magical indices javascript assignment expert

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• Detect a negative cycle in a Graph | (Bellman Ford)
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• Applications, Advantages and Disadvantages of Depth First Search (DFS)
• Minimize the number of weakly connected nodes
• Check if each connected component has equal number of vertices and edges
• Find ancestors of each node in the given Graph
• Check if a graphs has a cycle of odd length

Magical Indices in an array

Given an array A of integers. Index i of A is said to be connected to index j if j = (i + A[i]) % n + 1 (Assume 1-based indexing). Start traversing array from index i and jump to its next connected index. If on traversing array in the described order, index i is again visited then index i is a magical index. Count the number of magical indexes in the array. Assume that array A consists of non-negative integers.

Examples :  

Approach: The problem is of counting number of nodes in all the cycles present in the graph. Each index represents a single node of the graph. Each node has a single directed edge as described in the problem statement. This graph has a special property: On starting a traversal from any vertex, a cycle is always detected. This property will be helpful in reducing the time complexity of the solution.

Read this post on how to detect cycle in a directed graph: Detect Cycle in directed graph Let the traversal begins from node i. Node i will be called parent node of this traversal and this parent node will be assigned to all the nodes visited during traversal. While traversing the graph if we discover a node that is already visited and parent node of that visited node is same as parent node of the traversal then a new cycle is detected. To count number of nodes in this cycle, start another dfs from this node until this same node is not visited again. This procedure is repeated for every node i of the graph. In worst case every node will be traversed at most 3 times. Hence solution has linear time complexity.

The stepwise algorithm is:  

Implementation:  

Complexity Analysis:

• Time Complexity: O(n) 
• Space Complexity: O(n)  

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(solved): magical indicesgiven an array of integers and a number x. an index is valid ifitem y  ....

Magical Indices

Given an array of integers and a number

• x. An index is valid ifitem y at an index is increased by x and
• x+y would be greater than the sum of all other items in the array.

Write a JS program to determine the number of valid indices.

• The first line of input contains an array
• The second line of input contains a number
• The output should be a number indicating the number of valid positions

Explanation

For example, an array A = [10, 20, 30] and a value x = 25.

We have values 10, 20, 30 at indices 0,1,2 respectively.

• Here index 0 is invalid because
• 10 + 25 = 35 is less than 20 + 30 = 50
• Here index 1 is valid because
• 20 + 25 = 45 is greater than 10 + 30 = 40
• Here index 2 is valid because
• 30 + 25 = 55 is greater than 10 + 20 = 30

So there are 2 valid indices.

Sample Input 1

[1, 2, 3, 5, 7]

Sample Output 1

Sample Input 2

[34, 32, 37, 38, 40]

Sample Output 2

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Posted on Sep 11, 2023

JavaScript Functions(Part 3): Your Magic Spells

In our last magical seminar, we delved deep into the intricate world of JavaScript functions, learning the spells and chants that shape our world. The spell book was opened, and secrets were revealed. But like every great wizard knows, the depth of magic is vast, and our journey has just begun.

Today, we venture further into this enchanted forest of functions, unearthing more potent spells and understanding the legacy of ancient code mages.

🪄 Closures: The Enchanted Lockets

In the magical world of JavaScript, a closure is like an enchanted locket, preserving memories (variables) from disappearing even after the spell (function) has been cast.

Imagine casting a spell to create a magical barrier. This barrier remembers the strength at which you cast it and can adjust itself accordingly in the future.

The inner function, even when invoked outside its containing function, still has access to barrierStrength .

🌌 Higher-Order Functions: Conjuring Magic with Magic

In our realm, some spells can manipulate other spells to create new enchantments. These are known as higher-order functions.

For instance, let's take the ancient spell map , which can transform every item in an array.

The map spell takes another spell (function) and applies it to each item, giving us a new potion (array).

🧙‍♂️ Recursive Functions: The Magic that Calls Upon Itself

Some spells are so mighty that they call upon themselves for added power. These are our recursive functions.

Imagine a mirror that reflects another mirror, which then reflects another, creating an infinite loop of reflections.

Use recursive spells with caution, young mage. For if not controlled, they can spiral out of hand!

🌠 Conclusion: The Ever-Expanding Grimoire

The world of JavaScript functions is as expansive as the universe of magic itself. With every page turned in our spell book, we uncover more wonders, more nuances, and greater power.

As we close this chapter of our grimoire, remember: The true magic isn't just in knowing the spells, but in understanding their essence and wielding them with wisdom.

Till our next magical meet, practice these spells, and always remember the first rule of magic - respect the craft!

Sorcerer’s Assignments: Test Your Magic

🔮 1. The Enchanted Forest of Closures:

Objective: Venture deep into the world of closures and craft a spell that creates magical creatures. Each creature remembers the number of times it has been summoned.

🌌 2. Mystic Transformations with Higher-Order Spells:

Objective: Use the ancient spell filter to find all the magical artifacts that are older than a thousand years from an array.

🧙‍♂️ 3. Mirrors of Recursion:

Objective: Craft a recursive spell that counts down from a number and at the end shouts "Blast off!"

Remember, young mage: Crafting spells is not just about getting them right, but understanding the essence and rhythm within them. Once you've attempted these tasks, share your incantations in the comments. Let's see who's ready for the next level in the world of magic!

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JS Tutorial

Js versions, js functions, js html dom, js browser bom, js web apis, js vs jquery, js graphics, js examples, js references, javascript assignment, javascript assignment operators.

Assignment operators assign values to JavaScript variables.

Shift Assignment Operators

Bitwise assignment operators, logical assignment operators, the = operator.

The Simple Assignment Operator assigns a value to a variable.

Simple Assignment Examples

The += operator.

The Addition Assignment Operator adds a value to a variable.

Addition Assignment Examples

The -= operator.

The Subtraction Assignment Operator subtracts a value from a variable.

Subtraction Assignment Example

The *= operator.

The Multiplication Assignment Operator multiplies a variable.

Multiplication Assignment Example

The **= operator.

The Exponentiation Assignment Operator raises a variable to the power of the operand.

Exponentiation Assignment Example

The /= operator.

The Division Assignment Operator divides a variable.

Division Assignment Example

The %= operator.

The Remainder Assignment Operator assigns a remainder to a variable.

Remainder Assignment Example

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The <<= Operator

The Left Shift Assignment Operator left shifts a variable.

Left Shift Assignment Example

The >>= operator.

The Right Shift Assignment Operator right shifts a variable (signed).

Right Shift Assignment Example

The >>>= operator.

The Unsigned Right Shift Assignment Operator right shifts a variable (unsigned).

Unsigned Right Shift Assignment Example

The &= operator.

The Bitwise AND Assignment Operator does a bitwise AND operation on two operands and assigns the result to the the variable.

Bitwise AND Assignment Example

The |= operator.

The Bitwise OR Assignment Operator does a bitwise OR operation on two operands and assigns the result to the variable.

Bitwise OR Assignment Example

The ^= operator.

The Bitwise XOR Assignment Operator does a bitwise XOR operation on two operands and assigns the result to the variable.

Bitwise XOR Assignment Example

The &&= operator.

The Logical AND assignment operator is used between two values.

If the first value is true, the second value is assigned.

Logical AND Assignment Example

The &&= operator is an ES2020 feature .

The ||= Operator

The Logical OR assignment operator is used between two values.

If the first value is false, the second value is assigned.

Logical OR Assignment Example

The ||= operator is an ES2020 feature .

The ??= Operator

The Nullish coalescing assignment operator is used between two values.

If the first value is undefined or null, the second value is assigned.

Nullish Coalescing Assignment Example

The ??= operator is an ES2020 feature .

Test Yourself With Exercises

Use the correct assignment operator that will result in x being 15 (same as x = x + y ).

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Updated on November 6th, 2023

Magic Squares in JavaScript

In ma thematics, a “ magic square ” is a matrix of numbers where each row, column, and diagonal add-up to the same number. That number is called the “ magic constant “. The integers used are only positive, and do not repeat . The constant sum is determined by the size of the square and is described by a formula:

Facts about the properties and classifications of these numeric formations have been discussed by scholars for millennia. Knowledge of this topic goes back thousands of years, and can be found referenced throughout the world.

History & Culture

Magic squares have a fascinating historical and cultural significance, often with mystical undertones. They are mentioned in the I Ching , Brhat Samhita , and other works concerned with the transcendental and occult. They can be seen used in art, divination, perfumery, recreational gaming, computer science, and more.

In the Brhat Samhita , the magic square is used as a symbolic representation of the planets. It makes use of magic squares in the creation of talismans for astrological purposes.

For the purposes of this blog post, we’ll view them through the lens of software engineering.

3×3 Magic Squares

There’s so much to cover on this topic. I’ll narrow it down to 3×3 lattices (magic squares can actually be any size), specifically in the context of the JavaScript programming language. A quad of numbers, like the one pictured above, can be described as a two-dimensional array:

Squares of this size always have a magic constant of 15 . And, the number 5 will be in the middle. There’s additional logic that explains which numerals can appear where and why. Those ideas are explored in the comments section of a HackerRank coding challenge titled “Forming a Magic Square”.

HackerRank Coding Challenge

This coding problem found on HackerRank asks programmers to figure out what it would take to convert a 3×3 matrix of integers into a magic square. The input array is almost valid, but requires a few replacements. For each change, we must track the difference between the numbers and return the total variance – referred to as the “cost”. The correct answer will be the lowest cost required to convert the input data into a magic square.

The difficulty of this assignment is considered “medium”. The first step is realizing that there are a finite number of valid magic square configurations. As it turns out, there are exactly eight 3×3 permutations:

Starting with any one of these, we can generate the other seven programmatically. The subsequent arrangements can be derived through rotation and reflection. Using JavaScript, I rotate an initial seed square three times to have the first four series. Then, I flip each one of those to get the final records.

To solve this exercise, we’ll take the input array and compare it to each of the valid magic squares. We keep track of the cost on each iteration, and finally return the minimum.

You’ll notice that the initial minimum cost is set to a very high number . As I loop through each of the valid magic squares, I check if the cost is lower than the current minimum and then replace the value.

With each comparison, subtraction is used to determine the cost to complete the transformation. That code loops through each digit of each row on both 2D arrays. The absolute value of the difference between each coordinate is tallied and returned.

The working code all stitched together looks like this:

This solution was not intuitive to me and took some research and experimentation. It was interesting to learn about the concept of magic squares (and other shapes) along the way.

About the author

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Anthony is a seasoned software engineer with a flair for design and a knack for problem-solving. Specializing in web development, his expertise extends beyond just coding. He crafts solutions tailored to the unique needs of small to medium-sized businesses.

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Magic Numbers

Maths and operators in js.

Made by Mick Fuzz and as a contribution to be remixed for Clubs by Mozilla .

Javascript is one of the key parts of the Web (together with HTML and CSS). Here we learn how to do some maths with Javascript and how to use operators that are key to using the language.

45 minutes to an hour

Preparation

First do the activity on your own to become familiar with it.

Then do a follow up bit of research on Javascript to help if students run in to trouble. Specifically good is this page on Chris Mills' course .

Introduction

Give a short presentation about maths and Javascript.

• Javascript has many uses on the web from games, to chat pages, shopping etc.
• Most of these uses involve using numbers and maths.
• A game which uses numbers and maths is Cookie Clicker . Have you tried it?

Javascript uses variables to rememeber and work with data. In the last session we were using variables to store the names of things. In this game Javascript variables are used to keep track of how many cookies we have created.

Each time we click the cookie the number value of the variable goes up by one, simples!

Activity One - Use the console to play with number variables

Split learners into groups of 2 or individuals if there enough computers explain that we will use the console to find out more about how numbers and maths are done in Javascript.

Ask individuals / groups to follow these instructions:

• Open Firefox (or other browser)
• Press F12 to bring up some tools
• Click on Console
• Press F12, find the Console and enter the following commands
• "hello " + "derek"

The simple way to do adding, subtracting, multipliction and division is to user the following Javascript maths Operators ?

• + Add Operator
• - Subtract Operator
• * Multiply Operator
• / Divide Operator

Discussion: Why does 2 + 3 give a different result to "2" + "3"

Wait what is happening? What are the answers to 6 and 8 different from what we got for 1?

The answers to 1,6,8 are different because we are adding different types of data.

• 2 is a datatype of number: Numbers are used for maths and calculations
• “2” is a datatype of String: Strings are used for text based data, names and addresses are common examples.

The easy way to tell the difference between a value of type number and String is by noticing if the quotation marks ("") are used.

Using the + operator has a different effect with strings and number variables. It adds together numbers with addition but strings get put next to each other like being stuck together end to end with glue. In coding this is called "concatenation".

Be careful!: If we use + with a string and a number, then both the string and number are treated as strings so the the result is a string.

Activity - Hacking Cookie Clicker

In your browser go to cookie clicker game website Press F12 - go to the console and Enter

• Game.cookies = 23570

What happens? The equal sign assigns the number value on the right to the variable on the left (Game.cookies). Because this variable is what is used by the cookie clicker game to keep a track of your score, the number used on the game goes up on your page. Amazeballs! You've hacked it!

There are other operators we can use too. What about if we wanted to add on 10 cookies to our total?

How about we want to take 100 cookies off of our total? Find out how to do this by entering the following instructions in the console window when you are playing cookie clicker.

• Game.cookies += 10
• Game.cookies -= 100
• Game.cookies *= 4

We can see that if we put a plus sign infront of our equals sign that it add on the number on the right to the current value of the variable on the left. We call this an addition assignment operator. The same idea works for subtracting, mulitplying etc.

To test out that you understand these new operators, use the console and try some examples like the one below.

Wow Factor Activity 4 - Javascript Takeover Demo

INSTALL "HEY FRENCH TOAST" EXAMPLE BOOKMARKLET

What have we learned?

There was a lot of things to learn in this session. A lot if it is quite quick to pick up but a discussion at the end to recap what we have learned is a great idea to check we are all on the path.

• We've learned about the different Data Types of Number, String and Boolean in Javascript and what we use them for.
• We've learned about how use Arithmetic Operators and Assignment Operators
• We've done an experiment to let Javascript take over our browser and pepper it with French Toast!
• And hopefully we've learned how to make a pointless game like Cookie Clicker even more pointless by cheating!

Brian P. Hogan

Technical content expert, developer, teacher, and musician

Creating a Magic 8 Ball Game with HTML, Canvas, and JavaScript

Published April 13, 2020

Reading time: 7 minutes.

The “Magic 8 Ball” is a toy shaped like the “8” ball in billiards, created in 1950. You ask a “yes” or “no” question, shake the ball, and look at the answer it provides, which you see through a window on one side of the ball.

In my book Exercises for Programmers , one of the exercises is to use arrays and random numbers to create your own Magic 8 Ball game:

Create a Magic 8 Ball game that prompts for a question and then displays either “Yes,” “No,” “Maybe,” or “Ask again later.”

One of the additional challenges in the exercise is to implement this as a GUI application. In this tutorial, you’ll do just that by using HTML, JavaScript, and the Canvas API . When you’re done, you’ll have a Magic 8 Ball game that shows you answers when you click the ball. The end result will look like this:

The Canvas API lets you create 2D raster (pixel) graphics using JavaScript. You define a canvas element on the page, grab a reference to the element in JavaScript, and then use various API methods to draw lines, rectangles, and arcs to create shapes.

You’ll draw the ball using the Canvas API, and then use an event handler to display random text when you click the ball. You can’t modify the canvas directly once you’ve drawn something, so each time you click, you’ll redraw the entire ball with new text.

Let’s get started.

Drawing the Ball

The ball will consist of three elements: a black circle for the ball itself, a blue triangle to represent the area where the text appears, and the text itself. You’ll draw the ball and the triangle first, and the

First create a new file called 8ball.html and add the following code to define a basic HTML5 skeleton with a <canvas> element in the <body> tag:

The canvas element has a height and width defined, and an ID attribute so you can grab it with JavaScript, where you’ll do all your drawing.

Next, add a <script> tag below the <canvas> element that grabs a reference to the canvas using getElementById , and a ctx variable that holds a reference to the 2D context of the canvas. This is what you’ll use to draw the ball.

Next, create a drawBall function to hold the logic to draw the ball on the canvas. The function accepts a string which contains the text that will appear on the ball. Add the following code to define the function and then invoke it so that the ball will eventually appear on the page:

Next, write the code to create the ball itself. Start by adding the following code which draws a black filled circle on the canvas:

This sets the fill color to black and then creates a circle using the arc function. The arc function takes the x and y coordinates for the center of the circle, followed by the radius, the starting angle, and the ending angle in radians. So in this case, you’re creating the circle at 150 over, 150 down, with a radius of 150, a starting angle of 0 (the top), and an ending angle of PI * 2. JavaScript has Math.PI available out of the box.

The fill function then fills in the circle with the color set with fillStyle . The words argument has a default value of an empty string so you can call drawBall with no arguments so the ball won’t display any words. This is how you’ll initialize the game.

Save the file and reload the file in your browser. You’ll see a black ball:

Now define the blue triangle which will contain the words. Set the color to blue , move the starting point to 150 pixels over and 50 pixels down. Then draw lines from the starting point to 50 across and 200 down, and then to 250 across and 200 down. Draw the third side by making the line end at the original point of 150 across and 50 down. Then fill the space:

The triangle appears inside the ball once you save the file and reload the page:

Now let’s write the game logic.

Choosing the Random Phrase

The Magic 8 Ball game logic boils down to having a list of possible phrases and choosing one at random, which you can accomplish with a very small amount of JavaScript code.

Below the const canvas line in your script block, add a constant called choices that holds the possible choices that will appear in your 8 ball. You can add more choices if you’d like.

Then create a getRandomAnswer function that selects a random value from the array using Math.Random :

This generates a random number and uses it as the array index. The Math.Random() function returns a random number between 0 and 1. The index you use to select an entry in the array needs to be between 0 and the last index of the array, so you can take the length of the choices array, multiply it by Math.random() , and then round the answer down with Math.floor() .

Now when you call getRandomAnswer() , you’ll get a random value from the choices array. Let’s hook this up to the interface.

Displaying the Result

When you click on the ball, you want the text to show up inside the triangle. To do this, you’ll need to add code to the drawBall function to display the text, and create an event listener that fetches the random answer and draws the ball.

First, add the code to display the text in the triangle. Inside the drawBall function, add the following code to display the text if the words argument contains any text:

This creates a centered text area placed at 150 across and 150 down, which is in the middle of your ball.

Now tie it all together by adding the event listener.

After the call to drawBall() , add this code which listens for click events and redraws the ball, passing in the value from the getRandomAnswer() function:

Your complete project should look like the following code:

When you save and reload the page and click the ball, you’ll see one of the phrases:

In this tutorial you created a basic implementation of a Magic 8 Ball game using the Canvas API. From here you can try the following additional exercises:

• Instead of a solid black color, use a radial gradient for the ball. Check out the CanvasGradient documentation for more.
• You can animate the canvas. Rework the code that displays the text so that it fades in and fades out. Remember that to animate the canvas, you need to redraw the canvas, so you’ll need to do some kind of animation loop.
• Try implementing this same application as a command-line tool in your favorite language, or as a mobile app.

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Answer to Question #310338 in HTML/JavaScript Web Application for vicky

Person Details

given an object person containing a person details, write a JS program to log the name, address and nicknames count.

• the input will be a single containig an object person
• the first line of output should contain the name and address of the person as shown in the sample output
• the second line of output should contain nicknames count as shown in sample output.

{ 'name':'Pranay', 'address':{'city':'Mumbai','state':'maharastra'}, 'nicknames':['nani','chanti']}

pranay is from mumbai,maharastra

pranay has 2 nicknames

"use strict";

process.stdin.resume();

process.stdin.setEncoding("utf-8");

let inputString = "";

function main() {

 let person = JSON.parse(readLine().replace(/'/g, '"'));

 /* Please do not modify anything above this line */

 /* Write your code here and log the output */

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