Break Even Point

Posted on April 2, 2017 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

In Business or Economics the Break Even Point (BEP) is the point at which the total of fixed and variable costs of a business becomes equal to its total revenue. At this point, a business neither earns any profit nor suffers any loss. The following graph explains all the concepts used to find out the break even point:

Scenario

Let’s consider an online Bakery that specialises in selling Birthday Cakes online. The owner of the bakery has estimated all the costs involved and grouped them into two categories:

Fixed Costs: These costs will remain the same and do not vary depending on the number of cakes being sold. They include:
- The rent,
- Purchasing Cooking Equipment,
- Utility Bills,
- Website (Setup and maintenance/hosting).
Variable Costs: These costs will vary depending on the number of cakes being sold. They include:
- Ingredients,
- Packaging,
- Delivery Fees.

The total costs of this online bakery consist of the fixed costs plus the variable costs and can be calculated using the following formula:

Total Costs = fixed costs + (variable costs x number of cakes sold)

The revenues of this online bakery consist of the money received when selling cakes. They can be calculated using the following formula:

Revenues = average cake price x number of cakes sold

The question we are trying to answer is as follows:

What is the break even point of this online bakery? In other words, how many cakes will need to be sold to cover all the costs and start making a profit?

We can answer this question using the following formula:

Number of Cakes to break even = Fixed Costs / (Average Price – Variable Costs)

Coding Challenge

We have listed all the costs of our online bakery, both fixed and variable into a text file.

The average price per cake is £16.00.

Use a Python program to extract the relevant information from the text file in order to:

Calculate the sum of all fixed costs.
Calculate the sum of all variable costs.
Find out the break even point for this business: how many cakes will need to be sold to cover all the costs and start making a profit?

The text file we will use contains one line per cost as follows:

Description;Type of cost (fixed cost or variable cost);Value (in pounds);

costs.txt

To complete this challenge you will need to read more about how to read through a CSV file.

Solution...

The solution for this challenge is available to full members!
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Tagged with: CSV, File Handling

Curling Challenge

Posted on April 1, 2017 by Administrator Posted in Computer Science, Python - Advanced, Python Challenges, Solved Challenges

Curling is a sport in which players slide stones on a sheet of ice towards a target area which is segmented into four concentric circles. Two teams, each with four players, take turns sliding heavy, polished granite stones, also called rocks, across the ice curling sheet towards the house, a circular target marked on the ice. Each team has eight stones. The purpose is to accumulate the highest score for a game; points are scored for the stones resting closest to the centre of the house at the conclusion of each end, which is completed when both teams have thrown all of their stones. A game usually consists of eight or ten ends.

Challenge #1

We have created a Python script using Python Turtle to represent the target as well as the eight stones, randomly positioned above the target. Our algorithm randomly generates x and y coordinates between -170 and 170 for both coordinates. Each stone is a circle with a radius of 24 pixels. However our algorithm is not realistic as sometimes the stones are overlapping which would be impossible in a real game of curling.

Your challenge consists of tweaking this code to prevent two stones from overlapping. To ensure that there is no overlap between two stones you will need to use Pythagora’s theorem:

Complete the code

Challenge #2

The team who wins is the team who has the closest stone (to the centre of the target: coordinates (0,0)).

In this case the team scores points based on the number of stones resting closer to the target than any of the stones of the opposite team.

Your challenge consists of tweaking your code to find out who is the winning team and to calculate the score of the winning team.

Solution...

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Tagged with: Coordinates, Turtle

Darts Scoring Algorithm

Posted on March 31, 2017 by Administrator Posted in Computer Science, Python - Advanced, Python Challenges, Solved Challenges

The following diagram explains how a dart is allocated a score in a game of darts.

To calculate the score of an arrow based on its (x,y) coordinates we will use two calculations:

The distance of the arrow from the centre of the target,
The angle matching the arrow position.

Calculating the distance

To calculate the distance of the arrow from the centre of the target, we will use the Pythagora’s Theorem:

You can review this blog post where we have used a similar approach to calculate the score of an arrow in a game of archery.

We will then be able to use this distance to check where the arrow landed:

Bull’s Eyes (Red inner circle)
Bull (Green inner circle)
On target (Black or white zones)
On the triple ring
On the double ring
Outside of the target

To do so you will need the dimensions of the target (in pixels). These are given on the diagram below:

Calculating the angle

To calculate the angle we will use the trigonometric formulas (SOCATOA):

Using the following angles your program can then figure out the score for the arrow:

Complete the code

Check the code below used to display the dartboard and to throw an arrow by generating random (x,y) coordinates.

Complete the code to calculate both the distance and the angle of the arrow based on the (x,y) coordinates of the arrow. Use this information to find out the actual score of the arrow.

Extension Task

Adapt your code so that the computer throws three darts. Your script should then calculate the total score of the three darts.

Solution...

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Tagged with: Coordinates, Turtle

Factorial Challenge

Posted on March 29, 2017 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

In Mathematics, the factorial of n is denoted by n! and calculated by the product of integer numbers from 1 to n.

For instance:

In this challenge you will write a Python program that asks the user to enter a positive number. In return the program will output the factorial of this number.

Iterative Approach

n! = n x (n-1) x (n-2) x (n-3) x … x 4 x 3 x 2 x 1

Your task: Write a function to calculate n! using an iterative approach.

Recursive Approach

Another approach to define the factorial of a number n is to use a recursive approach:

n! = n x (n-1)!

Your task: Write a function to calculate n! using a recursive approach.

0! = 1

The factorial calculations given above work for any positive integer greater than 0.

There is however an exception for the value 0 as 0! = 1.

Amend your code to ensure that if the user enters the value 0, both your functions return the value 1.

Also, add some input validation to ensure that the user does not enter a negative value.

Help?

Check this blog post for some help on how to complete this challenge.

Did You Know?

Six weeks is exactly 10! seconds (=3,628,800)

6 Weeks, 7 Days per week:	6 x 7 days
6 Weeks, 24 hours per day:	6 x 7 x 24 hours
6 Weeks, 60 minutes per hour:	6 x 7 x 24 x 60 minutes
6 Weeks, 60 seconds per minute:	6 x 7 x 24 x 60 x 60 seconds
Factor some numbers:	6 x 7 x (8 x 3) x (3 x 4 x 5) x (2 x 3 x 10)
Rearrange:	10 x 3 x 3 x 8 x 7 x 6 x 5 x 4 x 3 x 2
Lastly as 3 x 3 = 9	10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2

There are 52! ways to shuffle a deck of cards.

That is 8.0658175… × 10⁶⁷

Solution...

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Tagged with: iteration, recursion

Kings & Queens of England

Posted on March 19, 2017 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

Portrait of Henry VIII

There have been 66 monarchs of England and Britain spread over a period of 1500 years.

For this Python challenge you will use a text file listing all of these monarchs in chronological order. You will then write a Python program to prompt the user to enter a year (between 757 and 2017) and your program will look up for the name of the monarch of England at the given date.

To complete this challenge you will need to read more about how to read through a CSV file.

The text file we will use contains one line per monarch. On each line it stores the year the reign started, the year it ended and the name of the monarch as follows:

StartYear,EndYear,Name

Monarchs-of-England.csv

Complete the Code

Testing

Once you have completed the code check that it produces the expected output by performing the following tests:

Test #	Input Values	Expected Output	Actual Output
#1	1192	Richard I
#2	1345	Edward III
#3	1042	Harthacanut Edward the Confessor
#4	1547	Henry VIII Edward VI
#5	1016	Ethelred II the Unready Edmund lronside Cnut (Canute)
#6	512	Not Found

Extension Task:

Tweak the output of your program so that when giving the name of the monarch matching the year entered, your program also mentions who were the previous monarch and the next monarch.

For instance the output of the program could be:

In 1192, the monarch of England was Richard I. Their predecessor was Henry II up until 1189 and their successor was John whose reign started in 1199.

Video Tutorial

Solution...

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Tagged with: CSV, File Handling, Linear Search

Professor Snape’s Magic Potions

Posted on March 18, 2017 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

In this challenge we will use file handling techniques to read through and access the content of different text files.

We have saved three recipes for the following three magic potions using one text file per recipe:

Invisibility Potion:
A potion that makes you invisible for a short period of time.
Aging Potion:
A potion which causes the drinker to temporarily become older. The more of the potion is drunk, the larger the aging which occurs.
Poison Antidote:
A potion which counteracts ordinary poisons, such as creature bites and stings.

The following Python code opens the text file of the invisibility potion (invisibility-potion.txt) in read-only mode. It then uses a for loop to access and print the content of each line, one line at a time.

Your Challenge

Your challenge consists of adding a menu to this code to let the user decide which potion to display on screen. Based on their choice, the program will open the relevant text file and display the recipe on screen.

Extension Task

Add an extra text file to store this new potion:

Babbling Beverage
A potion that causes uncontrollable speaking of nonsense.

Video Tutorial

Solution...

The solution for this challenge is available to full members!
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Tagged with: File Handling, Function, Procedure, subroutine

Mind the Gap

Posted on March 11, 2017 by Administrator Posted in Computer Science, HTML, CSS & JavaScript, JavaScript

When your browser displays a webpage on screen it uses 3 different programming languages called HTML, CSS and JavaScript. We call the combination of these three languages “client-side web technologies”.

Each of the three language has its own syntax and purpose:

HTML uses <tags> and its purpose is to add content on the page such as text, pictures, and video clips.
CSS is used to customise the look and feel of the page by defining the position of each element on the page, defining the layout of the page as well as formatting text, pictures and other components on the page.
JavaScript is used to add user interaction to the page. JavaScript can be linked to HTML tags through various events such as the onClick event of a button.

Each of these languages are based on web standards defined by the World Wide Web Consortium W3C. As a consequence these languages are recognised by all the main web-browsers including Google Chrome, Microsoft Edge, Modzilla Firefox, Safari, etc. on various platforms (Windows, MacOs, Linux, Android etc.)

The Following codepen provides a clear demonstration of the syntax and purpose of HTML, CSS and JavaScript and shows how JavaScript can interact with various HTML tags.

On this codepen you can click the button located below the “Mind the Gap” sign in order to change the text of the sign.

Edit this code in a new window using this button:

Your Challenge:

Add one more button to allow the user to change the background colour of the both sections of the logo (circle and label).

To do so you will need to:

Add a button below the poster
Create a new Javascript function called changeColours() and add Javascript code to prompt the user to enter two colour codes (hexadecimal format: e.g. #00FF00). Use some of the code as provided below to change the colour of the red circle or of the blue label.
```
document.getElementById("red-circle").style.borderColor = "#FFFF00";
document.getElementById("blue-label").style.backgroundColor = "#00FF00";
```

You can then use your web application to re-create the following signs:

Tagged with: CSS, HTML, JavaScript

Keep Calm and Carry On Coding

Posted on March 9, 2017 by Administrator Posted in Computer Science, HTML, CSS & JavaScript, JavaScript

Each of the three language has its own syntax and purpose:

HTML uses <tags> and its purpose is to add content on the page such as text, pictures, and video clips.
CSS is used to customise the look and feel of the page by defining the position of each element on the page, defining the layout of the page as well as formatting text, pictures and other components on the page.
JavaScript is used to add user interaction to the page. JavaScript can be linked to HTML tags through various events such as the onClick event of a button.

The Following online web editor provides a clear demonstration of the syntax and purpose of HTML, CSS and JavaScript and shows how JavaScript can interact with various HTML tags.

On this preview you can click the button located below the poster in order to change the text of the poster.

Edit this code in a new window using this button:

Your Challenge #1:

Add four more buttons to allow the user to change the background colour of the poster:

Blue Button: Change colour to: #3050D0
Yellow Button: Change colour to: #CEC110
Orange Button: Change colour to: #ED3300
Red Button: Change colour to: #DB0000

To do so you will need to:

Add some buttons below the poster
Ensure the <DIV> tag has an id attribute. e.g. id=”poster”
Create a new Javascript function called changeColour() and use the follwoing code
```
document.getElementById("poster").style.backgroundColor = "#3050D0";
```

Your Challenge #2:

Add four more buttons to allow the icon used in the poster:

Crown Button: Change the picture to the crown:
https://www.101computing.net/wp/wp-content/uploads/Keep-calm-and-carry-on-crown.png
HTML Button: Change the picture to:
https://www.101computing.net/wp/wp-content/uploads/html-icon.png
CSS Button: Change the picture to:
https://www.101computing.net/wp/wp-content/uploads/css-icon.png
JavaScript Button: Change the picture to:
https://www.101computing.net/wp/wp-content/uploads/javascript-icon.png

To do so you will need to:

Add some buttons below the poster
Ensure the <IMG> tag has an id attribute. e.g. id=”icon”

Create a new Javascript function called changeIcon() and use the follwoing code

document.getElementById("icon").src = "https://www.101computing.net/wp/wp-content/uploads/html-icon.png";

Use your application to recreate the following three posters:

Tagged with: CSS, HTML, JavaScript

Time Guessing Game

Posted on March 7, 2017 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

Reaction Time Tester

Look at the code provided below. It uses the time library to store the current time (as a number of seconds) at different lines of the code.

The code is executed very quickly, normally in just a few milliseconds, one line at a time. This is called sequencing. However from time to time your code is paused, waiting for the user to input a value. This is the case in Python every time you use the input instruction.

By recording the current time before and after an input instruction, we can then calculate how long it took for the user to type an answer. This is the approach used by the following Python program used to calculate your reaction time (how quickly will you press the return key).

Time Guessing Game

Adapt this script to:

Generate a random number between 1 and 10,
Display the number on screen and ask the user to wait for this number of seconds before pressing the return key,
Calculate how long they waited for and give the user a score as follows:

If the user waited for more than the given time, they went bust: 0 points,
If the user press the return key at the right time or up to 1/2 second earlier: 50pts,
If the user press the return key between 1 second to 1/2 second earlier: 25pts,
If the user press the return key between 2 seconds to 1 second earlier: 10pts,
If the user press the return key more than 2 seconds earlier: 0pts.

Solution...

The solution for this challenge is available to full members!
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Tagged with: Date & Time

Fast Typing Test

Posted on March 7, 2017 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

Reaction Time Tester

Look at the code provided below. It uses the time library to store the current time (as a number of seconds) at different lines of the code.

Fast Typing Challenge

Adapt this script to measure how long it will take the end-user to type the entire alphabet (“abcdefghijklmnopqrstuvwxyz”).

Once the user has typed the alphabet, check that they typed it correctly. If not the user should try again until they type it right.

The program should then output:

How many attempts they had,
How long it took them in total,
How long it took them on average per attempt,
How long it took them on their last attempt (which is when they got it correct).

Extension Task

Add a menu system to offer three levels.

Level 1: The user has to type the alphabet,
Level 2: The user has to type the following quote: “The quick brown fox jumps over the lazy dog”.
Level 3: A random quote is picked alongside a list of the following three pangrams^(*):

“The quick brown fox jumps over the lazy dog”
“The five boxing wizards jump quickly”
“Pack my box with five dozen liquor jugs”

^(*)A pangram, or holoalphabetic sentence, includes every letter of the alphabet at least once. The most challenging pangrams are the ones with the fewest letters.

Solution...

The solution for this challenge is available to full members!
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Tagged with: Date & Time

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Scenario

Coding Challenge

Solution...

Challenge #1

Complete the code

Challenge #2

Solution...

Calculating the distance

Calculating the angle

Complete the code

Extension Task

Solution...

Iterative Approach

Recursive Approach

0! = 1

Help?

Did You Know?

Six weeks is exactly 10! seconds (=3,628,800)

There are 52! ways to shuffle a deck of cards.

Solution...

Complete the Code

Testing

Extension Task:

Video Tutorial

Solution...

Your Challenge

Extension Task

Video Tutorial

Solution...

Your Challenge:

Your Challenge #1:

Your Challenge #2:

Reaction Time Tester

Time Guessing Game

Solution...

Reaction Time Tester

Fast Typing Challenge

Extension Task

Solution...

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