LeetCode - Swap Nodes in Pairs - Frequent

https://leetcode.com/problems/swap-nodes-in-pairs/

这种题都可以用dummy node来解决，不过要注意其中node指针换来换去的细节问题，很容易错。

代码如下：

public class Solution {    public ListNode swapPairs(ListNode head) {        if(head==null || head.next == null) return head;                ListNode dummy = new ListNode(0);        ListNode traverse = dummy;                while(head!=null && head.next!=null){            ListNode tmp = head.next.next;            traverse.next = head.next;            head.next.next = head;            traverse = head;            head = tmp;        }        traverse.next = head;        return dummy.next;    }}