Chapter 2: Excercises

This page contains a set of excercises for the corresponding chapter.
Read the task description, copy the code template if present and solve it in your Eclipse.
If you are stuck, you can show the solution for this task. Be careful not to spoil the solution for yourself unnecessarily.

Contents

1. Absolute Value
2. Factorial
3. Greatest Common Divisor
4. Number Guessing Game
5. Regular Polygon
6. Turtle Stair
7. Caesar Encryption
8. Colored Polygons
9. Honeycomb

Absolute Value

Your first task is to compute the absolute value of a difference of two values using an if statement.
Print the result on the console.
You can subtract the smaller value from the bigger.
Alternatively, you can compute a - b and negate the result if it is less than 0.

program absoluteValue import IO main variable a : integer variable b : integer variable result : integer a := 42 b := 55 // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program absoluteValue import IO main variable a : integer variable b : integer variable result : integer a := 42 b := 55 // Solution 1: subtract the lesser number from the grater one if (a > b) then result := a - b else result := b - a endif IO.writeInteger(result) IO.writeLine() // Solution 2: compute a - b and negate the result if it is less than 0 result := a - b if (result < 0) then result := -result endif IO.writeInteger(result) IO.writeLine() endmain

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Factorial

Your task is to compute the factorial of an integer using a loop.
5! = 5 * 4 * 3 * 2 * 1 = 120
Print the result on the console.

program factorial import IO main variable n : integer variable result : integer n := 5 // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program factorial import IO main variable n : integer variable result : integer n := 5 result := 1 loop result := result * n n := n - 1 if n = 1 then exit endif endloop IO.writeInteger(result) endmain

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Greatest Common Divisor

Your task is to compute the greates common divisor of two values.
To do this, you can subtract the lesser value from the greater one until both values are equal.
You need to overwrite old values with new ones, e.g. is a is lesser than b, you compute the new b as b - a.
GCD of 21 and 14 is 7

program gcd import IO main variable a : integer variable b : integer IO.writeString("Enter the value of a: ") a := IO.readInteger() IO.writeString("Enter the value of b: ") b := IO.readInteger() // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program gcd import IO main variable a : integer variable b : integer IO.writeString("Enter the value of a: ") a := IO.readInteger() IO.writeString("Enter the value of b: ") b := IO.readInteger() loop if a = b then IO.writeString("The GCD is: ") IO.writeInteger(b) exit endif if a < b then b := b - a else a := a - b endif endloop endmain

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Number Guessing Game

Your next task is to implement a simple number guessing game.
The program must generate a random integer between 0 and 99, this can be done using the library operation Mathematics.randomInteger(0, 99).
To use this operation, you have to import the Mathematics library first.

The user has to enter a number.
If the number equals the random number, the program is terminated and the user is given the number of attempts required to guess the number.
If the guessed number is not equal, the program has to tell the user if it is greater or less than the random number.

The entire interaction can look like this:

Please enter a number between 0 and 99: 50 Your number is lesser than the random number. Please enter a number between 0 and 99: 70 Your number is greater than the random number. Please enter a number between 0 and 99: 60 Your number is greater than the random number. Please enter a number between 0 and 99: 55 Your number is greater than the random number. Please enter a number between 0 and 99: 52 Correct! Your number of attempts is 5

program numberGuessingGame import IO import Mathematics import Strings main variable attempts : integer variable ownNumber : integer variable randomNumber : integer attempts := 0 randomNumber := Mathematics.randomInteger(0, 99) // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program numberGuessingGame import IO import Mathematics import Strings main variable attempts : integer variable ownNumber : integer variable randomNumber : integer attempts := 0 randomNumber := Mathematics.randomInteger(0, 99) loop attempts := attempts + 1 IO.writeString("Please enter a number between 0 and 99: ") ownNumber := IO.readInteger() if ownNumber = randomNumber then IO.writeString("Correct! Your number of attempts is " & Strings.integerToString(attempts) & "\n") exit else if ownNumber > randomNumber then IO.writeString("Your number is greater than the random number.\n") else IO.writeString("Your number is lesser than the random number.\n") endif endif endloop endmain

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Regular Polygon

Your task is to draw a regular polygon using Turtle.
As a reminder, in the first chapter we have drawn a Turtle square using the following code.

program turtleExample import Turtle main variable l : integer l := 100 variable a : integer a := 90 Turtle.forward(l) Turtle.left(a) Turtle.forward(l) Turtle.left(a) Turtle.forward(l) Turtle.left(a) Turtle.forward(l) Turtle.left(a) endmain

As you can see, we repeating lines of code, which we can remove by using a loop.
At first, optimize this example using a loop to draw a square.

Once done, allow the user to enter the number of edges as well as their length to draw a generic regular polygon.
You will have to dynamically compute the angle using the number of entered edges.
For example, if the user enters 5 as the number of edges, the angle should be 72 degree, or 60 degree if the number of edges is 6.

A polygon with the following parameters should look like in the image below. Enter the number of edges: 6 Enter the length of edges: 50


program regularPolygon import IO import Turtle main // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program regularPolygon import IO import Turtle main variable edges : integer variable length : integer variable angle : rational IO.writeString("Enter the number of edges: ") edges := IO.readInteger() IO.writeString("Enter the length of edges: ") length := IO.readInteger() angle := 360.0 / edges Turtle.setDirection(90) variable i : integer loop if i = edges then exit endif i := i + 1 Turtle.forward(length) Turtle.left(angle) endloop endmain

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Turtle Stair

Your task is to implement a stair pattern using Turtle and a loop.
Start by drawing a single step of the stair.
Once done, wrap it in into a loop to get the same result as in the image.


program turtleStair import IO import Turtle main variable length : integer length := 50 Turtle.setPosition(150, 300) // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program turtleStair import IO import Turtle main variable length : integer length := 50 Turtle.setPosition(150, 300) variable i : integer loop if i > 4 then exit endif i := i + 1 Turtle.forward(length) Turtle.right(90) Turtle.forward(length) Turtle.left(90) endloop endmain

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Caesar Encryption

Implement Caesar Encryption: https://en.wikipedia.org/wiki/Caesar_cipher.


The output of the program should be: fdhvdu - caesar

program caesarEncryption import Strings import IO operation encrypt(parameter abc : string, parameter str : string) : string // IMPLEMENT ME endoperation operation decrypt(parameter abc : string, parameter str : string) : string // IMPLEMENT ME endoperation main variable abc : string variable str : string variable encryptedStr : string variable decryptedStr : string abc := "abcdefghijklmnopqrstuvwxyz" str := "caesar" encryptedStr := encrypt(abc, str) decryptedStr := decrypt(abc, encryptedStr) IO.writeString(encryptedStr & " - " & decryptedStr) endmain

Show solution

program caesarEncryption import Strings import IO operation encrypt(parameter abc : string, parameter str : string) : string variable encryptedString : string variable i : integer loop if i >= Strings.lengthOf(str) then exit endif variable index : integer variable encryptedIndex : integer variable subStr : string subStr := Strings.subString(str, i, i) index := Strings.indexOfSubString(abc, subStr) encryptedIndex := (index + 3) mod Strings.lengthOf(abc) variable encryptedSubString : string encryptedSubString := Strings.subString(abc, encryptedIndex, encryptedIndex) encryptedString := encryptedString & encryptedSubString i := i + 1 endloop return encryptedString endoperation operation decrypt(parameter abc : string, parameter str : string) : string variable decryptedString : string variable i : integer loop if i >= Strings.lengthOf(str) then exit endif variable index : integer variable decryptedIndex : integer variable subStr : string subStr := Strings.subString(str, i, i) index := Strings.indexOfSubString(abc, subStr) decryptedIndex := (index - 3) mod Strings.lengthOf(abc) variable decryptedSubString : string decryptedSubString := Strings.subString(abc, decryptedIndex, decryptedIndex) decryptedString := decryptedString & decryptedSubString i := i + 1 endloop return decryptedString endoperation main variable abc : string variable str : string variable encryptedStr : string variable decryptedStr : string abc := "abcdefghijklmnopqrstuvwxyz" str := "caesar" encryptedStr := encrypt(abc, str) decryptedStr := decrypt(abc, encryptedStr) IO.writeString(encryptedStr & " - " & decryptedStr) endmain

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Colored Polygons

Draw the image below, the colors of the polygon are randomized RGB values.

Use Turtle.setColorRGB(Mathematics.randomInteger(0, 255), Mathematics.randomInteger(0, 255), Mathematics.randomInteger(0, 255)) to set random colors.


program coloredPolygons import IO import Turtle import Mathematics main Turtle.setAnimationSpeed(Turtle.Speed.INSTANT) Turtle.setDirection(90) Turtle.setThickness(3) Turtle.setFrameSize(500, 400) Turtle.setPosition(200, 350) // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program coloredPolygons import IO import Turtle import Mathematics main Turtle.setAnimationSpeed(Turtle.Speed.INSTANT) Turtle.setDirection(90) Turtle.setThickness(3) Turtle.setFrameSize(500, 400) Turtle.setPosition(200, 350) variable edges : integer edges := 3 loop if edges > 10 then exit endif Turtle.setColorRGB(Mathematics.randomInteger(0, 255), Mathematics.randomInteger(0, 255), Mathematics.randomInteger(0, 255)) variable edge : integer edge := 1 loop if edge > edges then exit endif Turtle.forward(100) Turtle.left(360 / edges) edge := edge + 1 endloop edges := edges + 1 endloop endmain

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Honeycomb

Draw the image below.

Use Turtle.startFilledPolygon(Turtle.Colors.YELLOW)) and Turtle.endFilledPolygon() to draw filled polygons.


program honeycomb import Turtle import Mathematics main Turtle.setFrameSize(800,800) Turtle.setDirection(90) Turtle.setPosition(300, 300) Turtle.setAnimationSpeed(Turtle.Speed.INSTANT) Turtle.setThickness(3) // IMPLEMENT YOUR SOLUTION HERE // END OF IMPLEMENTATION endmain

Show solution

program honeycomb import Turtle import Mathematics main Turtle.setFrameSize(800,800) Turtle.setDirection(90) Turtle.setPosition(300, 300) Turtle.setAnimationSpeed(Turtle.Speed.INSTANT) Turtle.setThickness(3) variable length : integer length := 50 variable i : integer loop if i > 11 then exit endif variable j : integer loop if j > 3 then exit endif variable x : integer x := j * 3 * length + Mathematics.floor((i mod 2) * length * 1.5) variable y : integer y := i * Mathematics.floor((length exp 2 - (length/2) exp 2) exp (0.5)) Turtle.setPosition(100+x, 100+y) Turtle.startFilledPolygon(Turtle.Colors.YELLOW) variable edge : integer loop if edge > 5 then exit endif Turtle.forward(length) Turtle.left(360/6) edge := edge + 1 endloop Turtle.endFilledPolygon() j := j + 1 endloop i := i + 1 endloop endmain

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