链表系列一＞两两交换链表中的结点

题目：

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解析：

代码：

/*** Definition for singly-linked list.* public class ListNode {*     int val;*     ListNode next;*     ListNode() {}*     ListNode(int val) { this.val = val; }*     ListNode(int val, ListNode next) { this.val = val; this.next = next; }* }*/class Solution {public ListNode swapPairs(ListNode head) {if(head == null || head.next == null) return head;ListNode newHead = new ListNode(0);newHead.next = head;ListNode prev = newHead;ListNode cur = prev.next, next = cur.next,Nnext = next.next;while(cur != null && next != null){//交换节点prev.next = next;next.next = cur;cur.next = Nnext;//交换之后继续往后走prev = cur;cur = Nnext;if(cur != null)next = cur.next;if(next != null)Nnext = next.next;}return newHead.next;}
}