今年的上半年，项目原因大部分时间在写js，这期间把easyui，echarts，bootstrap都用了点皮毛，写的多了，自然也多了些感觉，不过仅局限于运用层面，于是决定再系统的看些javascript方面的书，强化运用能力，便有了这本~来自于国内知名公司前端工程师翻译自国外的书，见名知意用Javascript角度来讲数据结构和算法，一方面可以把javascript的基础知识加强，一方面加深数据结构以及算法的理解和应用。
全书篇幅不长，第一章简明扼要对javascript做了简单的介绍，基本语法、运算符、流程控制方面的基础知识，中间按章节依次对常用数据结构进行讲解。javascript除提供原生态的数组外，其他数据结构都需要自己实现，没有高级语言c#，java来的这么方便。常用数据结构分别是列表，栈，队列，链表，字典，散列，集合，二叉树，图，最后三章是算法相关，分别是排序算法、检索算法、以及两个高级算法，动态规划和贪心算法。
本书循序渐进，层层深入，从最基础的列表开始，到栈、队列，链表、hashtable、set、tree等的实现结合代码通俗易懂的呈现出来， 并结合一些实例加强对数据结构的理解。
在看完数据结构部分章节后，并动手将书中的示例敲了一遍加深印象，与此同时还有额外的收获，对js中的this关键字有了更进一步的理解。重温了一遍数据结构在js中的实现，特别是hashtable章节，对散列过程中的碰撞做了很详细的说明，如何避免碰撞的产生和提升性能方面都给出了解决方案，为今后编写高质量代码和优化代码提供了一定的借鉴作用。
列表
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>Javascript-List</title>
</head>
<body>
<script type="text/javascript">
function List(){
this.listSize=0;
this.pos=0;
this.dataStore=[];
this.clear=clear;
this.find=find;
this.toString=toString;
this.insert=insert;
this.append=append;
this.remove=remove;
this.front=front;
this.end=end;
this.prev=prev;
this.next=next;
this.length=length;
this.currPos=currPos;
this.moveTo=moveTo;
this.contains=contains;
this.getElement=getElement;
}
function append(element){
this.dataStore[this.listSize++]=element;
}
function find(element){
for(var i=0;i<this.dataStore.length;i++){
if(this.dataStore[i]==element){
return i;
}
}
return -1;
}
function remove(element){
var foundAt=this.find(element);
if(foundAt>-1){
this.dataStore.splice(foundAt,1);
--this.listSize;
return true;
}
return false;
}
function length(){
return this.listSize;
}
function toString(){
return this.dataStore;
}
function clear(){
delete this.dataStore;
this.dataStore=[];
this.listSize=this.pos=0;
}
function insert(element,after){
var insertPos=this.find(after);
if(insertPos>-1){
this.dataStore.splice(insertPos+1,0,element);
++this.listSize;
return true;
}
return false;
}
function front(){
this.pos=0;
}
function end(){
this.pos=this.listSize-1;
}
function prev(){
if(this.pos>0){
--this.pos;
}
}
function next(){
if(this.pos<this.listSize-1){
++this.pos;
}
}
function currPos(){
return this.pos;
}
function contains(element){
for(var i=0;i<this.dataStore.length;i++){
if(this.dataStore[i]==element){
return true;
}
}
return false;
}
function getElement(){
return this.dataStore[this.pos];
}
var names=new List();
names.append("123");
names.append("456");
names.append(1);
names.append("789");
console.log(names.toString());
names.front();
names.next();
names.next();
console.log(names.getElement());
</script>
</body>
</html>
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栈
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>Javascript-Stack</title>
</head>
<body>
<script type="text/javascript">
function Stack(){
this.dataStore=[];
this.top=0;
this.push=push;
this.pop=pop;
this.peek=peek;
this.length=length;
}
function push(element){
this.dataStore[this.top++]=element;
}
function pop(){
return this.dataStore[--this.top];
}
function peek(){
return this.dataStore[this.top-1];
}
function length(){
return this.top;
}
function clear(){
this.top=0;
}
var s=new Stack();
s.push("1");
s.push("2");
console.log(s.length());
console.log(s.pop());
console.log(s.length());
s.push("3");
console.log(s.length());
console.log(s.peek());
s.pop();
console.log(s.peek());
function isPalindrome(word){
var s=new Stack();
for(var i=0;i<word.length;i++){
s.push(word[i]);
}
var rword="";
while(s.length()>0){
rword+=s.pop();
}
if(word==rword){
return true;
}else{
return false;
}
}
var word="hello";
console.log(word +" is palindrome : "+isPalindrome(word));
word="level";
console.log(word +" is palindrome : "+isPalindrome(word));
word="racecar";
console.log(word +" is palindrome : "+isPalindrome(word));
</script>
</body>
</html>
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队列
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>Javascript-Queue</title>
</head>
<body>
<script type="text/javascript">
function Queue(){
this.dataStore=[];
this.enqueue=enqueue;
this.dequeue=dequeue;
this.front=front;
this.back=back;
this.toString=toString;
this.empty=empty;
}
function enqueue(element){
this.dataStore.push(element);
}
function dequeue(){
return this.dataStore.shift();
}
function front(){
return this.dataStore[0];
}
function back(){
return this.dataStore[this.dataStore.length-1];
}
function toString(){
var reStr="";
for(var i=0;i<this.dataStore.length;i++){
reStr+=this.dataStore[i]+"\n";
}
return reStr;
}
function empty(){
if(this.dataStore.length==0){
return true;
}else{
return false;
}
}
var q=new Queue();
q.enqueue("1");
q.enqueue("2");
q.enqueue("3");
console.log(q.toString());
q.dequeue();
console.log(q.toString());
console.log("front:"+q.front());
console.log("back:"+q.back());
</script>
</body>
</html>
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链表
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>javascript-linkList</title>
</head>
<body>
<script type="text/javascript">
function Node(element){
this.element=element;
this.next=null;
}
function LList(){
this.head=new Node("head");
this.find=find;
this.insert=insert;
this.remove=remove;
this.display=display;
this.findPrevious=findPrevious;
}
function find(item){
var currNode=this.head;
while(currNode.element!=item){
currNode=currNode.next;
}
return currNode;
}
function insert(newElement,item){
var newNode=new Node(newElement);
var current=this.find(item);
newNode.next=current.next;
current.next=newNode;
}
function display(){
var currNode=this.head;
while(!(currNode.next==null)){
console.log(currNode.next.element);
currNode=currNode.next;
}
}
function findPrevious(item){
var currNode=this.head;
while(!(currNode.next==null)&&
(currNode.next.element!=item)){
currNode=currNode.next;
}
return currNode;
}
function remove(item){
var preNode=this.findPrevious(item);
if(!(preNode.next==null)){
preNode.next=preNode.next.next;
}
}
var cities=new LList();
cities.insert("beijing","head");
cities.insert("shanghai","beijing");
cities.insert("shenzhen","shanghai");
cities.display();
cities.remove("shanghai");
cities.display();
</script>
</body>
</html>
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Hashtable
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>javascript-hashtable</title>
</head>
<body>
<script type="text/javascript">
function Hashtable(){
this.table=new Array(137);
this.simpleHash=simpleHash;
this.betterHash=betterHash;
this.showStorage=showStorage;
this.put=put;
}
function put(data){
//var pos=this.simpleHash(data);
var pos=this.betterHash(data);
this.table[pos]=data;
}
function simpleHash(data){
var total=0;
for(var i=0;i<data.length;i++){
total+=data.charCodeAt(i);
}
//console.log(data+":"+total);
return total%this.table.length;
}
function showStorage(){
var n=0;
for(var i=0;i<this.table.length;i++){
if(this.table[i]!=undefined){
console.log(i+": "+this.table[i]);
}
}
}
function betterHash(data){
const H=37;
var total=0;
for(var i=0;i<data.length;i++){
total+=H*total+data.charCodeAt(i);
}
total=total%this.table.length;
//console.log(total);
if(total<0){
total+=this.table.length-1;
}
return parseInt(total);
}
var someNames = ["David", "Jennifer", "Donnie", "Raymond","Cynthia", "Mike", "Clayton", "Danny", "Jonathan"];
var hTable = new Hashtable();
for (var i = 0; i < someNames.length; ++i) {
//console.log(someNames[i]+":"+someNames[i].charCodeAt(i));
hTable.put(someNames[i]);
}
hTable.showStorage();
</script>
</body>
</html>
View Code
集合
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>javascript-set</title>
</head>
<body>
<script type="text/javascript">
function Set() {
this.dataStore = [];
this.add = add;
this.remove = remove;
this.size=size;
this.union=union;
this.intersect=intersect;
this.subset = subset;
this.contains = contains;
this.difference=difference;
this.show = show;
}
function add(data) {
if (this.dataStore.indexOf(data) < 0) {
this.dataStore.push(data);
return true;
} else {
return false;
}
}
function remove(data) {
var pos = this.dataStore.indexOf(data);
if (pos > -1) {
this.dataStore.splice(pos, 1);
return true;
} else {
return false;
}
}
function show() {
return this.dataStore;
}
function contains(data) {
if (this.dataStore.indexOf(data) > -1) {
return true;
} else {
return false;
}
}
function union(set) {
var tempSet = new Set();
for (var i = 0; i < this.dataStore.length; i++) {
tempSet.add(this.dataStore[i]);
}
for (var i = 0; i < set.dataStore.length; i++) {
if (!tempSet.contains(set.dataStore[i])) {
tempSet.dataStore.push(set.dataStore[i]);
}
}
return tempSet;
}
function intersect(set) {
var tempSet = new Set();
for (var i = 0; i < this.dataStore.length; i++) {
if (set.contains(this.dataStore[i])) {
tempSet.add(this.dataStore[i]);
}
}
return tempSet;
}
function size() {
return this.dataStore.length;
}
function subset(set) {
if (this.size() > set.size()) {
return false;
} else {
for (var i = 0; i < this.dataStore.length ; i++) {
if (!set.contains(this.dataStore[i])) {
return false;
}
}
return true;
}
}
function difference(set) {
var tempSet = new Set();
for (var i = 0; i < this.dataStore.length; ++i) {
if (!set.contains(this.dataStore[i])) {
tempSet.add(this.dataStore[i]);
}
} return tempSet;
}
//basic
//var names = new Set();
//names.add("David");
//names.add("Jennifer");
//names.add("Cynthia");
//union
var cis = new Set();
//cis.add("Mike");
//cis.add("Clayton");
//cis.add("Jennifer");
//cis.add("Raymond");
//var dmp = new Set();
//dmp.add("Raymond");
//dmp.add("Cynthia");
//dmp.add("Jonathan");
//var it = new Set();
//it = cis.union(dmp);
//console.log(it.show());
//intersect
//var cis = new Set();
//cis.add("Mike");
//cis.add("Clayton");
//cis.add("Jennifer");
//cis.add("Raymond");
//var dmp = new Set();
//dmp.add("Raymond");
//dmp.add("Cynthia");
//dmp.add("Bryan");
//var inter = cis.intersect(dmp);
//console.log(inter.show()); // 显示 Raymond
//console.log(names.show());
//names.remove("David");
//console.log(names.show());
//subset
//var it = new Set();
//it.add("Cynthia");
//it.add("Clayton");
//it.add("Jennifer");
//it.add("Danny");
//it.add("Jonathan");
//it.add("Terrill");
//it.add("Raymond");
//it.add("Mike");
//var dmp = new Set();
//dmp.add("Cynthia");
//dmp.add("Raymond");
//dmp.add("Jonathan");
//if (dmp.subset(it)) {
// console.log("DMP is a subset of IT.");
//} else {
// console.log("DMP is not a subset of IT.");
//}
//differencce
var cis = new Set();
var it = new Set();
cis.add("Clayton");
cis.add("Jennifer");
cis.add("Danny");
it.add("Bryan");
it.add("Clayton");
it.add("Jennifer");
var diff = new Set();
diff = cis.difference(it);
console.log("[" + cis.show() + "] difference [" + it.show()+ "] -> [" + diff.show() + "]");
</script>
</body>
</html>
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