Lesson 6.5. Exercices on loops in C

Exercise 1

Write a program that displays all the combinations of two 6-sided dice:

die1=1 die2=1
die1=1 die2=2
die1=1 die2=3
die1=1 die2=4
die1=1 die2=5
die1=1 die2=6
die1=2 die2=1
die1=2 die2=2
die1=2 die2=3
...

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

Exercise 2

Write a program that displays the ASCII table from 32 to 127. For each character, the program displays the ASCII code in decimal and hexadecimal:

┏━━━━━━━━━━━━━━━━┓
┃    ASCII TABLE    ┃
┗━━━━━━━━━━━━━━━━┛
| DEC | HEX | ASCII |
|-----|-----|-------|
|  32 |  20 |       |
|  33 |  21 |   !   |
|  34 |  22 |   "   |
|  35 |  23 |   #   |
|  36 |  24 |   $   |
|  37 |  25 |   %   |
|  38 |  26 |   &   |
|  39 |  27 |   '   |
|  40 |  28 |   (   |
|  41 |  29 |   )   |
|  42 |  2a |   *   |
|  43 |  2b |   +   |
|  44 |  2c |   ,   |

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

Exercise 3

Write a program that displays a rectangle of side WIDTH x HEIGHT with characters. WIDTH and HEIGHT are constants :

#define   WIDTH     16
#define   HEIGHT    3

Here is an example with the values defined above:

***************
***************
***************

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

Exercise 4

Write a program that displays a triangle according to the example below:

*******
 ******
  *****
   ****
    ***
     **
      *

The size of the triangle is defined by a constant WIDTH. In the example above, WIDTH is 7.

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

Exercise 5

Write a program that displays all the divisors of an integer entered by the user:

Enter a positive number: 30
1 is a divisor of 30
2 is a divisor of 30
3 is a divisor of 30
5 is a divisor of 30
6 is a divisor of 30
10 is a divisor of 30
15 is a divisor of 30
30 is a divisor of 30

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

Exercise 6

Write a program that displays all the possible draws of the lotto (5 balls numbered from 1 to 49). Be careful, it is not a non-repeating draw, each ball can appear only once in each draw.

 1  2  3  4  5
 1  2  3  4  6
 1  2  3  4  7
 1  2  3  4  8
 1  2  3  4  9
 1  2  3  4 10
 1  2  3  4 11
 1  2  3  4 12
 1  2  3  4 13
 1  2  3  4 14
 1  2  3  4 15
 1  2  3  4 16
 1  2  3  4 17
 1  2  3  4 18
 1  2  3  4 19
 1  2  3  4 20
 1  2  3  4 21
 1  2  3  4 22
 1  2  3  4 23

Do you realize that if this program works properly, it will display the next winning lottery draw? 😁 🤑

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

Exercise 7

Fizz-Buzz is a game in which players take turns counting. But when a player has to say a multiple of 3, they replace it with Fizz. If it's a multiple of 5, they replace it with Buzz. If it is a multiple of 3 and 5, he must say Fizz-Buzz. Write a program that displays the sequence of the game for the first 100 numbers:

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
Fizz-Buzz
16
17

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

This exercise is a test used in job interviews. It allows to estimate the ability of a developer to code cleanly. There are several ways to program this game. In the answer key, readability has been chosen, but this solution is not optimal because it repeats the same tests several times. The following video details the evolution from a naive solution to a more elegant solution. Note that the final solution in the video is not C-compliant. However, the thought process is still interesting.

Exercise 8

Write a program that asks the user to enter a positive integer. The program then displays this number in Roman numerals:

Enter a positive integer: 2022
2022 is written MMXXII in Roman numerals.

The solution presented below was written by Maxime JOMEAU, whom I thank for his work.

#include <stdio.h> int main(void) { // EVERYTHING IS TO BE DONE. return 0; }

See also

• Learn C programming
• Lesson 1.1. History of C programming language
• Lesson 1.2. First program
• Lesson 1.3. Compilation
• Lesson 1.4. Preprocessor directives
• Lesson 1.5. Which compiler to choose?
• Lesson 1.6. Flowchart
• Lesson 2.1. Types and variables
• Lesson 2.2. Integers
• Lesson 2.3. Floating point numbers
• Lesson 2.4. Characters
• Lesson 2.5. Variables initialization
• Lesson 2.6. Ariane flight 501
• Lesson 3.1. Arithmetic operators
• Lesson 3.2. modulo
• Lesson 3.3. Operators and types
• Lesson 3.4. Type casting
• Lesson 3.5. Bitwise operators
• Lesson 3.6. Bitwise operators details
• Lesson 3.7. Shifting operators
• Lesson 3.8. Assignment operators
• Lesson 3.9. Increment and decrement operators
• Lesson 3.10. Comparison operators
• Lesson 3.11. Logical operators
• Lesson 3.12. Operator precedence
• Lesson 4.1. printf
• Lesson 4.2. scanf
• Lesson 4.3. putchar
• Lesson 5.1. Conditional branching (if...else)
• Lesson 5.2. Nested if and indentation
• Lesson 5.3. Checking intervals
• Lesson 5.4. Ternary Operator ?:
• Lesson 5.5. switch..case statement
• Lesson 5.6. Break keyword in switch..case
• Lesson 6.1. do..while loop in C
• Lesson 6.2. While loop in C
• Lesson 6.3. For loop in C
• Lesson 6.4. How to choose the right loop in C ?
• Lesson 7.1. Bit masking
• Lesson 7.2. Bit masking, how to clear a bit in C?
• Lesson 7.3. Bit masking, how to set a bit in C?
• Lesson 7.4. Bit masking, how to toggle a bit in C?
• Lesson 7.5. Bit masking, how to check a single bit in C?
• Lesson 7.6. Overview of bit masking
• Lesson 8.1. Basic syntax of C functions
• Lesson 8.2. Calling C functions
• Lesson 8.3. Void keyword
• Lesson 8.4. Return keyword
• Lesson 8.5. Variable scope
• Lesson 8.6. Global variables
• Lesson 8.7. Static variables
• Lesson 8.8. Random numbers in C
• Lesson 8.9. Mathematical functions in C
• Lesson 9.1. Syntax of C arrays
• Lesson 9.2. Array initialization
• Lesson 9.3. Multidimensional arrays
• Lesson 9.4. How C arrays are stored in memory?
• Lesson 9.5. Arrays and functions
• Lesson 9.6. Exercises on C arrays
• Lesson 10.1. Strings in C
• Lesson 10.2. Null terminated string
• Lesson 10.3. The string.h library
• Lesson 10.4. String and functions
• Lesson 11.1. Introduction to pointers in C
• Lesson 11.2. Syntax of C pointers
• Lesson 11.3. Dynamic memory allocation
• Lesson 11.4. Incrementing pointers
• Lesson 11.5. Pointers as function argument in C
• Lesson 12.1. Introduction to structures in C
• Lesson 12.2. Properties of structures in C
• Lesson 12.3. Structures and pointers
• Lesson 12.4. Structures and functions
• Lesson 13.1. Recursive functions in C
• Lesson 13.2. Depth of recursive functions
• Lesson 13.2. Mutual recursion
• Lesson 14.1. Additional exercises

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