JavaScript(7) - 栈和队列

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栈

stack.js文件如下：

function Stack(){    var items = [];    //入栈    this.push = function(element){        items.push(element);    }    //出栈    this.pop = function(){        return items.pop();    }    //返回栈顶元素    this.peek = function(){        return items[items.length - 1];    }    //是否为空    this.isEmpty = function(){        return items.length === 0;    }    //栈元素个数    this.size = function(){        return items.length;    }    //清空栈    this.clear = function(){        items = [];    }    //打印元素    this.print = function(){        console.log(items.toString());    }}module.exports = Stack;

利用栈实现从十进制转换为十六进制以内任意进制，代码如下(在node环境下运行)：

var Stack = require('./stack');var newStack = new Stack();//newStack.push('Aaa');//newStack.push('Bbb');//newStack.print();function baseConverter(decNumber, base){    var remStack = new Stack(),        rem,                                //记录余数        baseString = '',                    //记录转换后的字符串        digits = '0123456789ABCDEF';        //用来查找对应的字符    while(decNumber > 0){        rem = decNumber % base;        //console.log(rem);        remStack.push(rem);        //remStack.print();        decNumber = Math.floor(decNumber / base);    }    while(!remStack.isEmpty()){        baseString += digits[remStack.pop()];    }    return baseString;}console.log(baseConverter(100345, 2));      //11000011111111001console.log(baseConverter(100345, 8));      //303771console.log(baseConverter(100345, 16));     //187F9

队列

队列遵循FIFO（First In First Out，先进先出，也称为先来先服务）原则的一组有序的项。
队列在尾部添加新元素，并从顶部移除元素。最新添加的元素必须排在队列的末尾。
队列的实现：

function Queue() {    var items = [];    this.enqueue = function(element){        items.push(element);    };    this.dequeue = function(){        return items.shift();    };    this.front = function(){        return items[0];    };    this.isEmpty = function(){        return items.length == 0;    };    this.clear = function(){        items = [];    };    this.size = function(){        return items.length;    };    this.print = function(){        console.log(items.toString());    };}

举个例子，如何使用队列：

var queue = new Queue();console.log(queue.isEmpty());   //outputs truequeue.enqueue("John");queue.enqueue("Jack");queue.print();                  //John,Jackqueue.enqueue("Camila");queue.print();                  //John,Jack,Camilaconsole.log(queue.size());      //outputs 3console.log(queue.isEmpty());   //outputs falsequeue.dequeue();console.log(queue.dequeue());   //Jackqueue.print();                  //Camila

优先级队列

function PriorityQueue() {    var items = [];    function QueueElement (element, priority){        this.element = element;        this.priority = priority;    }    this.enqueue = function(element, priority){        var queueElement = new QueueElement(element, priority);        if (this.isEmpty()){            items.push(queueElement);        } else {            var added = false;            for (var i=0; i<items.length; i++){                if (queueElement.priority < items[i].priority){                    items.splice(i,0,queueElement);                    added = true;                    break;                }            }            if (!added){                items.push(queueElement);            }        }    };    this.dequeue = function(){        return items.shift();    };    this.front = function(){        return items[0];    };    this.isEmpty = function(){        return items.length == 0;    };    this.size = function(){        return items.length;    };    this. print = function(){        for (var i=0; i<items.length; i++){            console.log(items[i].element + ' - ' + items[i].priority);        }    };}var priorityQueue = new PriorityQueue();priorityQueue.enqueue("John", 2);priorityQueue.enqueue("Jack", 1);priorityQueue.enqueue("Camila", 1);priorityQueue.enqueue("Maxwell", 2);priorityQueue.enqueue("Ana", 3);priorityQueue.print();//Jack - 1,Camila - 1,John - 2,Maxwell - 2,Ana - 3

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