前端算法排序之两个栈实现队列

• 利用2个栈实现一个队列, 只需要实现先进先出的功能
• @constructor

var Stack = require('https://21cm.js.org/lib/stack');
var Queue = function () {
    this.stack1 = new Stack();
    this.stack2 = new Stack();
}

Queue.prototype.enqueue = function (ele) {
    this.stack1.push(ele);   //入队操作都压入栈1
}

Queue.prototype.dequeue = function () {
    if (this.stack2.length()) {  //栈2不空,直接pop
        return this.stack2.pop();
    } else {  //若第二个栈不空,则将第一个栈中的所有元素出栈并压入栈2,并pop一次
        while (this.stack1.length()) {
            this.stack2.push(this.stack1.pop());
        }
        return this.stack2.pop();
    }
}

var q = new Queue();
q.enqueue(1);
q.enqueue(2);
q.enqueue(3);

console.log(q.dequeue());
console.log(q.dequeue());
console.log(q.stack1);
console.log(q.stack2);

console.log('----------------------------');

q.enqueue(4);
q.enqueue(5);
console.log(q.dequeue());
console.log(q.stack1);
console.log(q.stack2);

console.log('----------------------------');

console.log(q.dequeue());
console.log(q.dequeue());
console.log(q.stack1);
console.log(q.stack2);

console.log('----------------------------');