文章目录

• 节点定义
• 链表类
• • 获取链表长度
  • 清空链表
  • 添加节点到链表尾部
  • 根据id来删除节点
  • 根据id来查询节点
  • 修改相同id的节点信息
  • 打印链表
  • 逆序打印
  • 反转链表
• 测试
• • 代码
  • 打印信息
• 习题
• • 反转链表
  • 删除链表的节点
  • 删除链表的倒数第k个节点

节点定义

关于节点里面所存储的信息，需要什么就添加什么，但是next字段是必须的，因为用来串联一个节点和下一个节点。

package com.dam.data_structure.linked_list;public class HeroNode {/*** 这三个字段自己定义*/public int id;public String name;public String nickname;/*** 必要字段*/public HeroNode next;public HeroNode(int id, String name, String nickname) {this.id = id;this.name = name;this.nickname = nickname;}@Overridepublic String toString() {return "HeroNode [id=" + id + ", name=" + name + ", nickname=" + nickname + "]";}public HeroNode next(int id, String name, String nickname) {next = new HeroNode(id, name, nickname);return next;}}

常规添加节点方法，这样很多小伙伴可能会觉得比较麻烦

HeroSingleLinkedList linkedList = new HeroSingleLinkedList();HeroNode hero1 = new HeroNode(1, "宋江", "及时雨");HeroNode hero2 = new HeroNode(2, "卢俊义", "玉麒麟");HeroNode hero3 = new HeroNode(3, "吴用", "智多星");HeroNode hero4 = new HeroNode(4, "林冲", "豹子头");linkedList.add(hero1);linkedList.add(hero4);linkedList.add(hero2);linkedList.add(hero3);

这里提供一个快速添加节点的方法

 public HeroNode next(int id, String name, String nickname) {next = new HeroNode(id, name, nickname);return next;}

使用方式

HeroSingleLinkedList linkedList = new HeroSingleLinkedList();链式添加元素linkedList.head.next(5, "小明", "小明").next(6, "小花", "小花").next(7, "小华", "小华").next(8, "李华", "李华");

链表类

本文的链表会使用一个空的结点来作为head，该节点上面没有什么实际数据，只是为了让链表的其他方法更加容易实现

public class HeroSingleLinkedList {/*** 先初始化一个头节点, 头节点不要动, 不存放具体的数据*/private HeroNode head = new HeroNode(0, "", "");
}

获取链表长度

注意，计算长度是从head的下一个节点开始计算

    /*** 获取链表长度** @return*/public int size() {int size = 0;HeroNode temp = this.head.next;while (temp != null) {size++;temp = temp.next;}return size;}

清空链表

直接重置头节点就行

  /*** 清空链表*/public void clear() {this.head.next = null;}

添加节点到链表尾部

找到链表的最后一个节点，将最后一个节点的next指向要添加的节点即可

  /*** 添加元素** @param heroNode*/public void add(HeroNode heroNode) {HeroNode temp = this.head;找到最后一个元素，将heroNode添加即可，最后一个元素的next肯定为nullwhile (temp != null) {if (temp.next == null) {//--if--找到了最后一个元素 添加元素之后即可退出temp.next = heroNode;break;} else {//--if--不是最后一个元素，继续往下面寻找temp = temp.next;}}}

根据id来删除节点

删除节点一般是遍历到要删除节点的前一个元素，然后将前一个元素的next指向null或者要删除元素的下一个节点

   /*** 根据id来删除节点** @param id*/public HeroNode deleteById(int id) {HeroNode temp = this.head;while (temp != null && temp.next != null) {if (temp.next.id == id) {//记录要删除的元素HeroNode record = temp.next;if (temp.next.next != null) {//--if--如果还有下下个节点temp.next = temp.next.next;} else {//--if--如果没有下下节点，直接赋值为空就行temp.next = null;}return record;}temp = temp.next;}System.out.println("没有找到相应id的元素，无需删除");return null;}

根据id来查询节点

   /*** 根据id来查询节点** @param id*/public HeroNode getById(int id) {HeroNode temp = this.head;while (temp != null) {if (temp.id == id) {return temp;}temp = temp.next;}System.out.println("没有找到相应id的元素");return null;}

修改相同id的节点信息

    /*** 根据id匹配来修改节点** @param heroNode*/public void update(HeroNode heroNode) {HeroNode temp = this.head;while (temp != null) {if (temp.id == heroNode.id) {temp.name = heroNode.name;temp.nickname = heroNode.nickname;return;}temp = temp.next;}System.out.println("没有找到相应id的元素，无法修改");}

打印链表

   /*** 打印链表的元素*/public void print() {//不打印头节点，从头节点的后一个元素开始HeroNode temp = this.head.next;while (temp != null) {System.out.println(temp.toString());temp = temp.next;}}

逆序打印

利用栈先进后出特性来协助

  /*** 逆序打印*/public void reversePrint() {//先将所有元素存储到栈中Stack stack = new Stack<>();HeroNode temp = this.head.next;while (temp != null) {stack.push(temp);temp = temp.next;}//从栈中取出元素并打印while (!stack.isEmpty()) {System.out.println(stack.pop().toString());}}

反转链表

反转链表原理

 /*** 原地反转链表** @param linkedList*/public static void reverseList(HeroSingleLinkedList linkedList) {HeroNode head = linkedList.head;//如果只有一个元素或者没有元素，直接退出即可if (head == null || head.next == null) {return;}HeroNode cur = head.next;HeroNode last = null;while (cur != null) {HeroNode temp = cur.next;cur.next = last;last = cur;cur = temp;}head.next = last;}

测试

代码

package com.dam.data_structure.linked_list;import java.util.Stack;public class HeroSingleLinkedList {/*** 先初始化一个头节点, 头节点不要动, 不存放具体的数据*/private HeroNode head = new HeroNode(0, "", "");/*** 添加元素** @param heroNode*/public void add(HeroNode heroNode) {HeroNode temp = this.head;找到最后一个元素，将heroNode添加即可，最后一个元素的next肯定为nullwhile (temp != null) {if (temp.next == null) {//--if--找到了最后一个元素 添加元素之后即可退出temp.next = heroNode;break;} else {//--if--不是最后一个元素，继续往下面寻找temp = temp.next;}}}/*** 根据id来删除节点** @param id*/public HeroNode deleteById(int id) {HeroNode temp = this.head;while (temp != null && temp.next != null) {if (temp.next.id == id) {//记录要删除的元素HeroNode record = temp.next;if (temp.next.next != null) {//--if--如果还有下下个节点temp.next = temp.next.next;} else {//--if--如果没有下下节点，直接赋值为空就行temp.next = null;}return record;}temp = temp.next;}System.out.println("没有找到相应id的元素，无需删除");return null;}/*** 根据id来查询节点** @param id*/public HeroNode getById(int id) {HeroNode temp = this.head;while (temp != null) {if (temp.id == id) {return temp;}temp = temp.next;}System.out.println("没有找到相应id的元素");return null;}/*** 根据id匹配来修改节点** @param heroNode*/public void update(HeroNode heroNode) {HeroNode temp = this.head;while (temp != null) {if (temp.id == heroNode.id) {temp.name = heroNode.name;temp.nickname = heroNode.nickname;return;}temp = temp.next;}System.out.println("没有找到相应id的元素，无法修改");}/*** 获取链表长度** @return*/public int size() {int size = 0;HeroNode temp = this.head.next;while (temp != null) {size++;temp = temp.next;}return size;}/*** 清空链表*/public void clear() {this.head.next = null;}/*** 打印链表的元素*/public void print() {//不打印头节点，从头节点的后一个元素开始HeroNode temp = this.head.next;while (temp != null) {System.out.println(temp.toString());temp = temp.next;}}/*** 逆序打印*/public void reversePrint() {//先将所有元素存储到栈中Stack stack = new Stack<>();HeroNode temp = this.head.next;while (temp != null) {stack.push(temp);temp = temp.next;}//从栈中取出元素并打印while (!stack.isEmpty()) {System.out.println(stack.pop().toString());}}/*** 原地反转链表** @param linkedList*/public static void reverseList(HeroSingleLinkedList linkedList) {HeroNode head = linkedList.head;//如果只有一个元素或者没有元素，直接退出即可if (head == null || head.next == null) {return;}HeroNode cur = head.next;HeroNode last = null;while (cur != null) {HeroNode temp = cur.next;cur.next = last;last = cur;cur = temp;}head.next = last;}public static void main(String[] args) {HeroSingleLinkedList linkedList = new HeroSingleLinkedList();链式添加元素linkedList.head.next(5, "小明", "小明").next(6, "小花", "小花").next(7, "小华", "小华").next(8, "李华", "李华");插入测试HeroNode hero1 = new HeroNode(1, "宋江", "及时雨");HeroNode hero2 = new HeroNode(2, "卢俊义", "玉麒麟");HeroNode hero3 = new HeroNode(3, "吴用", "智多星");HeroNode hero4 = new HeroNode(4, "林冲", "豹子头");linkedList.add(hero1);linkedList.add(hero4);linkedList.add(hero2);linkedList.add(hero3);正序打印测试System.out.println("正序打印测试---------------------------------------------------------------------------------------");linkedList.print();System.out.println();逆序打印测试System.out.println("逆序打印测试---------------------------------------------------------------------------------------");linkedList.reversePrint();System.out.println();获取链表长度测试System.out.println("获取链表长度测试---------------------------------------------------------------------------------------");System.out.println("链表长度：" + linkedList.size());System.out.println();反转链表System.out.println("反转链表测试---------------------------------------------------------------------------------------");HeroSingleLinkedList.reverseList(linkedList);linkedList.print();System.out.println();修改元素System.out.println("修改链表元素测试---------------------------------------------------------------------------------------");linkedList.update(new HeroNode(4, "武松", "行者"));linkedList.print();System.out.println();根据id查询元素System.out.println("根据id查询元素---------------------------------------------------------------------------------------");System.out.println("linkedList.getById(2):" + linkedList.getById(2));System.out.println();删除元素System.out.println("删除链表元素测试---------------------------------------------------------------------------------------");linkedList.print();System.out.println("删除10");linkedList.deleteById(10);System.out.println("删除1");linkedList.deleteById(1);linkedList.print();System.out.println("删除3");linkedList.deleteById(3);linkedList.print();System.out.println("删除4");linkedList.deleteById(4);linkedList.print();System.out.println("删除2");linkedList.deleteById(2);linkedList.print();System.out.println();}
}

打印信息

正序打印测试---------------------------------------------------------------------------------------
HeroNode [id=5, name=小明, nickname=小明]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=1, name=宋江, nickname=及时雨]
HeroNode [id=4, name=林冲, nickname=豹子头]
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=3, name=吴用, nickname=智多星]逆序打印测试---------------------------------------------------------------------------------------
HeroNode [id=3, name=吴用, nickname=智多星]
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=4, name=林冲, nickname=豹子头]
HeroNode [id=1, name=宋江, nickname=及时雨]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]获取链表长度测试---------------------------------------------------------------------------------------
链表长度：8反转链表测试---------------------------------------------------------------------------------------
HeroNode [id=3, name=吴用, nickname=智多星]
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=4, name=林冲, nickname=豹子头]
HeroNode [id=1, name=宋江, nickname=及时雨]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]修改链表元素测试---------------------------------------------------------------------------------------
HeroNode [id=3, name=吴用, nickname=智多星]
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=4, name=武松, nickname=行者]
HeroNode [id=1, name=宋江, nickname=及时雨]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]根据id查询元素---------------------------------------------------------------------------------------
linkedList.getById(2):HeroNode [id=2, name=卢俊义, nickname=玉麒麟]删除链表元素测试---------------------------------------------------------------------------------------
HeroNode [id=3, name=吴用, nickname=智多星]
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=4, name=武松, nickname=行者]
HeroNode [id=1, name=宋江, nickname=及时雨]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]
删除10
没有找到相应id的元素，无需删除
删除1
HeroNode [id=3, name=吴用, nickname=智多星]
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=4, name=武松, nickname=行者]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]
删除3
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=4, name=武松, nickname=行者]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]
删除4
HeroNode [id=2, name=卢俊义, nickname=玉麒麟]
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]
删除2
HeroNode [id=8, name=李华, nickname=李华]
HeroNode [id=7, name=小华, nickname=小华]
HeroNode [id=6, name=小花, nickname=小花]
HeroNode [id=5, name=小明, nickname=小明]Process finished with exit code 0

习题

反转链表

https://leetcode.cn/problems/fan-zhuan-lian-biao-lcof/

/*** 注意：head上面也有值，不是单纯作为头节点* @param head* @return*/
public ListNode reverseList(ListNode head) {ListNode cur = head;ListNode last = null;while (cur != null) {//先将cur后面的部分存储起来ListNode temp = cur.next;cur.next = last;last = cur;cur = temp;}return last;
}

删除链表的节点

https://leetcode.cn/problems/shan-chu-lian-biao-de-jie-dian-lcof/

public ListNode deleteNode(ListNode head, int val) {if (head == null) {return null;}if (head.val == val) {//删除头节点，直接返回头节点的下一个节点即可return head.next;}ListNode temp = head;while (temp != null && temp.next != null) {if (temp.next.val == val) {if (temp.next.next != null) {temp.next = temp.next.next;} else {temp.next = null;}break;}temp = temp.next;}return head;
}

删除链表的倒数第k个节点

https://leetcode.cn/problems/lian-biao-zhong-dao-shu-di-kge-jie-dian-lcof/

public ListNode getKthFromEnd(ListNode head, int k) {ListNode fast = head;ListNode slow = head;//让快指针先走k步for (int i = 0; i < k; i++) {fast = fast.next;}//快慢一起走，快走到尽头，慢就是倒数第k个while (true) {if (fast == null) {break;}fast = fast.next;slow = slow.next;}return slow;
}