cur=dummy;
17         while(cur.next!=null&&cur.next.next!=null){
18             ListNode nextNode=cur.next.next;
19             cur.next.next=nextNode.next;
20             nextNode.next=cur.next;
21             cur.next=nextNode;
22             cur=cur.next.next;
23         }
24         return dummy.next;
25     }
26 }

 

posted @ 2014-10-21 01:13  Phoebe815  阅读(102)  评论(0)    收藏  举报