文章目录
- 链表
- 双向链表
链表
/**
* Node类，表示需要添加到链表中的元素，
* element：保存要加入链表元素的值
* next：指向链表中下一个元素的指针
*/
class Node {
constructor(element) {
this.element = element;
this.next = undefined;
}
}
const defaultEquals = (a,) => {
return a === b;
}
class LinkedList {
constructor(equalsFn =) {
this.count = 0; // 保存链表元素的数量
this.head = undefined; // 保存元素的引用
this.equalsFn = equalsFn; // 比较链表中元素是否相等
}
// 链表尾部添加元素
push(element) {
const node = new Node(element);
let current;
if (this.head == null) {
this.head = node;
} else {
current = this.head;
while (current.next != null) {
current = current.next;
}
current.next = node
}
this.count++;
}
// 向链表指定位置插入元素
insert(element,) {
if (index >= 0 && index <= this.count) {
const node = new Node(element);
if (index === 0) {
const current = this.head;
node.next = current;
this.head = node;
} else {
const previous = this.getElementAt(index - 1);
const current = previous.next;
node.next = current;
previous.next = node
}
this.count++;
return true;
}
return false
}
// 返回链表指定位置的元素
getElementAt(index) {
if (index >= 0 && index <= this.count) {
let node = this.head;
for (let i = 0; i < index && node != null; i++) {
node = node.next
}
return node
}
return undefined
}
// 返回元素在链表中的索引
indexOf(element) {
let current = this.head;
for (let i = 0; i < this.count && current != null; i++) {
if (this.equalsFn(element, current.element)) {
return i
}
current = current.next;
}
return -1
}
// 从链表的指定索引删除一个元素
removeAt(index) {
// 边界检查
if (index >= 0 && index < this.count) {
let current = this.head;
// 删除第一个元素
if (index === 0) {
this.head = current.next;
} else {
const previous = this.getElementAt(index - 1);
current = previous.next;
previous.next = current.next;
}
this.count--;
return current.element
}
return undefined;
}
// 判断链表是否为空
isEmpty() {
return this.count === 0;
}
// 链表长度
size() {
return this.count;
}
getHead() {
return this.head
}
// 返回链表的字符串
toString() {
if (this.head == null) return '';
let objString = `${this.head.element}`;
let current = this.head.next;
for (let index = 0; index < this.size() && current != null; index++) {
objString = `${objString},${current.element}`
current = current.next;
}
return objString;
}
// 删除元素
remove(element) {
const index = this.indexOf(element);
return this.removeAt(index)
}
}
const link = new LinkedList();
link.push(12);
link.push(132);
console.log("原始链表", link)
console.log(link.removeAt(0))
console.log("删除后的链表", link)
link.insert(32, 0)
console.log("insert后链表", link)
console.log("indexOf元素", link.indexOf(132))
console.log("remove元素", link.remove(132))
console.log("remove后的链表", link)
link.push(90)
console.log("链表的head", link.getHead())
console.log("链表元素", link.toString())
双向链表
// 双向链表的节点，继承Node节点的element和next属性
class DoublyNode extends Node {
constructor(element, next,) {
super(element, next);
this.prev = prev;
}
}
class DoublyLinkedList extends LinkedList {
constructor(equalsFn =) {
super(equalsFn);
this.tail = undefined;// 双向链表的尾部
}
// 添加元素
push(element) {
const node = new DoublyNode(element);
/**
* 如果head为null，那么链表为空，添加的元素为第一项也是尾项
*/
if (this.head == null) {
this.head = node;
this.tail = node
} else {
// 从链表尾部添加元素
this.tail.next = node;
node.prev = this.tail;
this.tail = node;
}
this.count++;
}
insert(element,) {
if (index >= 0 && index <= this.count) {
const node = new DoublyNode(element);
let current = this.head;
if (index === 0) {
if (this.head == null) {
this.head = node;
this.tail = node;
} else {
node.next = this.head;
this.head.prev = node;
this.head = node;
}
} else if (index === this.count) {
current = this.tail;
current.next = node;
node.prev = current;
this.tail = node
} else {
const previous = this.getElementAt(index - 1);
console.log("===", this.getElementAt(index - 1))
current = previous.next;
node.next = current;
previous.next = node;
current.prev = node;
node.prev = previous;
}
this.count++;
return true
}
return false
}
// 删除元素
removeAt(index) {
if (index >= 0 && index < this.count) {
let current = this.head;
if (index === 0) {
this.head = this.head.next;
// 如果只有一项，更新tail
if (this.count === 1) {
this.tail = undefined;
} else {
this.head.prev = undefined;
}
} else if (index === this.count - 1) {
// 如果删除的是最后一项
current = this.tail;
this.tail = current.prev;
this.tail.next = undefined;
} else {
current = this.getElementAt(index);
const previous = current.prev;
previous.next = current.prev;
current.next.prev = previous;
}
this.count--;
return current.element
}
return undefined;
}
indexOf(element) {
let current = this.head;
let index = 0;
while (current != null) {
if (this.equalsFn(element, current.element)) {
return index
}
index++;
current = current.next;
}
return -1;
}
getHead() {
return this.head;
}
getTail() {
return this.tail;
}
clear() {
super.clear();
this.tail = undefined;
}
toString() {
if (this.head == null) return "";
let objString = `${this.head.element}`;
let current = this.head.next;
while (current != null) {
objString = `${objString},${current.element}`;
current = current.next;
}
return objString;
}
inverseToString() {
if (this.tail == null) return '';
let objString = `${this.tail.element}`;
let previous = this.tail.prev;
while (previous != null) {
objString = `${objString},${previous.element}`;
previous = previous.prev;
}
return objString;
}
}
const link = new DoublyLinkedList();
link.push(122)
link.push(124)
link.insert(1, 1)
link.push(102)
console.log(link);
console.log("removeAt", link.removeAt(1))
console.log("removeAt link", link);
console.log(link.inverseToString())
