[Lintcode]Swap Nodes in Pairs

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

Example

Given 

1->2->3->4

, you
should return the list as 

2->1->4->3

.

简单的实现题。按照描述写代码即可。

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
/**
* @param head a ListNode
* @return a ListNode
*/
public ListNode swapPairs(ListNode head) {
if(head == null) return null;
ListNode dummy = new ListNode(0);
dummy.next = head;
ListNode prev = dummy;
while(prev.next != null && prev.next.next != null) {
ListNode cur = prev.next;
ListNode tmp = prev.next.next.next;
prev.next = prev.next.next;
prev.next.next = cur;
cur.next = tmp;
prev = prev.next.next;
}
return dummy.next;
}
}