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。
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
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。)
其他回答
如果你想创建自己的数据结构,你可以创建自己的:
var Stack = function(){
this.top = null;
this.size = 0;
};
var Node = function(data){
this.data = data;
this.previous = null;
};
Stack.prototype.push = function(data) {
var node = new Node(data);
node.previous = this.top;
this.top = node;
this.size += 1;
return this.top;
};
Stack.prototype.pop = function() {
temp = this.top;
this.top = this.top.previous;
this.size -= 1;
return temp;
};
对于队列:
var Queue = function() {
this.first = 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){
this.first = node;
} else {
n = this.first;
while (n.next) {
n = n.next;
}
n.next = node;
}
this.size += 1;
return node;
};
Queue.prototype.dequeue = function() {
temp = this.first;
this.first = this.first.next;
this.size -= 1;
return temp;
};
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.
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。)
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;
};
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”