【LeetCode】Swap Nodes in Pairs

http://oj.leetcode.com/problems/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.

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) {
*         val = x;
*         next = null;
*     }
* }
*/
public class Solution {
public ListNode swapPairs(ListNode head) {
if(head!=null&&head.next!=null){
ListNode cur = head;
while(cur!=null&&cur.next!=null){
int temp = cur.val;
cur.val=cur.next.val;
cur.next.val=temp;
cur=cur.next.next;
}
return head;
}
return head;

}
}