Given a linked list, swap every two adjacent nodes and return its head.
Example:
Given1->2->3->4, you should return the list as2->1->4->3.
Note:
迭代，记得画个图，不然会懵逼
class Solution { public ListNode swapPairs(ListNode head) { ListNode dummy = new ListNode(-1), pre = dummy; dummy.next = head; while (pre.next !=null && pre.next.next!=null) { ListNode t = pre.next.next; pre.next.next = t.next; t.next = pre.next; pre.next = t; pre = t.next; } return dummy.next; } }
原文：https://www.cnblogs.com/wentiliangkaihua/p/10337287.html