Free learning recommendation: java basic tutorial
##Article directory
1. Introduction to singly linked list
Singly linked list is anordered list that stores information in the form of node, but the node does not Must be continuous , each node includes data field and next field.
The linked list is divided into
and the linked list without the head node.
Singly linked list (without leading node)
Requirements: Use1. Creation (addition) of a singly linked listsingle linked list with header to implement – Water Margin hero ranking management.
1) Complete the addition, deletion, modification and check of the hero2) When adding a hero in the first method,is directly added to the end of the linked list
.3) In the second method, when adding a hero, insert the herointo the specified position according to the ranking
(if the ranking already exists, the addition will fail and a prompt will be given)
1.1 Adding the tail
The idea of adding the tail
①
First create a head node, which is used to represent the head of a singly linked list. ② Then every time a node is added, it is added directly to the end of the linked list. Tail addition means: regardless of the numbering sequence, find the last node of the current linked list, and point the next of the last node to the new node.
Code implementation // 添加方式1:尾添加
public void add(HeroNode heroNode) {
// 因为head头不能动,因此需要一个辅助变量(指针)temp
HeroNode temp = head;
while (true) {
// 如果遍历到链表的最后
if (temp.next == null) {
break;
}
// temp指针后移
temp = temp.next;
}
// 当退出循环时,temp指向链表的最后
temp.next = heroNode;
}
Ideas of adding by ranking
①First find the location of the newly added node through the auxiliary variable (temp pointer). ②New node.next=temp.next; ③temp.next=New node;
// 添加方式2:根据排名添加
public void addByOrder(HeroNode heroNode) {
HeroNode temp = head;// 借助辅助指针
boolean flag = false;// 添加的编号是否存在
while (true) {
if (temp.next == null) {// 遍历到结尾
break;
}
if (temp.next.no > heroNode.no) {// 位置找到,就在temp的后面插入
break;
} else if (temp.next.no == heroNode.no) {// 该编号已存在
flag = true;
break;
}
temp = temp.next;// 后移,遍历当前链表
}
if (flag) {
// 不能添加
System.out.printf("准备插入的英雄的编号%d已经存在，不能加入\n", heroNode.no);
} else {
// 插入到temp的后面
heroNode.next = temp.next;
temp.next = heroNode;
}
}
Modification ideas
①Find the node first through traversal. ②temp.name =newHeroNode.name;
, temp.nickname=newHeroNode.nickname;
// 修改节点信息,根据节点的no属性修改其他信息
public void update(HeroNode newHeroNode) {
// 空链表无法修改节点信息
if (head.next == null) {
System.out.println("链表为空~");
return;
}
// 根据no排名找到需要修改的节点
HeroNode temp = head.next;
boolean flag = false;// flag表示是否找到需要修改的节点
while (true) {
if (temp == null) {
// 遍历到结尾
break;
}
if (temp.no == newHeroNode.no) {
// 找到
flag = true;
break;
}
temp = temp.next;// 后移
}
if (flag) {
temp.name = newHeroNode.name;
temp.nickname = newHeroNode.nickname;
} else {
System.out.printf("没有找到编号为%d的节点，不能修改\n", newHeroNode.no);
}
}
Deletion ideas
①
Find the node that needs to be deleted the previous node. ②temp.next=temp.next.next ③The deleted node will not have other references pointing to it and will be recycled by the garbage collection mechanism. 
Code implementation public void delete(int no) {
HeroNode temp = head;
boolean flag = false;// 是否找到待删除节点
while (true) {
if (temp.next == null) {
// 遍历到结尾
break;
}
if (temp.next.no == no) {
// 找到了待删除节点的前一个节点
flag = true;
break;
}
temp = temp.next;// 后移
}
if (flag) {
// 可以删除
temp.next = temp.next.next;
} else {
System.out.printf("要删除的%d节点不存在\n", no);
}
}
package com.gql.linkedlist;/**
* 单链表
*
* @guoqianliang
*
*/public class SingleLinkedListDemo {
public static void main(String[] args) {
// 创建节点
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");
// 创建单向链表
SingleLinkedList singleLinkedList = new SingleLinkedList();
// 加入
singleLinkedList.addByOrder(hero1);
singleLinkedList.addByOrder(hero4);
singleLinkedList.addByOrder(hero3);
singleLinkedList.addByOrder(hero2);
singleLinkedList.list();
// 测试修改节点
HeroNode newHeroNode = new HeroNode(2, "小卢", "玉麒麟~");
singleLinkedList.update(newHeroNode);
System.out.println("修改后的链表情况:");
singleLinkedList.list();
// 删除一个节点
singleLinkedList.delete(1);
singleLinkedList.delete(2);
singleLinkedList.delete(3);
singleLinkedList.delete(4);
System.out.println("删除后的链表情况:");
singleLinkedList.list();
}}//定义SingleLinkedList,管理英雄class SingleLinkedList {
// 初始化头结点,不存放具体数据
private HeroNode head = new HeroNode(0, "", "");
// 添加方式1:尾添加
// 思路:
// 1.找到当前链表的最后节点
// 2.将这个最后的节点的next指向新的节点
public void add(HeroNode heroNode) {
// 因为head头不能动,因此需要一个辅助变量(指针)temp
HeroNode temp = head;
while (true) {
// 如果遍历到链表的最后
if (temp.next == null) {
break;
}
// temp指针后移
temp = temp.next;
}
// 当退出循环时,temp指向链表的最后
temp.next = heroNode;
}
// 添加方式2:根据排名添加
public void addByOrder(HeroNode heroNode) {
HeroNode temp = head;// 借助辅助指针
boolean flag = false;// 添加的编号是否存在
while (true) {
if (temp.next == null) {// 遍历到结尾
break;
}
if (temp.next.no > heroNode.no) {// 位置找到,就在temp的后面插入
break;
} else if (temp.next.no == heroNode.no) {// 该编号已存在
flag = true;
break;
}
temp = temp.next;// 后移,遍历当前链表
}
if (flag) {
// 不能添加
System.out.printf("准备插入的英雄的编号%d已经存在，不能加入\n", heroNode.no);
} else {
// 插入到temp的后面
heroNode.next = temp.next;
temp.next = heroNode;
}
}
// 修改节点信息,根据节点的no属性修改其他信息
public void update(HeroNode newHeroNode) {
// 空链表无法修改节点信息
if (head.next == null) {
System.out.println("链表为空~");
return;
}
// 根据no排名找到需要修改的节点
HeroNode temp = head.next;
boolean flag = false;// flag表示是否找到需要修改的节点
while (true) {
if (temp == null) {
// 遍历到结尾
break;
}
if (temp.no == newHeroNode.no) {
// 找到
flag = true;
break;
}
temp = temp.next;// 后移
}
if (flag) {
temp.name = newHeroNode.name;
temp.nickname = newHeroNode.nickname;
} else {
System.out.printf("没有找到编号为%d的节点，不能修改\n", newHeroNode.no);
}
}
// 删除节点
// 思路:
// 1.找到需要删除节点的前一个节点
// 2.temp.next=temp.next.next
// 3.被删除的节点将会被垃圾回收机制回收
public void delete(int no) {
HeroNode temp = head;
boolean flag = false;// 是否找到待删除节点
while (true) {
if (temp.next == null) {
// 遍历到结尾
break;
}
if (temp.next.no == no) {
// 找到了待删除节点的前一个节点
flag = true;
break;
}
temp = temp.next;// 后移
}
if (flag) {
// 可以删除
temp.next = temp.next.next;
} else {
System.out.printf("要删除的%d节点不存在\n", no);
}
}
// 显示链表[遍历]
public void list() {
// 空链表直接返回
if (head.next == null) {
System.out.println("链表为空");
return;
}
// 仍然使用辅助变量(指针),进行循环
HeroNode temp = head.next;
while (true) {
if (temp == null) {
break;
}
System.out.println(temp);
// 将temp后移
temp = temp.next;
}
}}//定义HeroNode,每一个HeroNode就是一个节点class HeroNode {
public int no;// 排名
public String name;
public String nickname;// 昵称
public HeroNode next;// 指向下一个节点
// 构造器
public HeroNode() {
super();
}
public HeroNode(int no, String name, String nickname) {
super();
this.no = no;
this.name = name;
this.nickname = nickname;
}
// 重写toString
@Override
public String toString() {
return "HeroNode [no=" + no + ", name=" + name + ", nickname=" + nickname + "]";
}}
The answers to the above four interview questions are In the following code
package com.gql.LinkedList;import java.util.Stack;/**
* 模拟单链表
*
* @author Hudie
* @Email:guoqianliang@foxmail.com
* @date 2020年7月16日下午6:47:42
*/public class SingleLinkedListDemo {
public static void main(String[] args) {
// 创建节点
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");
// 创建单向链表
SingleLinkedList singleLinkedList = new SingleLinkedList();
// 加入
singleLinkedList.addByOrder(hero1);
singleLinkedList.addByOrder(hero4);
singleLinkedList.addByOrder(hero3);
singleLinkedList.addByOrder(hero2);
singleLinkedList.list();
// 测试修改节点
HeroNode newHeroNode = new HeroNode(2, "小卢", "玉麒麟~");
singleLinkedList.update(newHeroNode);
System.out.println("修改后的链表情况:");
singleLinkedList.list();
// 删除一个节点
singleLinkedList.delete(4);
System.out.println("删除后的链表情况:");
singleLinkedList.list();
//练习4:反向打印单链表
System.out.println("反向打印单链表:");
reversePrint(singleLinkedList.getHead());
//练习3:反转单链表
reversalList(singleLinkedList.getHead());
System.out.println("反转过后的单链表为:");
singleLinkedList.list();
// 练习1:获取单链表节点个数
System.out.println("单链表的有效个数为:");
System.out.println(getLength(singleLinkedList.getHead()));
int index = 2;
//练习2:获取单链表倒数第index给节点
System.out.println("倒数第"+ index +"个节点为:");
System.out.println(getLastKNode(singleLinkedList.getHead(),index));
}
/**
* @Description: 获取单链表节点个数 思路: while循环 + 遍历指针
*/
public static int getLength(HeroNode head) {
if (head.next == null) {
return 0;
}
int length = 0;
// 辅助指针
HeroNode p = head.next;
while (p != null) {
length++;
p = p.next;
}
return length;
}
/**
* @Description:
* 查找单链表中倒数第index个节点 index:表示倒数第index给节点
* 思路:
* 1.首先获取链表的长度length,可直接调用getLength
* 2.然后从链表第一个开始遍历,遍历(length-index)个
* 3.找不到返回null
*/
public static HeroNode getLastKNode(HeroNode head, int index) {
if (head.next == null) {
return null;
}
int length = getLength(head);
if (index <= 0 || index > length) {
return null;
}
HeroNode p = head.next;
for(int i = 0;i < length-index;i++){
p = p.next;
}
return p;
}
/**
* @Description:
* 反转单链表[带头节点]
* 思路:
* 1.先定义一个节点reversalHead = new HeroNode(0,"","");
* 2.遍历原来的链表,每遍历一个节点,就将其取出,并放在新的链表reversalHead的最前端
* 3.原来的链表的head.next = reversalHead;
*/
public static void reversalList(HeroNode head){
//链表为空或只有一个节点,无需反转,直接返回
if(head.next == null || head.next.next == null){
return;
}
//辅助指针p
HeroNode p = head.next;
HeroNode next = null;//指向辅助指针p的下一个位置
HeroNode reversalHead = new HeroNode(0,"","");
//遍历原来的链表,每遍历一个节点,就将其取出,并放在新的链表reversalHead的最前端
while(p != null){
next = p.next;
p.next = reversalHead.next;
reversalHead.next = p;
p = next;
}
head.next = reversalHead.next;
}
/**
* @Description:
* 反向打印单链表[带头节点]
* 思路1:单链表反转后打印(不建议,因为破坏了单链表的结构)
* 思路2:使用栈结构,利用栈先进后出的特点
*/
public static void reversePrint(HeroNode head){
if(head.next == null){
return;
}
Stack stack = new Stack();
HeroNode p = head.next;
while(p != null){
stack.push(p);
p = p.next;
}
//将栈中的节点进行打印
while(stack.size() > 0){
System.out.println(stack.pop());
}
}}// 定义SingleLinkedList,管理英雄,即链表的增删改查class SingleLinkedList {
// 初始化头结点,不存放具体数据
private HeroNode head = new HeroNode(0, "", "");
// 添加方式1:尾添加
// 思路:
// 1.找到当前链表的最后节点
// 2.将这个最后的节点的next指向新的节点
public void add(HeroNode heroNode) {
// 因为head头不能动,因此需要一个辅助变量(指针)temp
HeroNode temp = head;
while (true) {
// 如果遍历到链表的最后
if (temp.next == null) {
break;
}
// temp指针后移
temp = temp.next;
}
// 当退出循环时,temp指向链表的最后
temp.next = heroNode;
}
public HeroNode getHead() {
return head;
}
// 添加方式2:根据排名添加
public void addByOrder(HeroNode heroNode) {
HeroNode temp = head;// 借助辅助指针
boolean flag = false;// 添加的编号是否存在
while (true) {
if (temp.next == null) {// 遍历到结尾
break;
}
if (temp.next.no > heroNode.no) {// 位置找到,就在temp的后面插入
break;
} else if (temp.next.no == heroNode.no) {// 该编号已存在
flag = true;
break;
}
temp = temp.next;// 后移,遍历当前链表
}
if (flag) {
// 不能添加
System.out.printf("准备插入的英雄的编号%d已经存在，不能加入\n", heroNode.no);
} else {
// 插入到temp的后面
heroNode.next = temp.next;
temp.next = heroNode;
}
}
// 修改节点信息,根据节点的no属性修改其他信息
public void update(HeroNode newHeroNode) {
// 空链表无法修改节点信息
if (head.next == null) {
System.out.println("链表为空~");
return;
}
// 根据no排名找到需要修改的节点
HeroNode temp = head.next;
boolean flag = false;// flag表示是否找到需要修改的节点
while (true) {
if (temp == null) {
// 遍历到结尾
break;
}
if (temp.no == newHeroNode.no) {
// 找到
flag = true;
break;
}
temp = temp.next;// 后移
}
if (flag) {
temp.name = newHeroNode.name;
temp.nickname = newHeroNode.nickname;
} else {
System.out.printf("没有找到编号为%d的节点，不能修改\n", newHeroNode.no);
}
}
// 删除节点
// 思路:
// 1.找到需要删除节点的前一个节点
// 2.temp.next=temp.next.next
// 3.被删除的节点将会被垃圾回收机制回收
public void delete(int no) {
HeroNode temp = head;
boolean flag = false;// 是否找到待删除节点
while (true) {
if (temp.next == null) {
// 遍历到结尾
break;
}
if (temp.next.no == no) {
// 找到了待删除节点的前一个节点
flag = true;
break;
}
temp = temp.next;// 后移
}
if (flag) {
// 可以删除
temp.next = temp.next.next;
} else {
System.out.printf("要删除的%d节点不存在\n", no);
}
}
// 显示链表[遍历]
public void list() {
// 空链表直接返回
if (head.next == null) {
System.out.println("链表为空");
return;
}
// 仍然使用辅助变量(指针),进行循环
HeroNode temp = head.next;
while (true) {
if (temp == null) {
break;
}
System.out.println(temp);
// 将temp后移
temp = temp.next;
}
}}// 定义HeroNode,每一个HeroNode就是一个节点class HeroNode {
public int no;// 排名
public String name;
public String nickname;// 昵称
public HeroNode next;// 指向下一个节点
// 构造器
public HeroNode() {
super();
}
public HeroNode(int no, String name, String nickname) {
super();
this.no = no;
this.name = name;
this.nickname = nickname;
}
// 重写toString
@Override
public String toString() {
return "HeroNode [no=" + no + ", name=" + name + ", nickname=" + nickname + "]";
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