﻿ C programming exercises: For Loop - w3resource

# C Programming Exercises, Practice, Solution : For Loop

## C For Loop [61 exercises with solution]

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1. Write a program in C to display the first 10 natural numbers.
Expected Output :
1 2 3 4 5 6 7 8 9 10
Click me to see the solution

2. Write a C program to compute the sum of the first 10 natural numbers.
Expected Output :
The first 10 natural number is :
1 2 3 4 5 6 7 8 9 10
The Sum is : 55
Click me to see the solution

3. Write a program in C to display n terms of natural numbers and their sum.
Test Data : 7
Expected Output :
The first 7 natural number is :
1 2 3 4 5 6 7
The Sum of Natural Number upto 7 terms : 28
Click me to see the solution

4. Write a program in C to read 10 numbers from the keyboard and find their sum and average.
Test Data :
Input the 10 numbers :
Number-1 :2
...
Number-10 :2
Expected Output :
The sum of 10 no is : 55
The Average is : 5.500000
Click me to see the solution

5. Write a program in C to display the cube of the number up to an integer.
Test Data :
Input number of terms : 5
Expected Output :
Number is : 1 and cube of the 1 is :1
Number is : 2 and cube of the 2 is :8
Number is : 3 and cube of the 3 is :27
Number is : 4 and cube of the 4 is :64
Number is : 5 and cube of the 5 is :125
Click me to see the solution

6. Write a program in C to display the multiplication table for a given integer.
Test Data :
Input the number (Table to be calculated) : 15
Expected Output :
15 X 1 = 15
...
...
15 X 10 = 150
Click me to see the solution

7. Write a program in C to display the multiplier table vertically from 1 to n.
Test Data :
Input upto the table number starting from 1 : 8
Expected Output :
Multiplication table from 1 to 8
1x1 = 1, 2x1 = 2, 3x1 = 3, 4x1 = 4, 5x1 = 5, 6x1 = 6, 7x1 = 7, 8x1 = 8
...
1x10 = 10, 2x10 = 20, 3x10 = 30, 4x10 = 40, 5x10 = 50, 6x10 = 60, 7x10 = 70, 8x10 = 80
Click me to see the solution

8. Write a C program to display the n terms of odd natural numbers and their sum.
Test Data
Input number of terms : 10
Expected Output :
The odd numbers are :1 3 5 7 9 11 13 15 17 19
The Sum of odd Natural Number upto 10 terms : 100
Click me to see the solution

9. Write a program in C to display a pattern like a right angle triangle using an asterisk.

The pattern like :

```*
**
***
****
```

Click me to see the solution

10. Write a C program to display a pattern like a right angle triangle with a number.

The pattern like :

```1
12
123
1234
```

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11. Write a program in C to make such a pattern like a right angle triangle with a number which will repeat a number in a row.

The pattern like :

``` 1
22
333
4444
```

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12. Write a program in C to make such a pattern like a right angle triangle with the number increased by 1.

The pattern like :

```   1
2 3
4 5 6
7 8 9 10
```

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13. Write a program in C to make a pyramid pattern with numbers increased by 1.

```   1
2 3
4 5 6
7 8 9 10
```
Click me to see the solution

14. Write a C program to make such a pattern as a pyramid with an asterisk.

```   *
* *
* * *
* * * *
```

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15. Write a C program to calculate the factorial of a given number.
Test Data :
Input the number : 5
Expected Output :
The Factorial of 5 is: 120
Click me to see the solution

16. Write a C program to display the sum of n terms of even natural numbers.
Test Data :
Input number of terms : 5
Expected Output :
The even numbers are :2 4 6 8 10
The Sum of even Natural Number upto 5 terms : 30
Click me to see the solution

17. Write a C program to make such a pattern like a pyramid with a number which will repeat the number in the same row.

```   1
2 2
3 3 3
4 4 4 4
```

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18. Write a program in C to find the sum of the series [ 1-X^2/2!+X^4/4!- .........].
Test Data :
Input the Value of x :2
Input the number of terms : 5
Expected Output :
the sum = -0.415873
Number of terms = 5
value of x = 2.000000
Click me to see the solution

19. Write a program in C to display the n terms of a harmonic series and their sum.
1 + 1/2 + 1/3 + 1/4 + 1/5 ... 1/n terms
Test Data :
Input the number of terms : 5
Expected Output :
1/1 + 1/2 + 1/3 + 1/4 + 1/5 +
Sum of Series upto 5 terms : 2.283334
Click me to see the solution

20. Write a C program to display the pattern as a pyramid using asterisks, with each row containing an odd number of asterisks.

```   *
***
*****
```

Click me to see the solution

21. Write a program in C to display the sum of the series [ 9 + 99 + 999 + 9999 ...].
Test Data :
Input the number or terms :5
Expected Output :
9 99 999 9999 99999
The sum of the saries = 111105
Click me to see the solution

22. Write a program in C to print Floyd's Triangle.

```1
01
101
0101
10101
```
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23. Write a program in C to find the sum of the series [x - x^3 + x^5 + ......].
Test Data :
Input the value of x :3
Input number of terms : 5
Expected Output :
The sum is : 16.375000
Click me to see the solution

24. Write a program in C to find the sum of the series [ x - x^3 + x^5 + ......].
Test Data :
Input the value of x :2
Input number of terms : 5
Expected Output :
The values of the series:
2
-8
32
-128
512
The sum = 410
Click me to see the solution

25. Write a C program that displays the n terms of square natural numbers and their sum.
1 4 9 16 ... n Terms
Test Data :
Input the number of terms : 5
Expected Output :
The square natural upto 5 terms are :1 4 9 16 25
The Sum of Square Natural Number upto 5 terms = 55
Click me to see the solution

26. Write a program in C to find the sum of the series 1 +11 + 111 + 1111 + .. n terms.
Test Data :
Input the number of terms : 5
Expected Output :
1 + 11 + 111 + 1111 + 11111
The Sum is : 12345
Click me to see the solution

27. Write a C program to check whether a given number is a 'Perfect' number or not.
Test Data :
Input the number : 56
Expected Output :
The positive divisor : 1 2 4 7 8 14 28
The sum of the divisor is : 64
So, the number is not perfect.
Click me to see the solution

28. Write a C program to find the 'Perfect' numbers within a given number of ranges.
Test Data :
Input the starting range or number : 1
Input the ending range of number : 50
Expected Output :
The Perfect numbers within the given range : 6 28
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29. Write a C program to check whether a given number is an Armstrong number or not.
Test Data :
Input a number: 153
Expected Output :
153 is an Armstrong number.
Click me to see the solution

30. Write a C program to find the Armstrong number for a given range of number.
Test Data :
Input starting number of range: 1
Input ending number of range : 1000
Expected Output :
Armstrong numbers in given range are: 1 153 370 371 407
Click me to see the solution

31. Write a program in C to display a pattern like a diamond.

```    *
***
*****
*******
*********
*******
*****
***
*
```

Click me to see the solution

32. Write a C program to determine whether a given number is prime or not.
Test Data :
Input a number: 13
Expected Output :
13 is a prime number.
Click me to see the solution

33. Write a C program to display Pascal's triangle.
Test Data :
Input number of rows: 5
Expected Output :

```        1
1   1
1   2   1
1   3   3   1
1   4   6   4   1
```
Click me to see the solution

34. Write a program in C to find the prime numbers within a range of numbers.
Test Data :
Input starting number of range: 1
Input ending number of range : 50
Expected Output :
The prime number between 1 and 50 are :
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47
Click me to see the solution

35. Write a program in C to display the first n terms of the Fibonacci series.
Fibonacci series 0 1 2 3 5 8 13 .....
Test Data :
Input number of terms to display : 10
Expected Output :
Here is the Fibonacci series upto to 10 terms :
0 1 1 2 3 5 8 13 21 34
Click me to see the solution

36. Write a C program to display a such a pattern for n rows using a number that starts with 1 and each row will have a 1 as the first and last number.

```  1
121
12321
```
Click me to see the solution

37. Write a program in C to display the number in reverse order.
Test Data :
Input a number: 12345
Expected Output :
The number in reverse order is : 54321
Click me to see the solution

38. Write a C program to check whether a number is a palindrome or not.
Test Data :
Input a number: 121
Expected Output :
121 is a palindrome number.
Click me to see the solution

39. Write a program in C to find the number and sum of all integers between 100 and 200 which are divisible by 9.
Expected Output :
Numbers between 100 and 200, divisible by 9 :
108 117 126 135 144 153 162 171 180 189 198
The sum : 1683
Click me to see the solution

40. Write a C program to display the pyramid pattern using the alphabet.

```        A
A B A
A B C B A
A B C D C B A
```

Click me to see the solution

41. Write a program in C to convert a decimal number into binary without using an array.
Test Data :
Input a decimal number: 25
Binary number equivalent to said decimal number is: 0000000000000000000000000001 1001
Click me to see the solution

42. Write a C program to convert a binary number into a decimal number without using array, function and while loop.
Test Data :
Input a binary number :1010101
Expected Output :
The Binary Number : 1010101
The equivalent Decimal Number : 85
Click me to see the solution

43. Write a C program to find the HCF (Highest Common Factor) of two numbers.
Test Data :
Input 1st number for HCF: 24
Input 2nd number for HCF: 28
Expected Output :
HCF of 24 and 28 is : 4
Click me to see the solution

44. Write a C program to find the LCM of any two numbers using HCF.
Test Data :
Input 1st number for LCM: 15
Input 2nd number for LCM: 20
Expected Output :
The LCM of 15 and 20 is : 60
Click me to see the solution

45. Write a program in C to find the LCM of any two numbers.
Test Data :
Input 1st number for LCM: 15
Input 2nd number for LCM: 20
Expected Output :
The LCM of 15 and 20 is : 60
Click me to see the solution

46. Write a C program to convert a binary number into a decimal number using the math function.
Test Data :
Input the binary number :1010100
Expected Output :
The Binary Number : 1010100
The equivalent Decimal Number is : 84
Click me to see the solution

47. Write a C program to check whether a number is a Strong Number or not.
Test Data :
Input a number to check whether it is Strong number: 15
Expected Output :
15 is not a Strong number.
Click me to see the solution

48. Write a C program to find Strong Numbers within a range of numbers.
Test Data :
Input starting range of number : 1
Input ending range of number: 200
Expected Output :
The Strong numbers are :
1 2 145
Click me to see the solution

49. Write a C program to find the sum of an A.P. series.
Test Data :
Input the starting number of the A.P. series: 1
Input the number of items for the A.P. series: 10
Input the common difference of A.P. series: 4
Expected Output :
The Sum of the A.P. series are :
1 + 5 + 9 + 13 + 17 + 21 + 25 + 29 + 33 + 37 = 190
Click me to see the solution

50. Write a program in C to convert a decimal number into octal without using an array.
Test Data :
Enter a number to convert : 79
Expected Output :
The Octal of 79 is 117.
Click me to see the solution

51. Write a C program to convert an octal number to a decimal without using an array.
Test Data :
Input an octal number (using digit 0 - 7) :745
Expected Output :
The Octal Number : 745
The equivalent Decimal Number : 485
Click me to see the solution

52. Write a C program to find the sum of the G.P. series.
Test Data :
Input the first number of the G.P. series: 3
Input the number or terms in the G.P. series: 5
Input the common ratio of G.P. series: 2
Expected Output :
The numbers for the G.P. series:
3.000000 6.000000 12.000000 24.000000 48.000000
The Sum of the G.P. series : 93.000000
Click me to see the solution

53. Write a C program to convert a binary number to octal.
Test Data :
Input a binary number :1001
Expected Output :
The Binary Number : 1001
The equivalent Octal Number : 11
Click me to see the solution

54. Write a program in C to convert an octal number into binary.
Test Data :
Input an octal number (using digit 0 - 7) :57
Expected Output :
The Octal Number : 57
The equivalent Binary Number : 101111

Click me to see the solution

55. Write a C program to convert a decimal number to hexadecimal.
Test Data :
Input any Decimal number: 79
Expected Output :
The equivalent Hexadecimal Number : 4F
Click me to see the solution

56. Write a program in C to check whether a number can be expressed as the sum of two prime.
Test Data :
Input a positive integer: 16
Expected Output :
16 = 3 + 13
16 = 5 + 11
Click me to see the solution

57. Write a C program to print a string in reverse order.
Test Data :
Input a string to reverse : Welcome
Expected Output :
Reversed string is: emocleW
Click me to see the solution

58. Write a C program to find the length of a string without using the library function.
Test Data :
Input a string : welcome
Expected Output :
The string contains 7 number of characters.
So, the length of the string welcome is : 7
Click me to see the solution

59. Write a C program to check the Armstrong number of n digits.
Test Data :
Input an integer : 1634
Expected Output :
1634 is an Armstrong number
Click me to see the solution

60. Write a C program that takes user input and counts the number of characters until the end of the file.
Test Data :
Input characters : w3resource
Expected Output :
Input characters: On Linux systems and OS X EOF is CTRL+D. For Windows EOF is CTRL+Z. Number of Characters: 10
Click me to see the solution

61. Write a C program that takes input from the user and counts the number of uppercase and lowercase letters, as well as the number of other characters.
Test Data :
Input characters : w3resource
Expected Output :
Input characters: On Linux systems and OS X EOF is CTRL+D. For Windows EOF is CTRL+Z. Uppercase letters: 0 Lowercase letters: 9 Other characters: 1
Click me to see the solution

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﻿

## C Programming: Tips of the Day

Returning an array using C

You can't return arrays from functions in C. You also can't (shouldn't) do this:

```char *returnArray(char array []){
char returned ;
//methods to pull values from array, interpret them, and then create new array
return &(returned); //is this correct?
}
```

returned is created with automatic storage duration and references to it will become invalid once it leaves its declaring scope, i.e., when the function returns.

You will need to dynamically allocate the memory inside of the function or fill a preallocated buffer provided by the caller.

Dynamically allocate the memory inside of the function (caller responsible for deallocating ret)

```char *foo(int count) {
char *ret = malloc(count);
if(!ret)
return NULL;

for(int i = 0; i < count; ++i)
ret[i] = i;

return ret;
}
```

Call it like so:

```int main() {
char *p = foo(10);
if(p) {
// do stuff with p
free(p);
}

return 0;
}
```

Ref : https://bit.ly/3yFIeao

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