【前端】JavaScript 数据结构 -- 链表

JavaScript 数据结构 – 链表

1. 链表定义

1.1 定义

链表是一种使用任意单元存储线性表元素的数据结构，是一种链式存储的线性表，该种数据结构的特点：

1. 方便插入和删除
2. 不支持随机存取
3. 存储单元(元素)在内存中不一定连续
4. 链表中元素存储元素信息外，还含有指向下一个元素的指针域信息

1.2 示意图

1. head：链表头
2. Node：元素（结点）
3. info：元素信息
4. next：指向下一元素的指针域

1.3 链表支持方法

1. add(node)：增加一个结点
2. remove()：删除一个结点
3. size()：返回链表长度
4. isEmpty()：检测链表是否为空
5. get(index)：获取 index 下的元素

2. JavaScript 链表的实现

2.1 字面量声明

let list = {
    head:null,
    
    add: function(data) {
        let node = {
            data: data,
            next: null
        }
        if (this.head === null) {
            this.head = node
        } else {
            let pre = this.head;
            let next = this.head.next;
            while (next !== null) {
                pre = next;
                next = next.next;
            }
            pre.next = node;
        }
    },
    
    remove: function() {
        if (this.head === null || this.head.next === null) {
            this.head = null;
            return;
        }

        let pre = this.head;
        let next = this.head.next;
        while (next.next !== null) {
            pre = next;
            next = pre.next;
        }
        console.log(pre.data);
        pre.next = null;
    },

    isEmpty: function() {
        return this.head === null;
    },

    size: function() {
        if (this.head === null) {
            return 0;
        } 
        let size = 0;
        let next = this.head.next;
        size++;
        while (next !== null) {
            next = next.next;
            size++;
        }
        return size;
    },

    get: function(index) {
        if (this.head === null) {
            throw "list is empty";
        } 

        if (index === 0) {
            return this.head.data;
        }

        let size = 0;
        let next = this.head;
        while (next !== null) {
            next = next.next;
            size++;
            if (size == index) {
                return next.data;
            }
        }

        throw "list size is less than index";
    }
}

2.2 函数式声明

function UserList() {
    this.head = null;
    this.add = function(data) {
        let node = {
            data: data,
            next: null
        }
        if (this.head === null) {
            this.head = node
        } else {
            let pre = this.head;
            let next = this.head.next;
            while (next !== null) {
                pre = next;
                next = next.next;
            }
            pre.next = node;
        }
    }
    
    this.remove = function() {
        if (this.head === null || this.head.next === null) {
            this.head = null;
            return;
        }

        let pre = this.head;
        let next = this.head.next;
        while (next.next !== null) {
            pre = next;
            next = pre.next;
        }
        console.log(pre.data);
        pre.next = null;
    }

    this.isEmpty = function() {
        return this.head === null;
    }

    this.size = function() {
        if (this.head === null) {
            return 0;
        } 
        let size = 0;
        let next = this.head.next;
        size++;
        while (next !== null) {
            next = next.next;
            size++;
        }
        return size;
    }

    this.get = function() {
        if (this.head === null) {
            throw "list is empty";
        } 

        if (index === 0) {
            return this.head.data;
        }

        let size = 0;
        let next = this.head;
        while (next !== null) {
            next = next.next;
            size++;
            if (size == index) {
                return next.data;
            }
        }

        throw "list size is less than index";
    }
}

2.3 ES2015(ES6) 声明(建议)

class UserList {
    head = null;
    constructor() {

    }
    add(data) {
        let node = {
            data: data,
            next: null
        }
        if (this.head === null) {
            this.head = node
        } else {
            let pre = this.head;
            let next = this.head.next;
            while (next !== null) {
                pre = next;
                next = next.next;
            }
            pre.next = node;
        }
    }
    
    remove() {
        if (this.head === null || this.head.next === null) {
            this.head = null;
            return;
        }

        let pre = this.head;
        let next = this.head.next;
        while (next.next !== null) {
            pre = next;
            next = pre.next;
        }
        console.log(pre.data);
        pre.next = null;
    }

    isEmpty() {
        return this.head === null;
    }

    size() {
        if (this.head === null) {
            return 0;
        } 
        let size = 0;
        let next = this.head.next;
        size++;
        while (next !== null) {
            next = next.next;
            size++;
        }
        return size;
    }

    get(index) {
        if (this.head === null) {
            throw "list is empty";
        } 

        if (index === 0) {
            return this.head.data;
        }

        let size = 0;
        let next = this.head;
        while (next !== null) {
            next = next.next;
            size++;
            if (size == index) {
                return next.data;
            }
        }

        throw "list size is less than index";
    }
}