MRX20 – Mission to Mars - 101 Computing

MRX20 – Mission to Mars

Posted on December 28, 2019 by Administrator Posted in Computer Science, Computing Concepts, Cryptography, Solved Challenges

The MRX20 probe was sent to Mars by the Inter-Continental Space Agency (ICSA) a few years ago. It was due to return to planet Earth just a few days ago. The probe collected a large amount of samples from the Martian soil and took thousands of high definition pictures of Mars. Initial analysis performed on site by the probe’s Artificial Intelligence seems to indicate that the probe may contain strong evidence that there is life on Mars.

Unfortunately just a few thousand miles away from Earth, the probe collided with an unidentified geostationary satellite. It was pulverised into small pieces. Most of these were either lost in space or burnt down when entering the Earth’s atmosphere. A few pieces did pierce through the atmosphere and crashed on Earth in various locations all around the globe.

The ICSA sent a team of Probe Debris Collectors (PDCs) to locate the various parts and submit back to the ICSA the exact locations and pictures of the debris found. Each PDC has been instructed to communicate with the ICSA using a secure connection using a range of encoding/encryption techniques.

The What3Words (W3W) geo-localisation system is used to inform of the exact location of the debris. Your mission is to decode the secured transmission messages to locate the position of the debris and to retrieve all the information that has been retrieved from the debris. Use this information to find out what you can learn about the existence of life on planet Mars.

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: cryptography, encryption

Caesar Shift Decoder

Posted on December 26, 2019 by Administrator Posted in Computer Science, Cryptography, Python - Intermediate, Python Challenges

A Caesar Shift cipher is a type of mono-alphabetic substitution cipher where each letter of the plain text is shifted a fixed number of places down the alphabet. For example, with a shift of 1, letter A would be replaced by letter B, letter B would be replaced by letter C, and so on. This type of substitution Cipher is named after Julius Caesar, who used it to communicate with his generals.

Key	+5
Plain text alphabet:	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z

Cipher text alphabet:	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z	A	B	C	D	E

This type of cipher is a form of symmetric encryption as the same key can be used to both encrypt and decrypt a message. (e.g. If a message is encrypted with a key of +5, it can be decrypted with a key of -5).

A cipher wheel is a tool used to help decipher a message encrypted using the Caesar cipher:

Caesar Shift Decoder

The Caesar Shift cipher is not a very secure cipher as it only has 26 different keys. It is hence possible to apply each of the 26 keys to a cipher text to retrieve the plaintext.

The aim of this challenge is to write a Python program to decode a cipher text using all 26 keys. The user will then be able to read the 26 outputs and find the output that correspond to the plaintext.

Here is the cipher text that we will try to decode:

FTMF’E AZQ EYMXX EFQB RAD YMZ, AZQ SUMZF XQMB RAD YMZWUZP. ZQUX MDYEFDAZS

From Flowchart to Python Code

Here is the flowchart for our Caesar Shift Decoder:

To fully understand this algorithm, you will need to understand how ASCII code works. The algorithm above is using the ASCII codes for the uppercase alphabet from letter A (ASCII 65) to letter Z (ASCII 90).

Your task is to write the Python code corresponding to the above flowchart in the trinket box below.
You will then be able to use your Caesar Shift Decoder to decode the following messages:

OVBZAVU, AYHUXBPSPAF IHZL OLYL. AOL LHNSL OHZ SHUKLK. ULPS HYTZAYVUN

Message #1

FTMF'E AZQ EYMXX EFQB RAD YMZ. AZQ SUMZF XQMB RAD YMZWUZP – ZQUX MDYEFDAZS

Message #2

VYUONCZOF, VYUONCZOF. GUAHCZCWYHN XYMIFUNCIH. VOTT UFXLCH

Message #3

Python Code

Tagged with: cryptography, encryption

The Dobble Algorithm

Posted on December 22, 2019 by Administrator Posted in Computer Science, Python - Advanced, Python Challenges

Dobble (Spot It! in the US) is a speedy observation card game for 2 players or more. During the game, players have to spot the identical symbol between two cards as quickly as possible to collect cards and score points.

The Dobble rule!

Each card of the deck contains 8 graphical symbols. The deck contains 55 cards in total and there is always one and only one symbol in common between any two cards of the deck.

In order to create a deck of cards to follow this rule we need to apply some mathematical logic.
The mathematics behind the game of Dobble is fully explained on this blog post: http://www.petercollingridge.co.uk/blog/mathematics-toys-and-games/dobble/.

We will base our algorithm based on the following key findings:
If a game of Dobble needs (n+1) symbols on each card, n being a primary number then we will need:

A collection of n² + n + 1 symbols
We will be able to generate n² + n + 1 unique cards

The Dobble Matrix

To complete this challenge, it may be easier to consider the following Matrix used for a game of Dobble with only 4 symbols per card (n=3).
We will use 3² + 3 + 1 = 13 symbols to generate 13 cards with 4 symbols per card.

This matrix enables us to visualise which symbols will appear on each card and it also enables us to check that any two cards of the deck have one and only one symbol in common.

The real game of Dobble has 55 cards with eight symbols on each card. Note that with 8 symbols per card, it would have been possible to create 57 cards following the Dobble rules (7² + 7 + 1 = 57) . For some reason, 2 cards were dismissed and the actual game only contains 55 cards.

The Dobble Algorithm

For this challenge we have decided to write an algorithm to generate the 57 possible cards for a game for Dobble. The algorithm will be based on the symbols used in the real game. The challenge consists of identifying the 8 symbols to be be used on each of the cards, making sure that the Dobble rule is always respected:

There must always be one and only one symbol in common between any two cards of the deck.

Python Code/Solution

Manhattan distance calculator

Posted on December 19, 2019 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges

When calculating the distance between two points on a 2D plan/map we often calculate or measure the distance using straight line between these two points. Thought this “as the crow flies” distance can be very accurate it is not always relevant as there is not always a straight path between two points.

The perfect example to demonstrate this is to consider the street map of Manhattan which uses a grid-based layout: a mesh of horizontal and vertical roads crossing at a right angle.

Distance “as the crow flies”

The shortest distance between two points on a 2D grid is the distance using a straight line path between these two points.

On a 2D plan, using Pythagoras theorem we can calculate the distance between two points A and B as follows:

Manhattan Distance (aka taxicab Distance)

The Manhattan distance (aka taxicab distance) is a measure of the distance between two points on a 2D plan when the path between these two points has to follow the grid layout. It is based on the idea that a taxi will have to stay on the road and will not be able to drive through buildings! The following paths all have the same taxicab distance:

The taxicab distance between two points is measured along the axes at right angles.

Note that the taxicab distance will always be greater or equal to the straight line distance.

Python Implementation

Check the following code to see how the calculation for the straight line distance and the taxicab distance can be implemented in Python.

Tagged with: Coordinates

Secret Santa’s Ciphers

Posted on December 17, 2019 by Administrator Posted in Computer Science, Computing Concepts, Cryptography, Solved Challenges

It’s only few days before Christmas so here are some secret messages from Santa for you to decode…

Secret Message #1, encoded using Maritime Signal Flags

International maritime signal flags are various flags used to communicate with ships. Each flag represents a letter of the alphabet or a digit (0 to 9). You may need to research on the internet to find out the whole list of flags.

Secret Message #2, encoded using a Pigpen cipher

A pigpen cipher is a type of visual cryptography where each character of the alphabet is replaced with a symbol.

Secret Message #3, encoded using Morse code

Morse code is a method of transmitting text information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment. Each character (letter or numeral) is represented by a unique sequence of dots and dashes. The duration of a dash is three times the duration of a dot.

Secret Message #4, encoded using Semaphore Flags

Flag semaphore is a telegraphy system conveying information at a distance by means of visual signals with hand-held flags. Information is encoded by the position of the flags. The current flag semaphore system uses two short poles with square flags, which a signalman holds in different positions to signal letters of the alphabet and numbers. The signalman holds one pole in each hand, and extends each arm in one of eight possible directions. At sea, the flags are coloured red and yellow, while on land, they are white and blue.

Secret Message #5, encoded using a rail-fence cipher

The rail fence cipher (sometimes called zigzag cipher) is a transposition cipher that jumbles up the order of the letters of a message using a basic algorithm.
The rail fence cipher works by writing your message on alternate lines across the page, and then reading off each line in turn. You can read more about the rail-fence cipher on this page.

Secret Message #6, encoded using a mono-alphabetic substitution cipher

A mono-alphabetic cipher (aka simple substitution cipher) is a substitution cipher where each letter of the plain text is replaced with another letter of the alphabet. It uses a fixed key which consist of the 26 letters of a “shuffled alphabet”.

You can decipher a mono-alphabetic cipher using a frequency analysis.

Cipher Text:

“G RGXX XGMK GO BAK YULB, BAK YHKLKOB, UOQ BAK PCBCHK!”, LNHIIZK HKYKUBKQ, UL AK LNHUVJXKQ ICB IP JKQ. “BAK LYGHGBL IP UXX BAHKK LAUXX LBHGMK RGBAGO VK. IA WUNIJ VUHXKS! AKUMKO, UOQ BAK NAHGLBVUL BGVK JK YHUGLKQ PIH BAGL! G LUS GB IO VS DOKKL, IXQ WUNIJ; IO VS DOKKL!”

AK RUL LI PXCBBKHKQ UOQ LI ZXIRGOZ RGBA AGL ZIIQ GOBKOBGIOL, BAUB AGL JHIDKO MIGNK RICXQ LNUHNKXS UOLRKH BI AGL NUXX. AK AUQ JKKO LIJJGOZ MGIXKOBXS GO AGL NIOPXGNB RGBA BAK LYGHGB, UOQ AGL PUNK RUL RKB RGBA BKUHL.

“BAKS UHK OIB BIHO QIRO”, NHGKQ LNHIIZK, PIXQGOZ IOK IP AGL JKQ–NCHBUGOL GO AGL UHVL, “BAKS UHK OIB BIHO QIRO, HGOZL UOQ UXX. BAKS UHK AKHK—G UV AKHK—BAK LAUQIRL IP BAK BAGOZL BAUB RICXQ AUMK JKKO, VUS JK QGLYKXXKQ. BAKS RGXX JK. G DOIR BAKS RGXX!”

AGL AUOQL RKHK JCLS RGBA AGL ZUHVKOBL UXX BAGL BGVK; BCHOGOZ BAKV GOLGQK ICB, YCBBGOZ BAKV IO CYLGQK QIRO, BKUHGOZ BAKV, VGLXUSGOZ BAKV, VUDGOZ BAKV YUHBGKL BI KMKHS DGOQ IP KEBHUMUZUONK.

“G QIO’B DOIR RAUB BI QI!”, NHGKQ LNHIIZK, XUCZAGOZ UOQ NHSGOZ GO BAK LUVK JHKUBA; UOQ VUDGOZ U YKHPKNB XUINIIO IP AGVLKXP RGBA AGL LBINDGOZL. “G UV UL XGZAB UL U PKUBAKH, G UV UL AUYYS UL UO UOZKX, G UV UL VKHHS UL U LNAIIXJIS. G UV UL ZGQQS UL U QHCODKO VUO. U VKHHS NAHGLBVUL BI KMKHSJIQS! U AUYYS OKR SKUH BI UXX BAK RIHXQ. AUXXI AKHK! RAIIY! AUXXI!”

AK AUQ PHGLDKQ GOBI BAK LGBBGOZ–HIIV, UOQ RUL OIR LBUOQGOZ BAKHK: YKHPKNBXS RGOQKQ.

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
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Tagged with: cryptography, encryption

Level generation using a 2D array

Posted on December 16, 2019 by Administrator Posted in Computer Science, HTML, CSS & JavaScript, JavaScript

In this post we will investigate how to generate a level/stage for a platform game using a 2D array.

We will focus on the level for a 2D platform game such as Super Mario:

By applying a grid layout to this stage, we can break down the stage in a collection of tiles. We can then store each tile using a 2D array as follows:

In this array, each tile can be associated with an integer value. For instance, in the above array/grid, a 1 represents a platform, a 2 represents a gold coin.

In javascript, the 2D array for this stage would be initialised as follows:

var grid = [
  [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0],
  [0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0],
  [0,0,0,1,1,0,0,0,0,0,0,0,1,1,0,0,0,0],
  [0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0],
  [0,0,0,0,0,0,1,1,1,1,0,0,0,0,0,0,0,0],
  [1,1,0,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0],
  [0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,0,0],
  [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]
];

Using nested loops, we can then write an algorithm to scan through all the values of the array and display each tile corresponding to their integer value accordingly.

See the Pen
Level Generator by 101 Computing (@101Computing)
on CodePen.

Please note that using a 2D array approach to store the details of a stage/level is not the only approach available. Other approaches could be used such as storing the position and dimensions of each platform in a list. The use of a 2D array in a more advanced game could quickly become too “greedy” in terms of memory use.

Adapt the code…

Using a 2D array approach can be used to create games using a top-down view such as Pacman. You can adapt the above code to recreate a maze used in a Pacman game as follows:

Tagged with: 2D Array

Heads or Tails

Posted on November 26, 2019 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

In this challenge we will create a game of heads to tails using the following rules:

The game will consist of 5 rounds.
In each round:
- the user will make a guess,
- the computer will flip a coin,
- the player will score 1 point for a correct guess.

In order to complete this game we will first create a function called flipCoin() to flip a coin and return the value “Heads” or “Tails”.

Here is the flowchart for this function:

We will then use this function in our game:

From flowchart to Python code

Using both flowcharts provided above, you can now implement the full code for this game:

Extension Task #1

Can you tweak this code so that the user can only enter the value “Heads” or “Tails” and nothing else. (If they do, the program should ask them to re-enter their guess until they enter a valid guess.)

Extension Task #2

Add some code so that when the 5 rounds are over, the user is given the option to either start a new game or to quit.

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Flowchart

Javascript: Alert, prompt or confirm?

Posted on November 23, 2019 by Administrator Posted in Computer Science, HTML, CSS & JavaScript, JavaScript

Javascript popup box are extremely useful when you start coding in Javascript. They enable you to write basic programs based on the Input/Process/Output very easily.

alert(“…”)

An alert box is an easy approach in javascript to display a message to the end user. It can be used as a form of output (equivalent to a print() statement in Python). The main drawback (or benefit?) of an alert box is that the Javascript code will pause until the user closes the popup box.

alert("Hello world!");

Try this code!

prompt(“…”)

An prompt box is an easy approach in javascript to retrieve a user input from the end user. It can be used as a form of input (equivalent to a input() statement in Python). The value returned by a prompt() function can then be stored in a variable.

var name;
name = prompt("What's your name?");
alert("Hello " + name + "!");

Try this code!

confirm(“…”)

A confirm box is used when you need the user to verify or accept something.
When a confirm box pops up, the user has to click either “OK” or “Cancel” to proceed.
If the user clicks “OK”, the box returns true. If the user clicks “Cancel”, the box returns false.

var play = confirm("Would you like the play a game of heads or tails?");
if (play==true) {
   if (Math.floor(Math.random() * 2) == 0) {
      alert("Heads!");
   } else {
      alert("Tails!");
   }
} else {
   alert("Good bye then!");
}

Try this code!

Your Turn

Use the codepen below to create pure Javascript games or programs based on the input/process/output model.
You can look at the following challenges to implement these using Javascript.

See the Pen
Heads or Tails by 101 Computing (@101Computing)
on CodePen.

Network Design Tasks

Posted on November 23, 2019 by Administrator Posted in A Level Concepts, Computer Networks, Computer Science, Computing Concepts, GCSE Concepts, Solved Challenges

In this post we will investigate the different components needed to set up a network. We will investigate specific customer requirements to create suitable network designs.

You will use our online network design tool to create these designs using the relevant hardware and cables.

Before attempting this task, you may want to read more about the different network components and their purpose.

Customer ACustomer BCustomer C

Customer A

Customer A is a recruitment agency that employs 7 members of staff working in a small office.

They would like to have enough desktops for each employee to be able to work at the same time.
They would like all files to be stored on a central server.
Each employee is provided with a laptop or smartphone which they will need to connect to the network using a wireless connection.
They should be able to access the internet.
They want to have a secure connection that prevents unauthorised requests entering the network.

Design Your Own Network Online

Video Tutorial

Customer B

Customer B is web design agency that employs 5 members of staff working in a small office.

They would like to have enough desktops for each employee to be able to work at the same time.
They would like to connect a printer to the network.
They would like all files to be stored on a central server.
They should be able to access the internet.
They would like to set up email accounts using their own email server.
They design webpages for their customers and would like to host them on their own servers.
They would like a centralised solution to back up all their files.
They need a secure connection that prevents unauthorised access to the network.

Design Your Own Network Online

Customer C

Customer C is a primary school that has 3 IT classrooms with 8 desktop computers per room.

They would like all desktops to be connected in a local area network.
They would also like the 5 teachers to have wireless access to the LAN using their own laptops.
They would like all students’ files to be stored on a central server.
They would like a centralised backup solution to backup all students files every night.
All desktops and laptops should be able to access the internet.
They would like to have a printer in each IT room and a centralised approach to organise printer credits and print queues.
They would like to set up email accounts using their own email server.
They would like to apply specific education filters to restrict students access to specific webpages.
They would like to improve the performance of the network by temporary caching webpages that have been accessed by students.
They need a secure connection that prevents unauthorised access to the network.

Design Your Own Network Online

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Networks

Divisibility Rules

Posted on November 18, 2019 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges

For this challenge we will investigate a range of algorithms used to apply some of the most common divisibility rules. We will first focus on the divisibility rule of 3 to introduce the concept of recursion.

A divisibility rule is a shorthand way of determining whether a given integer is divisible by a fixed divisor without performing the division, usually by examining its digits

Divisibility rule

So, for this challenge we will focus on implementing the divisibility rules using some python scripts without using the DIV (//) or MOD (%) operators. In reality, these operators would be a more elegant way of checking if a number is divisible by another number.

Divisibility Rule for 2

A number is divisible by 2 if its last digit is a multiple of 2. (e.g. 0,2,4,6,8)

Divisibility rule for 2

Let’s look at the following example: is 378 divisible by 2? Yes because its last digit, 8 is a multiple of 2.

Let’s write a Python a function to implement this divisibility rule for 2:

Divisibility Rule for 3

A number is divisible by 3 if the sum of all its digits is divisible by 3.

Divisibility rule for 3

Let’s look at the following example: is 378 divisible by 3?

Our aim is to write a function that takes a number as a parameter and returns whether this number is divisible by 3. To implement this function we will use a recursive function (A function with a call to itself).

Your Task

Your task is to adapt the above algorithms to implement the divisibility rules for 4,5,6.

A number is divisible by 4, if the number formed by its last two digits is divisible by 4.

Divisibility rule for 4

A number is divisible by 5, if its last digit is either a 0 or a 5.

Divisibility rule for 5

A number is divisible by 6, if it is divisible by 3 and by 2.

Divisibility rule for 6

Extension Task: Divisibility rule for 7

Apply a recursive method to find out is a number is divisible by 7. First you will need to read more about the divisibility rule for 7 on this wikipedia page.

Tagged with: recursion

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Solution...

Caesar Shift Decoder

From Flowchart to Python Code

Python Code

The Dobble rule!

The Dobble Matrix

The Dobble Algorithm

Python Code/Solution

Distance “as the crow flies”

Manhattan Distance (aka taxicab Distance)

Python Implementation

Secret Message #1, encoded using Maritime Signal Flags

Secret Message #2, encoded using a Pigpen cipher

Secret Message #3, encoded using Morse code

Secret Message #4, encoded using Semaphore Flags

Secret Message #5, encoded using a rail-fence cipher

Secret Message #6, encoded using a mono-alphabetic substitution cipher

Solution...

Adapt the code…

From flowchart to Python code

Extension Task #1

Extension Task #2

Solution...

alert(“…”)

prompt(“…”)

confirm(“…”)

Your Turn

Customer A

Video Tutorial

Customer B

Customer C

Solution...

Divisibility Rule for 2

Divisibility Rule for 3

Your Task

Extension Task: Divisibility rule for 7

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