Day 2: Trying to Create Class in JavaScript

[githubdudu]

I'll be working on today's study material soon. Sorry for the delay.

Review of Day 1

Some useful reading materials:

1. Value type and reference type: The Golden Rule of Equals  https://joshhug.gitbooks.io/hug61b/content/chap2/chap21.html

2. How to implement SLL and DLL :
   https://joshhug.gitbooks.io/hug61b/content/chap2/chap22.html
   https://www.geeksforgeeks.org/singly-linked-list-tutorial/

3. Time complexity: https://joshhug.gitbooks.io/hug61b/content/chap8/chap84.html

   

   

Some explaination

The performance of software matters.

Big O or Big omega is just a tool for evaluating the algorithm or data structure. After we implement the SLL and DLL, we will summary the time complexity of each operations.

Java version DLL. The Node class and type can be used in the Node class itself.

[githubdudu]

Task of Day2

Today, we will implement the DLL class. Both in Java and JS.

Let's continue with the topic of performance. To answer the question -- is DLL useful? We will use Big O notation to compare DLL with ArrayList. Here, the 'ArrayList' refers to the data structure 'ArrayList' in Java, where elements can be accessed by their index and positions. 'ArrayList' is also called sequence or just 'list'. In JavaScript, array works similarly to 'ArrayList' in Java.

We already knew that 'DLL' and 'ArrayList' have same API /method in Java. (In Java, the implementation of DLL is LinkedList class.). The only difference of them for users is their performances.

We will create our own version of DLL in three steps:

1. Define the API
2. Write the code
3. Evaluation them via Big O

Define the API

public interface List {
    //Inserts the specified element at the specified position
    void add(int index, int value);
    //Inserts the specified element at the beginning of this list
    void addFirst(int value);
    //Appends the specified element to the end of this list
    void addLast(int value);
    
    //Returns the element at the specified position in this list
    int get(int index);
    //Returns the first element in this list
    int getFirst();
    //Returns the last element in this list
    int getLast();

    // Removes the element at the specified position in this list, Shifts any subsequent elements to the left
    int remove(int index);
    //Removes and returns the first element from this list
    int removeFirst();
    //Removes and returns the last element from this list
    int removeLast();

    // Returns the number of elements in this list
    int size();
    // Returns true if this list contains no elements
    boolean isEmpty();

    // Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element
    int indexOf(int value);
    // Returns true if this list contains the specified element
    boolean contains(int value);
}

Write your code

TASK1 :
Template has provided in this repo. https://github.com/githubdudu/react-study-group/blob/master/day2/java/DLL.java
Please git clone and exercise yourself. Helper method to convert an array to a DLL has been provided. And some basic test case provided.

You don't need to consider the exception case. Just assume that all input and parameters are valid.
If there is any bug or error, please modify it as you wish. I haven't tested it thoroughly.

TASK2:
The first version of DLL only supports saving integers. Try implement a second version of DLL2 that implements interface "LIST2" https://github.com/githubdudu/react-study-group/blob/master/day2/java/List2.java

TASK3:
Try the Javascript version of DDL. https://github.com/githubdudu/react-study-group/blob/master/day2/javascript/dll.js

You can reply with your code below. If you wish, you may also push your branch of code to this repo.
@tiff777 @Karson421 @zep @chris @andred @katie

I think today's workload is already high enough. Let's leave the rest of the exercises and evaluation part tomorrow.

[githubdudu]

Tomorrow:

• Combine two DLL.

• JS function feature.

• JS prototype and inheritance.

• The advantage of DLL.

• Iterator in JS

• Object and valid key name.

• valid function name

• implement iterator

Further study plan:

• Create a react project.
• Tic-tac-toe practice on React official website.
• what is babel and how it work. what is JSX
• what is component, life cycle of component
• Closure (JS)
• functional programming
• Calculator project
• difference of the scope of variable in JS
• Where to save data on Frontend? Windows, Root, Session Storage
• the render process of browser / client

[githubdudu]

Sorry there was bug. Already fixed. Please fetch latest commits

[tiff777]

Thanks for creating the exercise. o7
I have pushed the code to my branch.

[jinwookuk]

I don't have permission to publish my own branch, so I completed these tasks on a fork!
I'm not sure how to put this back on to a separate branch 😩

[githubdudu]

Don't worries about pushing a separate branch. Do you have a link to your fork?
Just invited you. Now you have permission.

[githubdudu]

To Jin, you DLL2 class:

    public static DLL ArrayToDLL(int[] arr) {
        DLL dll = new DLL();
        for (int i = 0; i < arr.length; i++) {
            dll.addLast(arr[i]);
        }
        return dll;
    }

    public static void main(String[] args) {
        int[] arr = { 1, 2, 3, 4, 5 };
        DLL dll = ArrayToDLL(arr);
        System.out.println(dll);

A better version should be

    public static DLL<V> ArrayToDLL(V[] arr) {
        DLL<V> dll = new DLL<>();
        for (int i = 0; i < arr.length; i++) {
            dll.addLast(arr[i]);
        }
        return dll;
    }

    public static void main(String[] args) {
        int[] arr = { 1, 2, 3, 4, 5 };
        DLL<Integer> dll = ArrayToDLL(arr);
        System.out.println(dll);

DLL2 has a generic type. It's better to specify the generic type.

[jinwookuk]

To Jin, you DLL2 class:

public static DLL ArrayToDLL(int[] arr) {
    DLL dll = new DLL();
    for (int i = 0; i < arr.length; i++) {
        dll.addLast(arr[i]);
    }
    return dll;
}

public static void main(String[] args) {
    int[] arr = { 1, 2, 3, 4, 5 };
    DLL dll = ArrayToDLL(arr);
    System.out.println(dll);

A better version should be

public static DLL<V> ArrayToDLL(V[] arr) {
    DLL<V> dll = new DLL<>();
    for (int i = 0; i < arr.length; i++) {
        dll.addLast(arr[i]);
    }
    return dll;
}

public static void main(String[] args) {
    int[] arr = { 1, 2, 3, 4, 5 };
    DLL<Integer> dll = ArrayToDLL(arr);
    System.out.println(dll);

DLL2 has a generic type. It's better to specify the generic type.

Aha! Got it! Thank you for the feedback Dewey 👍