js创建链表
2024-09-05 06:48:20
首先要明确,我们为什么要创建链表呢?数组的大小是固定的,从数组的起点或中间插入或移除的成本很高,因为需要移动元素。尽管JS的Array类方法可以做这些,但是情况也是这样。链表存储有序的元素集合,但不同于数组,链表中的元素在内存中并不是连续放置的。每个元素由一个存储元素本身和指向下一个元素的指针组成。
相对于传统的数组,链表的一个好处在于,添加或移除元素的时候不需要移动其他元素。然而,链表需要使用指针,因此实现链表时需要额外注意。数组的另一个细节是可以直接访问任何位置的任何元素,而要想访问链表中间的一个元素,需要从起点(表头)开始迭代到列表直到找到所需元素。
好了,闲话少叙,正式创建链表!
我们使用动态原型模式来创建一个链表。列表最后一个节点的下一个元素始终是null。
function LinkedList() {
//先创建一个节点
function Node(element) {
this.element = element;
this.next = null;
}
this.head = null;
this.length = 0; //通过对一个方法append判断就可以知道是否设置了prototype
if ((typeof this.append !== 'function') && (typeof this.append !== 'string')) {
//添加元素
LinkedList.prototype.append = function(element) {
var node = new Node(element);
var current; if (this.head == null) {
this.head = node;
} else {
current = this.head;
while (current.next != null) {
current = current.next;
}
current.next = node;
}
this.length++;
}; //插入元素,成功true,失败false
LinkedList.prototype.insert = function(position, element) {
if (position > -1 && position < this.length) {
var current = this.head;
var node = new Node(element);
var previous;
var index = 0;
if (position == 0) {
node.next = current;
this.head = node;
} else {
while (index++ < position) {
previous = current;
current = current.next;
}
node.next = current;
previous.next = node;
}
this.length++;
return true;
} else {
return false;
}
}; //根据位置删除指定元素,成功 返回元素, 失败 返回null
LinkedList.prototype.removeAt = function(position) {
if (position > -1 && position < this.length) {
var current = this.head;
var previous = null;
var index = 0; if (position == 0) {
this.head = current.next;
} else {
while (index++ < position) {
previous = current;
current = current.next;
}
previous.next = current.next;
}
this.length--;
return current.element;
} else {
return null;
}
}; //根据元素删除指定元素,成功 返回元素, 失败 返回null
LinkedList.prototype.remove = function(element) {
var index = this.indexOf(element);
return this.removeAt(index);
}; //返回给定元素的索引,如果没有则返回-1
LinkedList.prototype.indexOf = function(element) {
var current = this.head;
var index = 0;
while (current) {
if (current.element === element) {
return index;
}
current = current.next;
index++;
}
return -1;
}; LinkedList.prototype.isEmpty = function() {
return this.length === 0;
};
LinkedList.prototype.size = function() {
return this.length;
};
LinkedList.prototype.toString = function() {
var string = '';
var current = this.head;
while (current) {
string += current.element;
current = current.next;
}
return string;
};
LinkedList.prototype.getHead = function() {
return this.head;
};
}
}
链表的基本使用
var linkedList = new LinkedList();
console.log(linkedList.isEmpty());//true;
linkedList.append('huang');
linkedList.append('du')
linkedList.insert(1,'cheng');
console.log(linkedList.toString());//huangchengdu
console.log(linkedList.indexOf('du'));//
console.log(linkedList.size());//
console.log(linkedList.removeAt(2));//du
console.log(linkedList.toString());//huangcheng
创建双向链表
在双向链表中,链接是双向的:一个链向下一个元素, 另一个链向前一个元素。
双向链表和链表的区别就是有一个tail属性,所以必须重写insert、append、removeAt方法。每个节点对应的Node也多了一个prev属性。
//寄生组合式继承实现,详见javascript高级程序设计第七章
function inheritPrototype(subType, superType) {
function object(o) {
function F() {}
F.prototype = o;
return new F();
}
var prototype = object(superType.prototype);
prototype.constructor = subType;
subType.prototype = prototype;
}
function DoublyLinkedList() {
function Node(element) {
this.element = element;
this.next = null;
this.prev = null;
}
this.tail = null;
LinkedList.call(this);
//与LinkedList不同的方法自己实现。
this.insert = function(position, element) {
if (position > -1 && position <= this.length) {
var node = new Node(element);
var current = this.head;
var previous;
var index = 0;
if (position === 0) {
if (!this.head) {
this.head = node;
this.tail = node;
} else {
node.next = current;
current.prev = node;
this.head = node;
}
} else if (position == this.length) {
current = this.tail;
current.next = node;
node.prev = current;
this.tail = node;
} else {
while (index++ < position) {
previous = current;
current = current.next;
}
previous.next = node;
node.next = current;
current.prev = node;
node.prev = previous;
}
this.length++;
return true;
} else {
return false;
}
};
this.append = function(element) {
var node = new Node(element);
var current;
if (this.head === null) {
this.head = node;
this.tail = node;
} else {
current = this.head;
while (current.next !== null) {
current = current.next;
}
current.next = node;
node.prev = current;
this.tail = node;
}
this.length++;
};
this.removeAt = function(position) {
if (position > -1 && position < this.length) {
var current = this.head;
var previous;
var index = 0;
if (position === 0) {
this.head = current.next;
if (this.length === 1) {
this.tail = null;
} else {
this.head.prev = null;
}
} else if (position === (this.length - 1)) {
current = this.tail;
this.tail = current.prev;
this.tail.next = null;
} else {
while (index++ < position) {
previous = current;
current = current.next;
}
previous.next = current.next;
current.next.prev = previous;
}
this.length--;
return current.element;
} else {
return false;
}
};
}
inheritPrototype(DoublyLinkedList, LinkedList);
双向链表的基本使用
var doublyList = new DoublyLinkedList();
console.log(doublyList.isEmpty()); //true;
doublyList.append('huang');
doublyList.append('du')
doublyList.insert(1, 'cheng');
console.log(doublyList.toString()); //huangchengdu
console.log(doublyList.indexOf('du')); //
console.log(doublyList.size()); //
console.log(doublyList.removeAt(2)); //du
console.log(doublyList.toString()); //huangcheng
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