zoukankan      html  css  js  c++  java
  • 24. 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.

    关于链表的题, 画图看看需要那几个节点, 一般都是接头节点(用作标记) 和遍历节点, 遍历的时候要判空, head.next !=  null 前一定要判head != null, 

    将尾节点置为空!

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode(int x) { val = x; }
     * }
     */
    class Solution {
        public ListNode swapPairs(ListNode head) {
            if (head == null || head.next == null) {
                return head;
            }
            ListNode dummy =  new ListNode(0);
            ListNode pre = dummy;
            while (head != null && head.next != null) {
                ListNode temp = head.next.next;
                pre.next = head.next;
                pre = pre.next;
                pre.next = head;
                pre = pre.next;
                head = temp;
            }
            if (head != null) {
                pre.next = head;
                pre.next.next = null;
            } else {
                 pre.next = null;
            }
           
            return dummy.next;
            
        }
    }
    

      

  • 相关阅读:
    metasploitable实践
    免杀技术
    SQL注入
    ARP欺骗
    使用Nmap攻击靶机和使用Wireshark进行嗅探、分析
    Nmap
    搭建网络攻防环境
    20139216网络攻防技术第七次作业
    Android代码实现求和运算
    命令行输入参数,并实现排序
  • 原文地址:https://www.cnblogs.com/apanda009/p/7396782.html
Copyright © 2011-2022 走看看