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

下面是一个队列的链表版本,它也包括最后一个节点,这是@perkins建议的,也是最合适的。

// QUEUE Object Definition

var Queue = function() {
  this.first = null;
  this.last = null;
  this.size = 0;
};

var Node = function(data) {
  this.data = data;
  this.next = null;
};

Queue.prototype.enqueue = function(data) {
  var node = new Node(data);

  if (!this.first){ // for empty list first and last are the same
    this.first = node;
    this.last = node;
  } else { // otherwise we stick it on the end
    this.last.next=node;
    this.last=node;
  }

  this.size += 1;
  return node;
};

Queue.prototype.dequeue = function() {
  if (!this.first) //check for empty list
    return null;

  temp = this.first; // grab top of list
  if (this.first==this.last) {
    this.last=null;  // when we need to pop the last one
  }
  this.first = this.first.next; // move top of list down
  this.size -= 1;
  return temp;
};

其他回答

Javascript有push和pop方法,它们操作在普通的Javascript数组对象上。

关于排队,请看这里:

http://safalra.com/web-design/javascript/queues/

Queues can be implemented in JavaScript using either the push and shift methods or unshift and pop methods of the array object. Although this is a simple way to implement queues, it is very inefficient for large queues — because of the methods operate on arrays, the shift and unshift methods move every element in the array each time they are called. Queue.js is a simple and efficient queue implementation for JavaScript whose dequeue function runs in amortized constant time. As a result, for larger queues, it can be significantly faster than using arrays.

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”

我在实现BFS时遇到了这个线程。在疑惑为何表现如此糟糕之后,我做了一些调查。array.shift()通常在O(n)中运行,这将我的BFS运行时从O(V+E)增加到O(V^2+E)。

我没有从头开始实现一个队列,而是使用了npm包双端队列,它与之前使用的数组方法兼容,工作起来很有魅力。 deque可以用作堆栈或队列。

    //import package
    import Deque from 'double-ended-queue';

    //create queue
    let queue = new Deque();
    //append
    queue.push(item);
    //dequeue (get first item inserted)
    let firstItem = queue.shift();

    //pop (get last item inserted)
    let lastItem = queue.pop();

Javascript中的常规数组结构是一个堆栈(先入后出),也可以用作队列(先入先出),这取决于你所做的调用。

检查这个链接,看看如何让一个数组像一个队列:

队列

As many have said: native array using push and pop is fine for a stack, but using shift for taking elements from a queue means that the remaining elements need to move, which is potentially slow. The idea of using two stacks to make a queue in kevinyu's answer is a nice idea to fix it, and of course that can be done with native-array-stacks as well. (Edit: there was actually already an answer by Yuki-Dreamer that does this, albeit less compactly. I didn't notice it until now because it was unfairly downvoted.)

下面是一个使用ES5/ES6特性的紧凑实现,它使队列对象的行为尽可能接近本机的push/shift变体,除了每次操作花费O(1)平摊时间:

const queue = () => {
    const a = [], b = [];
    return {
        push: (...elts) => a.push(...elts),
        shift: () => {
            if (b.length === 0) {
                while (a.length > 0) { b.push(a.pop()) }
            }
            return b.pop();
        },
        get length() { return a.length + b.length }
    }
}

现在你可以做:

const q = queue();
q.push(8);
q.push(9);
q.push(10);
console.log(q.length);          // outputs 3
console.log(q.shift());         // outputs 8
q.push(11);
console.log(q.shift());         // outputs 9
console.log(q.shift());         // outputs 10
console.log(q.shift());         // outputs 11
console.log(q.shift());         // outputs undefined

队列实现对长度使用getter语法,使其看起来像一个属性,并对push使用rest参数语法,以允许一次推送多个内容。如果你不想这样做,你可以用push: elt => a.push(elt),替换第4行。(但是请注意,你不能用push: a.push替换它,就像我自己第一次尝试的那样,结果非常奇怪:这是因为它导致本机push方法被调用,并设置为队列对象。)