---List of javascript data structures and algorithms

---List of javascript data structures and algorithms

in daily life, people often want to use the list, for example, we have to go shopping at times, in order to buy everything when shopping, we can go before, the list of things to buy, this will be used in the lists, or when we were young school that period of time, after each test, The school will list the top 10 students of the test scores and transcripts, etc. We also use lists in our computers, so where is the list suitable for use? Not suitable for use in what place?

suitable for use in : When the list of elements is not a lot of cases, you can use the list, because the list of elements in the search or sorting, the efficiency is very high, and vice versa: If the list of elements in a very large number of cases, it is not appropriate to use the list.

One: Abstract data type definition for a list

To design an abstract data type for a list, we need to define the list, including what attributes the list should have, what actions should be performed on the list, and so on.

A list is an ordered set of data. The data items in each list are called elements. In JavaScript, the elements in a list can be any data type. How many elements can be saved in a list without prior agreement. However, the number of elements in actual use is limited by program memory.

Now that we want to design a list, we can think about implementing a list, what properties and methods they should include, and of course, the design below is based on the demo on the "JavaScript data structure and algorithms" book, so we can learn to do it later if we write the program How to design our own abstract class as a reference, we now learn the book on the demo is the most important to learn their design ideas and the way to write code. They have the following attributes;

1. Listsize (attribute): Use a listsize variable to save the number of elements in the list.

2. POS (properties): The current position of the list, the index of the element.

3. DataStore (attribute): Initializes an empty array to hold the number of elements. If we want to get a specific list of elements can use the above POS attribute; Datastore[pos];

All the methods are explained in the following list, not introduced.

listsize (attributes)	Number of elements in the list
POS (properties)	The current position of the list is the first number
DataStore (attributes)	Initializes an empty array to hold the list elements
Append (method)	Add an element to the end of the list
Remove (method)	Remove an element from the list
Find (method)	Find an element in a list returns an index
Length (method)	Returns the number of elements in a list
ToString (method)	Display elements in a list
Insert (method)	Inserts an element after the specified element
Clear (method)	Empty all the elements in the list
Contains (method)	Determines whether the given element is in the list
Front (method)	Moves the current element in a list to the first position
End (method)	Moves the current element in the list to the last position
Prev (method)	Move the current position back one
Next (method)	Move the current position forward one
CurPos (method)	Returns the current position of the list
MoveTo (method)	Moves the current position to the specified position
GetElement (method)	Returns the element at the current position

Second: How to implement the List class.

Based on the list of abstract data types defined above, we can implement a list class as follows by constructor + prototype mode.

functionList () {//number of elements in the list     This. listsize = 0; //the current position of the list is the first number     This. pos = 0; //Initializes an empty array to hold the list elements     This. DataStore = [];} List.prototype= {        //add an element to the end of the listAppendfunction(Element) {varSelf = This; self.datastore[ This. listsize++] =element; },    //remove an element from the listRemovefunction(Element) {varSelf = This; varCurindex =Self.find (Element); if(Curindex >-1) {Self.dataStore.splice (Curindex,1); --self.listsize; return true; }        return false; },    //find an element in a list returns an indexFindfunction(Element) {varSelf = This;  for(vari = 0,datalen = Self.dataStore.length; i < Datalen; i++) {            if(Self.datastore[i] = =Element) {                returni; }        }        return-1; },        //returns the number of elements in a listLengthfunction() {        return  This. listsize; },    //display elements in a listTostring:function(){        return  This. DataStore; },    /** Insert an element after the specified element * @param element Current elements * @param elementafter inserts the current element behind this element*/Insert:function(element,elementafter) {varSelf = This; varInsertpos =Self.find (Elementafter); if(Insertpos >-1) {Self.dataStore.splice (Insertpos+1,0, Element); ++self.listsize; return true; }        return false; },        //empty all the elements in the listClearfunction() {        Delete  This. DataStore;  This. DataStore = [];  This. Listsize = This. pos = 0; },    //determines whether the given element is in the listContainsfunction(Element) {varSelf = This;  for(vari = 0,ilen = Self.dataStore.length; i < Ilen; i++) {            if(Self.datastore[i] = =Element) {                return true; }        }        return false; },    //moves the current element in a list to the first positionFrontfunction(){         This. pos = 0; },    //moves the current element in the list to the last positionEndfunction(){         This. pos = This. listSize-1; },    //move the current position back onePrevfunction(){        if( This. pos > 0) {            -- This. Pos; }    },    //move the current position forward oneNextfunction(){        if( This. POS < This. listSize-1) {            ++ This. Pos; }    },    //returns the current position of the listCurPos:function(){        return  This. Pos; },    //moves the current position to the specified positionMoveTo:function(n) { This. pos =N; },    //returns the element at the current positionGetElement:function(){        return  This. datastore[ This. Pos]; }};

As above: the implementation of a list of classes, including the above so many methods, of course, we can also extend some other methods to enrich the implementation of the list class, the most important to learn as the encoding method.

---List of javascript data structures and algorithms