链表 -- 大二上第十周

目录

链表

链表的封装

function LinkList() {
    // 内部的类:节点类
    function Node(data) {
        this.data = data;
        this.next = null;
    }
    
    this.head = null;
    this.length = 0;

    LinkList.prototype.append = function (data) {
        var newNode = new Node(data);

        if (this.length == 0) {
            this.head = newNode;
        }else{
            var current = this.head;
            while(current.next){
                current = current.next;
            }
            current.next = newNode;
        }
        this.length += 1;
    }

    LinkList.prototype.toString = function () {
        var current = this.head;
        var listString = '';

        while(current){
            listString += current.data + ' ';
            current = current.next;
        }
        return listString;
    }

    LinkList.prototype.insert = function (position, data) {
        if ( position < 0 || position > this.length) return false;

        var newNode = new Node(data);
        if (position == 0) {
            newNode.next = this.head;
            this.head = newNode;
        }else{
            var index = 0;
            var current = this.head;
            var previous = null;
            // while(index ++ < position){
            //     previous = current;
            //     current = current.next;
            // }
            // newNode.next = current;
            // previous.next = newNode;
            while(index ++ < position - 1){
                current = current.next; 
            }
            newNode.next = current.next;
            current.next = newNode;
            // 上下两种是一样的
        }

        this.length += 1
        return true;
    }
    LinkList.prototype.get = function (position) {
        if (position < 0 || position >= this.length) return null;

        var current =this.head;
        var index = 0;
        while(index++ < position){
            current = current.next;
        }
        return current.data;
    }

    LinkList.prototype.indexOf = function (data) {//返回元素在列表中的索引,没有返回-1
            var current = this.head;
            var index = 0;
            while(current){
                index ++;
            if (current.data == data) {
                return index;
            }
            current = current.next;
            }
            return -1;
    }

    LinkList.prototype.upDate = function (position, data) {//修改某个位置的元素
        var current = this.head;
        var index = 0;

        if (position < 0 || position >= this.length) return false;
        while(index ++ < position){
            current = current.next;
        }
        current.data = data;

        return true;
    }

    LinkList.prototype.removeAt = function (position) {//移除指定位置的元素结点
        var current = this.head;
        var pre;
        var index = 0;

        if (position < 0 || position >= this.length) return null;
        if (position == 0) {
            this.head = this.head.next;
        }else{
            while(index++ < position){
                pre = current;
                current = current.next;
            }
            pre.next = current.next;
        } 
        this.length -= 1;
        return current.data;
    }

    LinkList.prototype.remove = function (element) {//移除确定元素的结点
        // var position = this.indexOf(element) - 1;

        // this.removeAt(position);
        
        var current = this.head;
        var pre = null;
        
        for(var i = 0; i < this.length; i++){
            if (current.data == element) {
                if (current == this.head) {
                    this.head = this.head.next;
                }else{
                    pre.next = current.next;
                }
                break;
            }
            pre = current;
            current = current.next;
        }
        this.length -= 1;

        // 两种办法都可以
    }

    LinkList.prototype.isEmpty = function () {
        return this.length == 0;
    }

    LinkList.prototype.size = function () {
        return this.length;
    }
}

链表 -- 大二上第十周

双向链表

是既可以从头遍历到尾,又可以从尾遍历到头
一个节点既有向前连接的引用,也有向后连接的引用
小缺点:再每次插入或删除节点的时候,要处理四个引用

function DoublyLinked() {
    function Node(data) {
        this.data = data;
        this.prev = null;
        this.next = null;
    }
    this.head = null;
    this.tail = null;
    this.length = 0;
    
    DoublyLinked.prototype.append = function (data) {
        let newNode = new Node(data);
        if (!this.head) {
            this.head = newNode;
            this.tail = newNode;
        }else{
            newNode.prev = this.tail;
            this.tail.next = newNode;
            this.tail = newNode;
        }
        this.length ++;
    }
    DoublyLinked.prototype.insert = function (position, element) {
        let newNode = new Node(element);
        let current = this.head;
        let index = 0;

        if (position < 0 || position > this.length) return false;
        
        if (this.length == 0) {
            this.head = newNode;
            this.tail = newNode;
        }else{//有三种情况,主要还是既有head还有tail
            if (position == 0) {
                this.head.prev = newNode;
                newNode.next = this.head;
                this.head = newNode;
            }else if (this.length == position) {
                newNode.prev = this.tail;
                this.tail.next = newNode;
                this.tail = newNode;
            }else{
                while(index ++ < position){
                    current = current.next;
                }//其实是插在current的前面
                current.prev.next = newNode;
                newNode.next = current;
                newNode.prev = current.prev;
                current.prev = newNode;
            }
        }
    
        this.length ++;
        return true;
    }
    DoublyLinked.prototype.get = function (position) {
        let current = this.head;
        let index = 0;
        if (position < 0 || position >= this.length) return null;
        while(index++ < position){
            current = current.next;
        }
        return current.data;
    }
    DoublyLinked.prototype.indexOf = function (element) {
        let current = this.head;
        
        for (let i = 0; i < this.length; i++) {
            if (current.data == element) {
                return i;
            }
            current = current.next;
        }
        return -1;
    }
    DoublyLinked.prototype.upDate = function (position, element) {//修改这个地方的data
        let index = 0;
        if (position < 0 || position >= this.length) return false;
        if (position < this.length/2) {//这里是循环的优化,减少时间复杂度,get方法也可以用
            let current = this.head;
            while(index ++ < position){
                current = current.next;
            }
            current.data = element;
        }else{
            let current = this.tail;
            index = this.length - 1;
            while(index-- > position){
                current = current.prev;
            }
            current.data = element;
        }
    }
    DoublyLinked.prototype.removeAt = function (position) {
        if (position < 0 || position >= this.length) return false;

        let current = this.head;
        let index = 0;

        if(this.length == 1){
            this.head = null;
            this.tail = null;
        }else {
            if (position == 0) {
                this.head = this.head.next;
                this.head.prev = null;
            }else if (position == this.length - 1) {
                current = this.tail;
                this.tail = this.tail.prev;
                this.tail.next = null;
            }else{
                while(index ++ < position){
                    current = current.next; 
                }
                current.next.prev = current.prev;
                current.prev.next = current.next;
            }
        }

        this.length --;

        return current.data;
    }
    DoublyLinked.prototype.remove = function (element) {
        let index = this.indexOf(element);

        return this.removeAt(index);
    }
    DoublyLinked.prototype.toString = function () {
        return this.backwardString();
    }
    DoublyLinked.prototype.forwardString = function () {
        let current = this.tail;
        let resstr = '';
        while(current){
            resstr += current.data + ' ';
            current = current.prev;
        }
        return resstr;
    }
    DoublyLinked.prototype.backwardString = function () {
        let current = this.head;
        let resstr = '';
        while(current){
            resstr += current.data + ' ';
            current = current.next;
        }
        return resstr;
    }
    DoublyLinked.prototype.isEmpty = function () {
        return this.length == 0;
    }
    DoublyLinked.prototype.size = function () {
        return this.length;
    }
    DoublyLinked.prototype.getHead = function () {
        return this.head;
    }
    DoublyLinked.prototype.getTail = function () {
        return this.tail;
    }
}

链表 -- 大二上第十周

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