在JavaScript中实现堆栈和队列的最佳方法是什么?

我想做调车场算法我需要这些数据结构。


当前回答

如果你理解栈的push()和pop()函数,那么queue只是在相反的意义上进行这些操作之一。push()的对边是unshift(), pop()的对边是shift()。 然后:

//classic stack
var stack = [];
stack.push("first"); // push inserts at the end
stack.push("second");
stack.push("last");
stack.pop(); //pop takes the "last" element

//One way to implement queue is to insert elements in the oposite sense than a stack
var queue = [];
queue.unshift("first"); //unshift inserts at the beginning
queue.unshift("second");
queue.unshift("last");
queue.pop(); //"first"

//other way to do queues is to take the elements in the oposite sense than stack
var queue = [];
queue.push("first"); //push, as in the stack inserts at the end
queue.push("second");
queue.push("last");
queue.shift(); //but shift takes the "first" element

其他回答

使用两个堆栈构造一个队列。

O(1)用于入队和出队操作。

class Queue {
  constructor() {
    this.s1 = []; // in
    this.s2 = []; // out
  }

  enqueue(val) {
    this.s1.push(val);
  }

  dequeue() {
    if (this.s2.length === 0) {
      this._move();
    }

    return this.s2.pop(); // return undefined if empty
  }

  _move() {
    while (this.s1.length) {
      this.s2.push(this.s1.pop());
    }
  }
}
var stack = [];
stack.push(2);       // stack is now [2]
stack.push(5);       // stack is now [2, 5]
var i = stack.pop(); // stack is now [2]
alert(i);            // displays 5

var queue = [];
queue.push(2);         // queue is now [2]
queue.push(5);         // queue is now [2, 5]
var i = queue.shift(); // queue is now [5]
alert(i);              // displays 2

摘自“9个你可能不知道的JavaScript技巧”

数组。

栈:

var stack = [];

//put value on top of stack
stack.push(1);

//remove value from top of stack
var value = stack.pop();

队列:

var queue = [];

//put value on end of queue
queue.push(1);

//Take first value from queue
var value = queue.shift();

如果你正在寻找带有一些基本操作(基于链表)的堆栈和队列数据结构的ES6 OOP实现,那么它可能是这样的:

Queue.js

import LinkedList from '../linked-list/LinkedList';

export default class Queue {
  constructor() {
    this.linkedList = new LinkedList();
  }

  isEmpty() {
    return !this.linkedList.tail;
  }

  peek() {
    if (!this.linkedList.head) {
      return null;
    }

    return this.linkedList.head.value;
  }

  enqueue(value) {
    this.linkedList.append(value);
  }

  dequeue() {
    const removedHead = this.linkedList.deleteHead();
    return removedHead ? removedHead.value : null;
  }

  toString(callback) {
    return this.linkedList.toString(callback);
  }
}

Stack.js

import LinkedList from '../linked-list/LinkedList';

export default class Stack {
  constructor() {
    this.linkedList = new LinkedList();
  }

  /**
   * @return {boolean}
   */
  isEmpty() {
    return !this.linkedList.tail;
  }

  /**
   * @return {*}
   */
  peek() {
    if (!this.linkedList.tail) {
      return null;
    }

    return this.linkedList.tail.value;
  }

  /**
   * @param {*} value
   */
  push(value) {
    this.linkedList.append(value);
  }

  /**
   * @return {*}
   */
  pop() {
    const removedTail = this.linkedList.deleteTail();
    return removedTail ? removedTail.value : null;
  }

  /**
   * @return {*[]}
   */
  toArray() {
    return this.linkedList
      .toArray()
      .map(linkedListNode => linkedListNode.value)
      .reverse();
  }

  /**
   * @param {function} [callback]
   * @return {string}
   */
  toString(callback) {
    return this.linkedList.toString(callback);
  }
}

上面例子中用于堆栈和队列的LinkedList实现可以在GitHub上找到。

下面是一个相当简单的队列实现,有两个目标:

与array.shift()不同,您知道这个出队列方法需要常数时间(O(1))。 为了提高速度,这种方法使用的分配比链表方法少得多。

堆栈实现只共享第二个目标。

// Queue
function Queue() {
        this.q = new Array(5);
        this.first = 0;
        this.size = 0;
}
Queue.prototype.enqueue = function(a) {
        var other;
        if (this.size == this.q.length) {
                other = new Array(this.size*2);
                for (var i = 0; i < this.size; i++) {
                        other[i] = this.q[(this.first+i)%this.size];
                }
                this.first = 0;
                this.q = other;
        }
        this.q[(this.first+this.size)%this.q.length] = a;
        this.size++;
};
Queue.prototype.dequeue = function() {
        if (this.size == 0) return undefined;
        this.size--;
        var ret = this.q[this.first];
        this.first = (this.first+1)%this.q.length;
        return ret;
};
Queue.prototype.peek = function() { return this.size > 0 ? this.q[this.first] : undefined; };
Queue.prototype.isEmpty = function() { return this.size == 0; };

// Stack
function Stack() {
        this.s = new Array(5);
        this.size = 0;
}
Stack.prototype.push = function(a) {
        var other;
    if (this.size == this.s.length) {
            other = new Array(this.s.length*2);
            for (var i = 0; i < this.s.length; i++) other[i] = this.s[i];
            this.s = other;
    }
    this.s[this.size++] = a;
};
Stack.prototype.pop = function() {
        if (this.size == 0) return undefined;
        return this.s[--this.size];
};
Stack.prototype.peek = function() { return this.size > 0 ? this.s[this.size-1] : undefined; };