昨天写链表出现了一些问题，而且现有教材有些代码陈旧，没有使用ES6语法，于是啃了一天的ES6，笔记还在整理，整理好了会发上来。
这个单向链表开始理解很难，但彻底理解了之后就茅塞顿开，写起来很顺畅，而且获取链节点，删除链节点，获取位置等代码方法之间可以来回复用，真的太舒服了！！！
"use strict"
class ListNode {
constructor(element) {
this.element = element;
this.next = null;
}
}
class List {
// 构造函数
constructor() {
this.head = null;
this.length = 0;
}
// 在链表尾插入节点（√）
append (element) {
// 定义插入的节点
let node = new ListNode(element)
let current
if (this.head === null) {
this.head = node
} else {
current = this.head
while (current.next) {
current = current.next
}
current.next = node
}
this.length ++
}
// 从链表中移除元素
removeAt (position) {
// 检测输入是否合法
if (position <= 0 || position > this.length) {
return 'ERROR'
} else {
let current = this.head
let previous
let index = 1
// 寻找需要删除的节点
while (index++ < position ) {
previous = current
current = current.next
}
// 将此节点的next截断
// 将上一节点的next改为下一节点
previous.next = current.next
current.next = null
// 返回数组长度
this.length --
return current.element
}
}
// 从固定位置插入元素
// 插入位置为position 的前一位
insert (position, element) {
if (position < 1 || position > this.length) {
return 'ERROR'
} else {
let current = this.head
let previous
let index = 1
let node = new ListNode(element)
// 找到节点
while (index ++ < position) {
previous = current
current = current.next
}
previous.next = node
node.next = current
this.length ++
return '追加节点完成!'
}
}
// 将所有节点变成字符串输入、
// 可用于检查
toString () {
let current = this.head
let string = ''
let index = 1
while (index++ <= this.length) {
string += current.element
current = current.next
}
return string
}
// 根据元素内容查找节点，有则范围序号，无则返回-1
indexOf (element) {
let current = this.head
let index = 1
let output = -1
while (index++ <= this.length) {
if (current.element === element) {
// 此时index已经++
output = index - 1
break;
}
current = current.next
}
return output
}
// 查找元素并删除
// 代码复用
remove (element) {
let index = this.indexOf(element)
return this.removeAt(index)
}
// 返回链表长度
size () {
return this.length
}
// 检查是否为空
isEmpty () {
return this.length === 0 ? 'is null' : 'not null'
}
// 获取头文件
getHead () {
return this.head
}
// 测试用
// 显示所有链表节点
showAll () {
let current = this.head
let index = 1
console.log("----开始显示节点----");
while ( index ++ < this.length) {
console.log(current.element);
current = current.next
}
console.log(current.element);
return '----节点显示完成----'
}
}
// 测试
let list = new List()
for (let i = 1; i <= 5 ; i++) {
list.append(i)
}
console.log('链表长度为' + list.length);
console.log('测试开始===================');
console.log('==== 1. 测试移除节点 ====');
console.log(list.removeAt(3));
console.log('链表长度为：' + list.length);
console.log(list.showAll());
console.log('===========================');
console.log('==== 2. 测试追加节点 ====');
console.log(list.insert(2, 9999));
console.log('链表长度为：' + list.length);
console.log(list.showAll());
console.log('===========================');
console.log('==== 3. 测试toString ====');
console.log(list.toString());
console.log('链表长度为：' + list.length);
console.log(list.showAll());
console.log('===========================');
console.log('==== 4. 测试indexOf ====');
console.log(list.indexOf(9999));
console.log('链表长度为：' + list.length);
console.log(list.showAll());
console.log('===========================');
console.log('==== 5. 测试remove ====');
console.log(list.remove(9999));
console.log('链表长度为：' + list.length);
console.log(list.showAll());
console.log('===========================');
console.log('==== 6. 测试size ====');
console.log(list.size());
console.log('===========================');
console.log('==== 7. 测试isEmpty ====');
console.log(list.isEmpty());
console.log('===========================');
console.log('==== 8 测试getHead ====');
console.log(list.getHead());
console.log('===========================');
console.log('测试完成!');
