Little book of programming challenges
- 2. 2 The following challenges are here to challenge and inspire you as well as help you on your journey to becoming a ‘computational thinker’. You may be set these as homework or in the classroom. Try to com- plete them to the best of your ability. If you can’t write a successful solution don't worry, you are still learning from the attempt you have made. Try to complete the extension exercises too whenever possible— extension doesn't mean ‘optional’! Writing programs can be frustrating - if you get stuck don't give up! Use the internet for help (but not the answer!) Use the help features of the programming development envi- ronment. Use features like break points and variable watches to try to work out what is happening if the program doesn’t seem to work. Work with other students on the course—’two heads are bet- ter than one’ 23 Challenge 26 CodeBreaker The computer generates a 4 digit code The user types in a 4 digit code. Their guess. The computer tells them how many digits they guessed correctly Extension : the computer tells them how many digits are guessed correctly in the correct place and how many digits have been guessed correctly but in the wrong place. The user gets 12 guesses to either win – guess the right code. Or lose – run out of guesses. Challenge 27 HangMan Player 1 types in a word Player 2 has to guess the word in 5 lives The display would look like this Word to guess: ****** You have 5 lives left - Letter? E Word to guess: **EE*E You have 5 lives left - Letter? Z Word to guess: **EE*E You have 4 lives left - Letter?
- 3. 22 Challenge 25 Remember Challenge 9? Write a program that will generate a random playing card e.g. ‘9 Hearts’, ‘Queen Spades’ when the return key is pressed. Rather than generate a random number from 1 to 52. Create two random numbers – one for the suit and one for the card. However we don't want the same card drawn twice. Update this program by using an array to prevent the same card being dealt twice from the pack of cards. Convert this code into a procedure ‘DealCard’ that will display the card dealt or ‘no more cards’. Call your procedure 53 times! Challenge 25 Extended Blackjack. Play a game that draws two random cards (see above). The player then decides to draw or stick. If the score goes over 21 the player loses (goes ‘bust’). Keep drawing until the player sticks. After the player sticks draw two computer cards. If the player beats the score they win. Added complication : Aces can be 1 or 11! The number used is whichever gets the highest score. 3 Challenge 1 Write a program that will display a joke Don’t display the punchline until the reader hits the enter key. Extension display the punchline in a different colour Prior Knowledge Needed How to output information to the screen Challenge 2 Write a program that will ask you your name It will then display ‘Hello Name’ where ‘Name’ is the name you have entered. E.g. What is your name? Ada Hello Ada Prior Knowledge Needed How to create variables How to input data into a variable How to display variables
- 4. 4 Challenge 3 Write a program to work out the areas of a rectangle. Collect the width and height of the rectangle from the keyboard Calculate the area display the result. Extension display the volume of a cu- boid. See what happens when you don't type in numbers! - Try to explain what has hap- pened and why Prior Knowledge Needed How to create variables How to input data into a variable How to display variables How to perform basic mathematical calculations Challenge 4 Write a program that will work out the distance travelled if the user enters in the speed and the time. Extension Get the program to tell you the speed you would have to travel at in order to go a distance within a certain time entered by the user. 21 Challenge 24 Create a program with the following record structure Structure Results HomeTeam as string HomeTeamScore as integer AwayTeam as string AwayTeamScore as integer End Structure Make an array of 20 Results Create a program with a menu whose options are 1. Add a result 2. Search for all results for a team Write the code to carry out these two things. If option 1 is selected collect the result and add it to the end of the results array If option 2 is selected Collect team name display all the results that in includes that team in either the home or away team Hint Include a variable to store the current number of results Prior Knowledge Needed How to create record structures Creating arrays of record struc- tures Iteration and selection
- 5. 20 Challenge 22 Create a two-dimensional array of integers 10 by 10. Fill the array with random numbers in the range 0 to 15 Display the array on the screen showing the numbers Display the array on the screen as spaces whose BackColor prop- erty has been set to the number in this position of the array. Prior Knowledge Needed How to create 2D arrays Using nested loops Challenge 23 Create a simple treasure hunt game. Create a two-dimensional array of integers 10 by 10. In a random position in the array store the number 1. repeat Get the user to enter coordinates where they think the treasure is. If there is a 1 at this position display ‘success’. Until they find the treasure Extension Add a feature to say ‘hot’ ‘cold’ ‘warm’ depending on how close their guess was to the actual hid- den location. Prior Knowledge Needed How to create 2D arrays 5 Prior Knowledge Needed How to create variables How to input data into a variable How to display variables How to use system functions. How to use system variables Challenge 5 Write a program to work out how many days you have lived for. Agorithm Enter date of birth Get today’s date Get the difference in days between the two dates Display result Extension Work out how many seconds you’ve lived for. Hints Use Date.Now to get today’s date Use the date type for a variable to store your date of birth Use the datediff function to get the difference between two days
- 6. 6 Challenge 6 Make a game for seeing how good people are at guessing when 10 seconds have elapsed. Algorithm Tell them to hit enter key when ready Get the first time in seconds Get them to hit the enter key when they think time has elapsed Get the second time in seconds Subtract first time from the second time Tell them how close to 10 the answer was. Extension Sometimes this solution doesn't work. Can you work out why it doesn’t work? Can you fix it? Hint Use Now.Second - To get the current time in seconds of the minute Prior Knowledge Needed How to create variables How to input data into a variable How to display variables How to use system functions. How to use system variables 19 Challenge 21 Write a program that will store names into an array. As a new name is entered it will be added to the end of the array. The user can keep adding names until they enter the dummy value ‘exit’ Once this has been done the program will display any duplicate names. E.g. Enter name: Bill Enter name: Mary Enter name: Anisha Enter name: Mary Enter name: exit Mary is a duplicate. Extension Display how many times each name has been duplicated Prior Knowledge Needed How to create a Nested FOR loop structure. Using arrays
- 7. 18 Challenge 20 Create a Fibonacci sequence generator. (The Fibo- nacci sequence was originally used as a basic model for rabbit population growth). The Fibonacci se- quence goes like this. 0,1,1,2,3,5,8,13 The Nth term is the sum of the previous two terms. So in the example above the next term would be 21 because it would be the previous two terms added together (8+13). You will need create a list of Fibonnaci numbers up to the 50th term. The program will then ask the user for which position in the se- quence they want to know the Fibonacci value for (up to 50). E.g Which position in sequence? 6 (start counting at 0) Fibonacci number is 8 Hint You will need to store the sequence in an array of Long (these numbers can get pretty big!) Prior Knowledge Needed How to create a FOR loop struc- ture. Using arrays 7 Challenge 7 Extend the program in Challenge 5 to make a game for seeing how quick people are at typ- ing the alphabet. Algorithm Tell them to hit enter key when ready Get the first time in seconds (and minutes) Get them to type in the alphabet and hit enter Get the second time in seconds (and minutes) Check they have entered the alphabet correctly If they entered it correctly then Subtract first time from the second time Tell them how many seconds they took Extension Keep a record of the best time achieved. Deal with upper or lower case let- ters entered Hint You’ll need to store their attempt at the alphabet in a variable and compare with “abcdef...” Prior Knowledge Needed As challenge 5 plus.. How to write an IF statement.
- 8. 8 Challenge 9 Write a program that will generate a random playing card e.g. ‘9 Hearts’, ‘Queen Spades’ when the return key is pressed. Rather than generate a random number from 1 to 52. Create two random num- bers – one for the suit and one for the card. Extension Make a loop structure so playing cards can keep being generated Prior Knowledge Needed How to create IF or CASE state- ments with logical operators . How to generate random num- bers Challenge 8 Write a program that will accept someone’s date of birth and work out whether they can vote (i.e. Are they 18?) Prior Knowledge Needed How to create IF statement. Using the dateDiff function 17 Challenge 19 Continued... The Ceaser algorithms may have fooled the Gauls but it doesn't take a genius to crack. So a much better algorithm would be one that has a different offset for every letter. We can do this using the random number generator—because it generates the same se- quence of random numbers from a ‘seed’ position. As long as sender and receiver agree where to ‘seed’ (this will be the encryp- tion key) they can both work out the same offsets. Algorithm for encrypt function function Encrypt(text, key) Randomize(key) For each letter in text Get its ascii code Add random offset int(rnd()*10) to ascii code Turn this new ascii code back to a character Append character to ciphertext string End for return ciphertext end Extension Try to use a single function with an extra parameter to indicate whether the text is being en- crypted or decrypted rather than having two different functions. Prior Knowledge Needed How to create IF statements. How to create a condition con- trolled loop structure. Using procedures and functions String manipulation
- 9. 16 Challenge 19 Write a program to perform a basic ‘Ceaser’ encryp- tion and decryption on text. This algorithm works by moving letters along by an ‘offset’. If the offset is 2 then b —> d, h—>j etc. Try to write two functions—One called ‘encrypt’ and one called ’decrypt’. Both will return a string. The user selects whether the wish to encrypt or decrypt. The user enters sentence to encrypt and the encryption key (i.e. How many we move the letters along—this is a smallish integer) The program responds with the encrypted or decrypted version Algorithm for encryption Type in text Type in encryption key Display Encrypt(text, key) function Encrypt(text,key) For each letter in text Get its ascii code Add the key to the ascii code Turn this new ascii code back to a character Append character to ciphertext string End for return ciphertext end Hints To get a single character from a string of characters just add position in brackets after string name. Text=“Hello” Text(0)=“H” Len(Text) or Text.length will give you the number of characters in string. 9 Challenge 10 Make a game of rock, paper scissors against the computer. Algorithm Tell user to enter either rock,paper or scissors Get the response Generate a random number from 1 to 3 (1=rock,2=paper, 3=scissors) Compare user selection and computer selection Display who wins. Extension Make sure the user enters a valid entry. Add a loop structure to play several times and keep a running score Make an enumerated variable type to store choices. Prior Knowledge Needed How to create IF statements with logical operators (or nested Ifs) How to generate random num- bers Hint Don’t forget to randomize!
- 10. 10 Challenge 11 Write a program that will give the students the answer to logic gate questions e.g. Enter logic gate : OR Enter first input : 1 Enter second input :0 Result = 1 It should work for the logic gates OR, AND and XOR Extension Include NAND and NOR gates Challenge 12 Write a program that will display all the factors of a number, en- tered by the user, that are bigger than 1. (e.g. the factors of the number 12 are 6,4,3 and 2 because they di- vide into 12 exactly). Hint to find out whether a number X is a factor of Y use : IF Y mod X =0 (there is nothing remaining when Y is divided by X) Extension Tell the user if the number they entered is a prime number Prior Knowledge Needed How to create IF statements How to create a loop structure Prior Knowledge Needed How to create IF statements using logical operators 15 Challenge 18 Write a procedure(sub) drawstars that will draw a sequence of spaces followed by a sequence of stars. It should accept two pa- rameters—the number of spaces and the number of stars. E.g Drawstars(3,5) would produce _ _ _ * * * * * ( _ indicates a space!) Use your procedure to draw * * * * * * * * * * * * * * * * * * * * * * * * * * Extension Now write a program using this procedure that will draw a pyra- mid whose base is a width specified by the user. E.g. Enter base size of pyramid : 5 * *** ***** (assume the user has to enter an odd number) Prior Knowledge Needed How to create procedures How to use parameters
- 11. 14 Challenge 17 Write a function that will convert a UMS score into a grade. The function will return ‘A’—> ‘U’. The function will require a parameter to do its job: the mark The formula for AS level is >=80% —>‘A’, >=70%—>‘B’, >=60%—>‘C’ etc. Assume the maximum module mark is 100 Having written the function we want to use it three times. Write a program with the function that allows the user to enter two module AS scores and displays the grade. It then adds the two results together and displays the students overall grade. E.g. Enter Module 1 result: 78 Enter Module 1 result: 67 Result Module 1 : B Module 2: C AS Level : B Extension Allow a maximum mark other than 100. This will require the user to enter both the mark and maximum possible for that module. The function will also require the maximum mark in order to cal- culate the grade so another parameter will be needed. Prior Knowledge Needed How to create functions How to use parameters 11 Challenge 13 Write a program for a game where the computer generates a random starting number between 20 and 30. The player and the computer can remove 1,2 or 3 from the num- ber in turns. Something like this... Starting number : 25 How many do you want to remove? 3 22 left Computer removes 2 20 left The player who has to remove the last value to bring the number down to 0 is the loser. 1 left Computer removes 1 You win! Easy option Get the computer to choose a number between 1—3 at random Harder option Get the computer to employ a strategy to try and win Prior Knowledge Needed How to generate random num- bers. How to create IF statements How to create a loop structure
- 12. 12 Challenge 14 Write a program for a Higher / Lower guessing game The computer randomly generates a sequence of up to 10 num- bers between 1 and 13. The player each after seeing each number in turn has to decide whether the next number is higher or lower. If you can remember Brucie’s ‘Play your cards right’ it’s basically that. If you get 10 guesses right you win the game. Starting number : 12 Higher(H) or lower(L)? L Next number 8 Higher(H) or lower(L)? L Next number 11 You lose Hints Use a condition controlled loop (do until, while etc) to control the game. Do not find yourself repeating the same code over and over! You don't need to remember all 10 numbers just the current num- ber /next number. Don’t forget you’ll have to keep a count of the number of turns they’ve had. Extensions Give the players two lives Make sure only H or L can be entered Prior Knowledge Needed How to create IF statements. How to create a condition controlled loop structure. 13 Challenge 15 Write a program to count the number of words in a sentence. The user enters a sentence. The program responds with the number of words in the sentence. Hint Look for spaces and full stops in the string. Extension Develop a program that will display a sentence backwards after entered. Challenge 16 Guess the number game. The computer selects a random number between 1 and 100. The user keeps guessing which number the computer has chosen until they get it right. The computer responds ‘got it’ or ‘too high’ or ‘too low’ after each guess. After the user has guessed the number the computer tells them how many attempts they have made. Extension- Reverse the game. You think of a number. Get the computer to guess a number and you respond with too high(H), too low(L) or got it(G). Make sure the computer has a game plan—don't just let it guess at random! Prior Knowledge Needed How to use string manipulation func- tions Using loops and selection