题目链接:https://leetcode-cn.com/problems/swap-nodes-in-pairs/
题目如下:
思路:
/** * 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) { //tip: //1、当整个操作过程中,头节点会发生变动时,可增加一个虚拟节点 //2、操作中三个指针普遍适用 //3、链表按着顺序来,从后往前,确保不会出错 //4、链表题要画图 if(head==null||head.next==null) return head;//链表中元素仅有0或1个 ListNode dummyhead=new ListNode(0); dummyhead.next=head; ListNode p=dummyhead; while(p.next!=null&&p.next.next!=null){ ListNode node1=p.next;//链表节点数>=2个 ListNode node2=p.next.next; System.out.println(node1.val); node1.next=node2.next; node2.next=node1; p.next=node2; //dummyhead->node1->node2 before //dummyhead->node2->node1 after p=node1; } return dummyhead.next; } }