1. 链表介绍

- 链表是以节点的方式来存储,是链式存储
- 每个节点包含 data 域,next 域:指向下一个节点
- 链表的各个节点的内存地址不一定是连续存储
- 链表分带头节点的链表和没有头节点的链表,根据实际的需求来确定

2. 应用实例
- 使用带head头的单向链表实现 –水浒英雄排行榜管理;完成对英雄人物的增删改查操作
- 代码实现
package com.datastructure.列表;
public class SingleLinkedListDemo {
public static void main(String[] args) {
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");
SingleLinkedList singleLinkedList = new SingleLinkedList();
singleLinkedList.add(hero1);
singleLinkedList.add(hero4);
singleLinkedList.add(hero3);
singleLinkedList.add(hero2);
System.out.println("随机插入");
singleLinkedList.list();
SingleLinkedList singleLinkedList2 = new SingleLinkedList();
singleLinkedList2.addByOrder(hero1);
singleLinkedList2.addByOrder(hero4);
singleLinkedList2.addByOrder(hero3);
singleLinkedList2.addByOrder(hero2);
System.out.println("顺序插入");
singleLinkedList2.list();
HeroNode newHeroNode = new HeroNode(2, "小卢", "玉麒麟");
singleLinkedList2.update(newHeroNode);
System.out.println("修改后的链表");
singleLinkedList2.list();
singleLinkedList2.del(1);
singleLinkedList2.del(4);
System.out.println("删除后的链表");
singleLinkedList2.list();
}
}
class HeroNode {
public int no;
public String name;
public String nickName;
public HeroNode next;
public HeroNode(int no, String name, String nickName) {
this.no = no;
this.name = name;
this.nickName = nickName;
}
@Override
public String toString() {
return "HeroNode{" +
"no=" + no +
", name='" + name + '\'' +
", nickName='" + nickName + '\'' +
'}';
}
}
class SingleLinkedList {
private HeroNode head = new HeroNode(0, "", "");
public void add(HeroNode heroNode) {
HeroNode temp = head;
while (true) {
if (temp.next == null) {
break;
}
temp = temp.next;
}
temp.next = heroNode;
}
public void addByOrder(HeroNode heroNode) {
HeroNode temp = head;
boolean flag = false;
while (true) {
if (temp.next == null) {
break;
}
if (temp.next.no > heroNode.no) {
break;
} else if (temp.next.no == heroNode.no) {
flag = true;
break;
}
temp = temp.next;
}
if (flag) {
System.out.printf("序号%d已存在,不能添加\n", heroNode.no);
} else {
heroNode.next = temp.next;
temp.next = heroNode;
}
}
public void update(HeroNode newHeroNode) {
if (head.next == null) {
System.out.println("链表为空");
return;
}
HeroNode temp = head.next;
boolean flag = false;
while (true) {
if (temp == null) {
break;
}
if (temp.no == newHeroNode.no) {
flag = true;
break;
}
temp = temp.next;
}
if (flag) {
temp.name = newHeroNode.name;
temp.nickName = newHeroNode.nickName;
} else {
System.out.printf("%d号节点不存在,修改失败\n", newHeroNode.no);
}
}
public void del(int no) {
HeroNode temp = head;
boolean flag = false;
while (true) {
if (temp.next == null) {
break;
}
if (temp.next.no == no) {
flag = true;
break;
}
temp = temp.next;
}
if (flag) {
temp.next = temp.next.next;
} else {
System.out.printf("待删除的%d号节点不存在\n", no);
}
}
public void list() {
if (head.next == null) {
System.out.println("链表为空");
return;
}
HeroNode temp = head.next;
while (true) {
if (temp == null) {
break;
} else {
System.out.println(temp);
temp = temp.next;
}
}
}
}
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随机插入
HeroNode{no=1, name='宋江', nickName='及时雨'}
HeroNode{no=4, name='林冲', nickName='豹子头'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
顺序插入
HeroNode{no=1, name='宋江', nickName='及时雨'}
HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=4, name='林冲', nickName='豹子头'}
修改后的链表
HeroNode{no=1, name='宋江', nickName='及时雨'}
HeroNode{no=2, name='小卢', nickName='玉麒麟'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=4, name='林冲', nickName='豹子头'}
删除后的链表
HeroNode{no=2, name='小卢', nickName='玉麒麟'}
HeroNode{no=3, name='吴用', nickName='智多星'}
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3. 单链表面试题
3.1 有效节点的个数
public static int getLength(HeroNode head) {
if (head.next == null) {
return 0;
}
int length = 0;
HeroNode temp = head.next;
while (temp != null) {
length++;
temp = temp.next;
}
return length;
}
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3.2 查找单链表中的倒数第k个结点
public static HeroNode findLastIndexNode(HeroNode head, int index) {
if (head == null) {
return null;
}
int length = getLength(head);
if (length <= 0 || index > length) {
return null;
}
HeroNode temp = head.next;
for (int i = 0; i < length - index; i++) {
temp = temp.next;
}
return temp;
}
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3.3 单链表的反转

1. 先定义一个临时节点 reverseHead = new HeroNode();
2. 从头到尾遍历原来的链表,每遍历一个节点,就将其取出,并放在新的链表头节点 reverseHead 的next
3. 原来的链表的head.next = reverseHead.next
public static void reverseList(HeroNode head) {
if (head.next == null || head.next.next == null) {
return;
}
HeroNode cur = head.next;
HeroNode next = null;
HeroNode reverseHead = new HeroNode(0, "", "");
while (cur != null) {
next = cur.next;
cur.next = reverseHead.next;
reverseHead.next = cur;
cur = next;
}
head.next = reverseHead.next;
}
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3.4 从尾到头打印单链表
1. 逆序打印单链表.
2. 方式1: 先将单链表进行反转操作,然后再遍历即可,这样的做的问题是会破坏原来的单链表的结构,不建议
3. 方式2:可以利用栈这个数据结构,将各个节点压入到栈中,然后利用栈的先进后出的特点,就实现了逆序打印的效果.
public static void reversePrint(HeroNode head) {
if (head.next == null) {
return;
}
Stack<HeroNode> stack = new Stack<>();
HeroNode temp = head.next;
while (temp != null) {
stack.push(temp);
temp = temp.next;
}
while (stack.size() > 0) {
System.out.println(stack.pop());
}
}
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3.5 完整代码
import java.util.Stack;
public class SingleLinkedListDemo {
public static void main(String[] args) {
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");
SingleLinkedList singleLinkedList = new SingleLinkedList();
singleLinkedList.add(hero1);
singleLinkedList.add(hero4);
singleLinkedList.add(hero3);
singleLinkedList.add(hero2);
System.out.println("随机插入");
singleLinkedList.list();
SingleLinkedList singleLinkedList2 = new SingleLinkedList();
singleLinkedList2.addByOrder(hero1);
singleLinkedList2.addByOrder(hero4);
singleLinkedList2.addByOrder(hero3);
singleLinkedList2.addByOrder(hero2);
System.out.println("顺序插入");
singleLinkedList2.list();
System.out.println("list2的倒数第3个节点是:" + findLastIndexNode(singleLinkedList2.getHead(), 3));
reverseList(singleLinkedList2.getHead());
System.out.println("显示反转后的结果");
singleLinkedList2.list();
System.out.println("逆序打印");
reversePrint(singleLinkedList2.getHead());
HeroNode newHeroNode = new HeroNode(2, "小卢", "玉麒麟");
singleLinkedList2.update(newHeroNode);
System.out.println("修改后的链表");
singleLinkedList2.list();
singleLinkedList2.del(1);
singleLinkedList2.del(4);
System.out.println("删除后的链表");
singleLinkedList2.list();
System.out.println("singleLinkedList2有效节点数=" + getLength(singleLinkedList2.getHead()));
}
public static int getLength(HeroNode head) {
if (head.next == null) {
return 0;
}
int length = 0;
HeroNode temp = head.next;
while (temp != null) {
length++;
temp = temp.next;
}
return length;
}
public static HeroNode findLastIndexNode(HeroNode head, int index) {
if (head == null) {
return null;
}
int length = getLength(head);
if (length <= 0 || index > length) {
return null;
}
HeroNode temp = head.next;
for (int i = 0; i < length - index; i++) {
temp = temp.next;
}
return temp;
}
public static void reverseList(HeroNode head) {
if (head.next == null || head.next.next == null) {
return;
}
HeroNode cur = head.next;
HeroNode next = null;
HeroNode reverseHead = new HeroNode(0, "", "");
while (cur != null) {
next = cur.next;
cur.next = reverseHead.next;
reverseHead.next = cur;
cur = next;
}
head.next = reverseHead.next;
}
public static void reversePrint(HeroNode head) {
if (head.next == null) {
return;
}
Stack<HeroNode> stack = new Stack<>();
HeroNode temp = head.next;
while (temp != null) {
stack.push(temp);
temp = temp.next;
}
while (stack.size() > 0) {
System.out.println(stack.pop());
}
}
}
class HeroNode {
public int no;
public String name;
public String nickName;
public HeroNode next;
public HeroNode(int no, String name, String nickName) {
this.no = no;
this.name = name;
this.nickName = nickName;
}
@Override
public String toString() {
return "HeroNode{" +
"no=" + no +
", name='" + name + '\'' +
", nickName='" + nickName + '\'' +
'}';
}
}
class SingleLinkedList {
private HeroNode head = new HeroNode(0, "", "");
public HeroNode getHead() {
return head;
}
public void add(HeroNode heroNode) {
HeroNode temp = head;
while (true) {
if (temp.next == null) {
break;
}
temp = temp.next;
}
temp.next = heroNode;
}
public void addByOrder(HeroNode heroNode) {
HeroNode temp = head;
boolean flag = false;
while (true) {
if (temp.next == null) {
break;
}
if (temp.next.no > heroNode.no) {
break;
} else if (temp.next.no == heroNode.no) {
flag = true;
break;
}
temp = temp.next;
}
if (flag) {
System.out.printf("序号%d已存在,不能添加\n", heroNode.no);
} else {
heroNode.next = temp.next;
temp.next = heroNode;
}
}
public void update(HeroNode newHeroNode) {
if (head.next == null) {
System.out.println("链表为空");
return;
}
HeroNode temp = head.next;
boolean flag = false;
while (true) {
if (temp == null) {
break;
}
if (temp.no == newHeroNode.no) {
flag = true;
break;
}
temp = temp.next;
}
if (flag) {
temp.name = newHeroNode.name;
temp.nickName = newHeroNode.nickName;
} else {
System.out.printf("%d号节点不存在,修改失败\n", newHeroNode.no);
}
}
public void del(int no) {
HeroNode temp = head;
boolean flag = false;
while (true) {
if (temp.next == null) {
break;
}
if (temp.next.no == no) {
flag = true;
break;
}
temp = temp.next;
}
if (flag) {
temp.next = temp.next.next;
} else {
System.out.printf("待删除的%d号节点不存在\n", no);
}
}
public void list() {
if (head.next == null) {
System.out.println("链表为空");
return;
}
HeroNode temp = head.next;
while (true) {
if (temp == null) {
break;
} else {
System.out.println(temp);
temp = temp.next;
}
}
}
}
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随机插入
HeroNode{no=1, name='宋江', nickName='及时雨'}
HeroNode{no=4, name='林冲', nickName='豹子头'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
顺序插入
HeroNode{no=1, name='宋江', nickName='及时雨'}
HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=4, name='林冲', nickName='豹子头'}
list2的倒数第3个节点是:HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
显示反转后的结果
HeroNode{no=4, name='林冲', nickName='豹子头'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
HeroNode{no=1, name='宋江', nickName='及时雨'}
逆序打印
HeroNode{no=1, name='宋江', nickName='及时雨'}
HeroNode{no=2, name='卢俊义', nickName='玉麒麟'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=4, name='林冲', nickName='豹子头'}
修改后的链表
HeroNode{no=4, name='林冲', nickName='豹子头'}
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=2, name='小卢', nickName='玉麒麟'}
HeroNode{no=1, name='宋江', nickName='及时雨'}
删除后的链表
HeroNode{no=3, name='吴用', nickName='智多星'}
HeroNode{no=2, name='小卢', nickName='玉麒麟'}
singleLinkedList2有效节点数=2
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