链表js实现
链表的基本概念
链表是一种线性数据结构，由一系列节点组成，每个节点包含数据部分和指向下一个节点的指针。与数组不同，链表在内存中是非连续存储的，插入和删除操作的时间复杂度为 O(1)，但访问元素的时间复杂度为 O(n)。
单向链表的实现
单向链表是最简单的链表形式，每个节点只有一个指针指向下一个节点。
class ListNode {
constructor(data) {
this.data = data;
this.next = null;
}
}
class LinkedList {
constructor() {
this.head = null;
this.size = 0;
}
// 在链表末尾添加节点
append(data) {
const newNode = new ListNode(data);
if (!this.head) {
this.head = newNode;
} else {
let current = this.head;
while (current.next) {
current = current.next;
}
current.next = newNode;
}
this.size++;
}
// 在指定位置插入节点
insertAt(data, index) {
if (index < 0 || index > this.size) return false;
const newNode = new ListNode(data);
if (index === 0) {
newNode.next = this.head;
this.head = newNode;
} else {
let current = this.head;
let prev = null;
let i = 0;
while (i < index) {
prev = current;
current = current.next;
i++;
}
newNode.next = current;
prev.next = newNode;
}
this.size++;
return true;
}
// 删除指定位置的节点
removeAt(index) {
if (index < 0 || index >= this.size) return null;
let removedNode;
if (index === 0) {
removedNode = this.head;
this.head = this.head.next;
} else {
let current = this.head;
let prev = null;
let i = 0;
while (i < index) {
prev = current;
current = current.next;
i++;
}
removedNode = current;
prev.next = current.next;
}
this.size--;
return removedNode.data;
}
// 获取指定位置的数据
getAt(index) {
if (index < 0 || index >= this.size) return null;
let current = this.head;
let i = 0;
while (i < index) {
current = current.next;
i++;
}
return current.data;
}
// 打印链表
print() {
let current = this.head;
let result = [];
while (current) {
result.push(current.data);
current = current.next;
}
console.log(result.join(' -> '));
}
}双向链表的实现
双向链表每个节点有两个指针，分别指向前一个节点和后一个节点，便于双向遍历。
class DoublyListNode {
constructor(data) {
this.data = data;
this.prev = null;
this.next = null;
}
}
class DoublyLinkedList {
constructor() {
this.head = null;
this.tail = null;
this.size = 0;
}
// 在链表末尾添加节点
append(data) {
const newNode = new DoublyListNode(data);
if (!this.head) {
this.head = newNode;
this.tail = newNode;
} else {
newNode.prev = this.tail;
this.tail.next = newNode;
this.tail = newNode;
}
this.size++;
}
// 在指定位置插入节点
insertAt(data, index) {
if (index < 0 || index > this.size) return false;
const newNode = new DoublyListNode(data);
if (index === 0) {
if (!this.head) {
this.head = newNode;
this.tail = newNode;
} else {
newNode.next = this.head;
this.head.prev = newNode;
this.head = newNode;
}
} else if (index === this.size) {
newNode.prev = this.tail;
this.tail.next = newNode;
this.tail = newNode;
} else {
let current = this.head;
let i = 0;
while (i < index) {
current = current.next;
i++;
}
newNode.prev = current.prev;
newNode.next = current;
current.prev.next = newNode;
current.prev = newNode;
}
this.size++;
return true;
}
// 删除指定位置的节点
removeAt(index) {
if (index < 0 || index >= this.size) return null;
let removedNode;
if (index === 0) {
removedNode = this.head;
if (this.size === 1) {
this.head = null;
this.tail = null;
} else {
this.head = this.head.next;
this.head.prev = null;
}
} else if (index === this.size - 1) {
removedNode = this.tail;
this.tail = this.tail.prev;
this.tail.next = null;
} else {
let current = this.head;
let i = 0;
while (i < index) {
current = current.next;
i++;
}
removedNode = current;
current.prev.next = current.next;
current.next.prev = current.prev;
}
this.size--;
return removedNode.data;
}
// 打印链表
print() {
let current = this.head;
let result = [];
while (current) {
result.push(current.data);
current = current.next;
}
console.log(result.join(' <-> '));
}
}链表的使用示例
// 单向链表示例
const list = new LinkedList();
list.append(10);
list.append(20);
list.append(30);
list.insertAt(15, 1);
list.print(); // 输出: 10 -> 15 -> 20 -> 30
list.removeAt(2);
list.print(); // 输出: 10 -> 15 -> 30
// 双向链表示例
const dList = new DoublyLinkedList();
dList.append(10);
dList.append(20);
dList.append(30);
dList.insertAt(15, 1);
dList.print(); // 输出: 10 <-> 15 <-> 20 <-> 30
dList.removeAt(2);
dList.print(); // 输出: 10 <-> 15 <-> 30链表的应用场景
链表适用于需要频繁插入和删除操作的场景，如实现队列、栈、哈希表的链地址法等。由于其动态内存分配的特性，链表在内存利用率上比数组更灵活。
