# C++ For Loop: Exercises, Practice, Solution

## C++ For Loop [87 exercises with solution]

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1. Write a program in C++ to find the first 10 natural numbers.
Sample output:
The natural numbers are:
1 2 3 4 5 6 7 8 9 10
Click me to see the sample solution

2. Write a program in C++ to find the sum of the first 10 natural numbers.
Sample Output:
Find the first 10 natural numbers:
---------------------------------------
The natural numbers are:
1 2 3 4 5 6 7 8 9 10
The sum of first 10 natural numbers: 55
Click me to see the sample solution

3. Write a program in C++ to display n terms of natural numbers and their sum.
Sample Output:
Input a number of terms: 7
The natural numbers upto 7th terms are:
1 2 3 4 5 6 7
The sum of the natural numbers is: 28
Click me to see the sample solution

4. Write a program in C++ to find the perfect numbers between 1 and 500.
The perfect numbers between 1 to 500 are:
6
28
496
Click me to see the sample solution

5. Write a program in C++ to check whether a number is prime or not.
Sample Output:
Input a number to check prime or not: 13
The entered number is a prime number.
Click me to see the sample solution

6. Write a program in C++ to find a prime number within a range.
Input number for starting range: 1
Input number for ending range: 100
The prime numbers between 1 and 100 are:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
The total number of prime numbers between 1 to 100 is: 25
Click me to see the sample solution

7. Write a program in C++ to find the factorial of a number.
Sample output:
Input a number to find the factorial: 5
The factorial of the given number is: 120
Click me to see the sample solution

8. Write a program in C++ to find the last prime number that occurs before the entered number.
Sample Output:
Input a number to find the last prime number occurs before the number: 50
47 is the last prime number before 50
Click me to see the sample solution

9. Write a program in C++ to find the Greatest Common Divisor (GCD) of two numbers.
Sample Output:
Input the first number: 25
Input the second number: 15
The Greatest Common Divisor is: 5
Click me to see the sample solution

10. Write a program in C++ to find the sum of the digits of a given number.
Sample Output:
Input a number: 1234
The sum of digits of 1234 is: 10
Click me to see the sample solution

11. Write a program in C++ to find the sum of the series 1 + 1/2^2 + 1/3^3 + ..+ 1/n^n.
Sample Output:
Input the value for nth term: 5
1/1^1 = 1
1/2^2 = 0.25
1/3^3 = 0.037037
1/4^4 = 0.00390625
1/5^5 = 0.00032
The sum of the above series is: 1.29126
Click me to see the sample solution

12. Write a program in C++ to calculate the sum of the series (1*1) + (2*2) + (3*3) + (4*4) + (5*5) + ... + (n*n).
Sample Output:
Input the value for nth term: 5
1*1 = 1
2*2 = 4
3*3 = 9
4*4 = 16
5*5 = 25
The sum of the above series is: 55
Click me to see the sample solution

13. Write a program in C++ to calculate the series (1) + (1+2) + (1+2+3) + (1+2+3+4) + ... + (1+2+3+4+...+n).
Sample Output:
Input the value for nth term: 5
1 = 1
1+2 = 3
1+2+3 = 6
1+2+3+4 = 10
1+2+3+4+5 = 15
The sum of the above series is: 35
Click me to see the sample solution

14. Write a program in C++ to find the sum of series 1 - X^2/2! + X^4/4!-.... upto nth term.
Sample Output:
Input the value of X: 3
Input the value for nth term: 4
term 1 value is: 1
term 2 value is: -4.5
term 3 value is: 3.375
term 4 value is: -1.0125
The sum of the above series is: -1.1375
Click me to see the sample solution

15. Write a C++ program that asks the user to enter positive integers in order to process count, maximum, minimum, and average or terminate the process with -1.
Sample Output:
Your input is for termination. Here is the result below:
Number of positive integers is: 4
The maximum value is: 9
The minimum value is: 3
The average is 6.00
Click me to see the sample solution

16. Write a C++ program to list non-prime numbers from 1 to an upperbound.
Sample Output:
Input the upperlimit: 25
The non-prime numbers are:
4 6 8 9 10 12 14 15 16 18 20 21 22 24 25
Click me to see the sample solution

17. Write a program in C++ to print a square pattern with the # character.
Sample Output:
Print a pattern like square with # character:
--------------------------------------------------
Input the number of characters for a side: 4
# # # #
# # # #
# # # #
# # # #
Click me to see the sample solution

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

19. Write a program in C++ to display the multiplication table vertically from 1 to n.
Sample Output:
Input the number upto: 5
Multiplication table from 1 to 5
1x1=1 2x1=2 3x1=3 4x1=4 5x1=5
1x2=2 2x2=4 3x2=6 4x2=8 5x2=10
1x3=3 2x3=6 3x3=9 4x3=12 5x3=15
1x4=4 2x4=8 3x4=12 4x4=16 5x4=20
1x5=5 2x5=10 3x5=15 4x5=20 5x5=25
1x6=6 2x6=12 3x6=18 4x6=24 5x6=30
1x7=7 2x7=14 3x7=21 4x7=28 5x7=35
1x8=8 2x8=16 3x8=24 4x8=32 5x8=40
1x9=9 2x9=18 3x9=27 4x9=36 5x9=45
1x10=10 2x10=20 3x10=30 4x10=40 5x10=50
Click me to see the sample solution

20. Write a C++ program that displays the sum of n odd natural numbers.
Sample Output:
Input number of terms: 5
The odd numbers are: 1 3 5 7 9
The Sum of odd Natural Numbers upto 5 terms: 25
Click me to see the sample solution

21. Write a C++ program that displays the sum of the n terms of even natural numbers.
Sample Output:
Input number of terms: 5
The even numbers are: 2 4 6 8 10
The Sum of even Natural Numbers upto 5 terms: 30
Click me to see the sample solution

22. 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.
Sample Output:
Input number of terms: 5
1/1 + 1/2 + 1/3 + 1/4 + 1/5
The sum of the series upto 5 terms: 2.28333
Click me to see the sample solution

23. Write a program in C++ to display the sum of the series [ 9 + 99 + 999 + 9999 ...].
Sample Output:
Input number of terms: 5
9 99 999 9999 99999
The sum of the sarise = 111105
Click me to see the sample solution

24. Write a program in C++ to display the sum of the series [ 1+x+x^2/2!+x^3/3!+....].
Sample Output:
Input the value of x: 3
Input number of terms: 5
The sum is : 16.375
Click me to see the sample solution

25. Write a program in C++ to find the sum of the series [ x - x^3 + x^5 + ......].
Sample Output:
Input the value of x: 2
Input number of terms: 5
The values of series:
2
-8
32
-128
512
The sum of the series upto 5 term is: 410

Click me to see the sample solution

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

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

28. Write a program in C++ to find the number and sum of all integers between 100 and 200 which are divisible by 9.
Sample 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 sample solution

29. Write a program in C++ to find the LCM of any two numbers using HCF.
Sample Output:
Input 1st number for LCM: 15
Input 2nd number for LCM: 25
The LCM of 15 and 25 is: 75
Click me to see the sample solution

30. Write a program in C++ to display the numbers in reverse order.
Sample Output:
Input a number: 12345
The number in reverse order is : 54321
Click me to see the sample solution

31. Write a C++ program to find the sum of an A.P. series.
Sample Output:
Input the starting number of the A.P. series: 1
Input the number of items for the A.P. series: 8
Input the common difference of A.P. series: 5
The Sum of the A.P. series are :
1 + 6 + 11 + 16 + 21 + 26 + 31 + 36 = 148
Click me to see the sample solution

32. Write a C++ program to find the sum of the GP series.
Sample Output:
Input the starting number of the G.P. series: 3
Input the number of items for the G.P. series: 5
Input the common ratio of G.P. series: 2
The numbers for the G.P. series:
3 6 12 24 48
The Sum of the G.P. series: 93
Click me to see the sample solution

33. Write a program in C++ to check whether a number can be expressed as the sum of two.
Sample Output:
Input a positive integer: 20
20 = 3 + 17
20 = 7 + 13
Click me to see the sample solution

34. Write a program in C++ to find the length of a string without using the library function.
Sample Output:
Input a string: w3resource.com
The string contains 14 number of characters.
So, the length of the string w3resource.com is:14
Click me to see the sample solution

35. Write a program in C++ to display a pattern like a right angle triangle using an asterisk.
Sample Output:
Input number of rows: 5
*
**
***
****
*****
Click me to see the sample solution

36. Write a program in C++ to display the pattern like right angle triangle with number.
Sample Output:
Input number of rows: 5
1
12
123
1234
12345
Click me to see the sample solution

37. Write a C++ program that makes a pattern such as a right angle triangle using numbers that repeat.
Sample Output:

```  Input number of rows: 5
1
22
333
4444
55555 ```
Click me to see the sample solution

38. Write a C++ program to make such a pattern like a right angle triangle with the number increased by 1.
Sample Output:

``` Input number of rows: 4
1
2 3
4 5 6
7 8 9 10 ```
Click me to see the sample solution

39. Write a C++ program to make such a pattern like a pyramid with numbers increased by 1.
Sample Output:

``` Input number of rows: 4
1
2 3
4 5 6
7 8 9 10
```

Click me to see the sample solution

40. Write a C++ program to make such a pattern like a pyramid with an asterisk.
Sample Output:

``` Input number of rows: 5
*
* *
* * *
* * * *
* * * * *```
Click me to see the sample solution

41. Write a C++ program to make such a pattern, like a pyramid, with a repeating number.
Sample Output:

``` Input number of rows: 5
1
2 2
3 3 3
4 4 4 4
5 5 5 5 5
```
Click me to see the sample solution

42. Write a C++ program that displays the pattern like a pyramid using asterisks, with odd numbers in each row.
Sample Output:

```

Input number of rows: 5

*
***
*****
******* ```
Click me to see the sample solution

43. Write a C++ program to print Floyd's Triangle.
Sample Output:

``` Input number of rows: 5
1
01
101
0101
10101```
Click me to see the sample solution

44. Write a C++ program to display a pattern like a diamond.
Sample Output:

``` Input number of rows (half of the diamond): 5

*
***
*****
*******
*********
*******
*****
***
*   ```
Click me to see the sample solution

45. Write a C++ program to display Pascal's triangle like a pyramid.
Sample Output:

``` Input number of rows: 5
1
1   1
1   2   1
1   3   3   1
1   4   6   4   1 ```
Click me to see the sample solution

46. Write a C++ program to display Pascal's triangle like a right angle triangle.
Sample Output:

``` Input number of rows: 7
1
1   1
1   2   1
1   3   3   1
1   4   6   4   1
1   5   10   10   5   1
1   6   15   20   15   6   1```
Click me to see the sample solution

47. Write a program in C++ to display such a pattern for n number of rows using numbers. Odd numbers will appear in each row. The first and last number of each row will be 1 and the middle column will be the row number.
Sample Output:

```
Input number of rows: 5

1
121
12321
1234321
123454321 ```
Click me to see the sample solution

48. Write a program in C++ to display the pyramid pattern using the alphabet.
Sample Output:

``` Input the number of Letters (less than 26) in the Pyramid: 5
A
A B A
A B C B A
A B C D C B A
A B C D E D C B A```
Click me to see the sample solution

49. Write a C++ program to print a pyramid of digits as shown below for n number of lines.

```    1
232
34543
4567654
567898765
```
Sample Output:
``` Input the number of rows: 5
1
232
34543
4567654
567898765 ```
Click me to see the sample solution

50. Write a C++ program to print a pattern in which the highest number of columns appears in the first row.
Sample Output:

``` Input the number of rows: 5
12345
2345
345
45
5```
Click me to see the sample solution

51. Write a C++ program that displays the pattern with the highest columns in the first row and digits with the right justified digits.
Sample Output:

``` Input number of rows: 5
12345
1234
123
12
1 ```
Click me to see the sample solution

52. Write a C++ program to display the pattern using digits with left justified spacing and the highest columns appearing in the first row in descending order.
Sample Output:

``` Input number of rows: 5
5 4 3 2 1
4 3 2 1
3 2 1
2 1
1```
Click me to see the sample solution

53. Write a C++ program to display the pattern like right angle triangle with right justified digits.
Sample Output:

``` Input number of rows: 5
1
21
321
4321
54321```
Click me to see the sample solution

54. Write a program in C++ to display the pattern like pyramid, power of 2.
Sample Output:

```
Input the number of rows: 5
1
1  2  1
1  2  4  2  1
1  2  4  8  4  2  1
1	2  4  8  16  8  4  2  1
```
Click me to see the sample solution

55. Write a program in C++ to display such a pattern for n number of rows using numbers. There will be odd numbers in each row. The first and last number of each row will be 1 and the middle column will be the row number. N numbers of columns will appear in the 1st row.
Sample Output:

``` Input number of rows: 7
1234567654321
12345654321
123454321
1234321
12321
121
1 ```
Click me to see the sample solution

56. Write a program in C++ to find the first and last digits of a number.
Sample Output:
Input any number: 5679
The first digit of 5679 is: 5
The last digit of 5679 is: 9
Click me to see the sample solution

57. Write a program in C++ to find the sum of the first and last digits of a number.
Sample Output:
Input any number: 12345
The first digit of 12345 is: 1
The last digit of 12345 is: 5
The sum of first and last digit of 12345 is: 6
Click me to see the sample solution

58. Write a program in C++ to calculate the product of the digits of any number.
Sample Output:
Input a number: 3456
The product of digits of 3456 is: 360
Click me to see the sample solution

59. Write a program in C++ to find the frequency of each digit in a given integer.
Sample Output:
Input any number: 122345
The frequency of 0 = 0
The frequency of 1 = 1
The frequency of 2 = 2
The frequency of 3 = 1
The frequency of 4 = 1
The frequency of 5 = 1
The frequency of 6 = 0
The frequency of 7 = 0
The frequency of 8 = 0
The frequency of 9 = 0
Click me to see the sample solution

60. Write a program in C++ to input any number and print it in words.
Sample Output:
Input any number: 8309
Eight Three Zero Nine
Click me to see the sample solution

61. Write a C++ program that prints all ASCII characters with their values.
Sample Output:
Input the starting value for ASCII characters: 65
Input the ending value for ASCII characters: 75
The ASCII characters:
65 --> A
66 --> B
67 --> C
68 --> D
69 --> E
70 --> F
71 --> G
72 --> H
73 --> I
74 --> J
75 --> K
Click me to see the sample solution

62. Write a program in C++ to find the power of any number using a for loop.
Sample Output:
Input the base: 2
Input the exponent: 5
2 ^ 5 = 32
Click me to see the sample solution

63. Write a program in C++ to enter any number and print all factors of the number.
Sample Output:
Input a number: 63
The factors are: 1 3 7 9 21 63
Click me to see the sample solution

64. Write a program in C++ to find the one's complement of a binary number.
Sample Output:
Input a 8 bit binary value: 10100101
The original binary = 10100101
After ones complement the number = 01011010
Click me to see the sample solution

65. Write a program in C++ to find the two's complement of a binary number.
Sample Output:
Input a 8 bit binary value: 01101110
The original binary = 01101110
After ones complement the value = 10010001
After twos complement the value = 10010010
Click me to see the sample solution

66. Write code to create a checkerboard pattern with the words "black" and "white".
Sample Output:
Input number of rows: 5
black-white-black-white-black
white-black-white-black-white
black-white-black-white-black
white-black-white-black-white
black-white-black-white-black
Click me to see the sample solution

67. Write a program in C++ to calculate the sum of the series 1.2+2.3+3.4+4.5+5.6+.......
Sample Output:
Input the last integer between 1 to 98 without fraction you want to add: 10 1.2 + 2.3 + 3.4 + 4.5 + 5.6 + 6.7 + 7.8 + 8.9 + 9.1 + 10.11 The sum of the series =59.61
Click me to see the sample solution

68. Write a program that will print the first N numbers for a specific base.
Sample Output:
Print the first N numbers for a specific base:
The number 11 in base 10 = 1*(10^1)+1*(10^0)=11
Similarly the number 11 in base 7 = 1*(7^1)+1*(7^0)=8
----------------------------------------------------------------
Input the number of term: 15
Input the base: 9
The numbers in base 9 are:
1 2 3 4 5 6 7 8 10 11 12 13 14 15 16
Click me to see the sample solution

69. Write a program in C++ to produce a square matrix with 0's down the main diagonal, 1's in the entries just above and below the main diagonal, 2's above and below that, etc.
0 1 2 3 4
1 0 1 2 3
2 1 0 1 2
3 2 1 0 1
4 3 2 1 0
Sample Output:

```
Input number or rows: 8
0  1  2  3  4  5  6  7
1  0  1  2  3  4  5  6
2  1  0  1  2  3  4  5
3  2  1  0  1  2  3  4
4  3  2  1  0  1  2  3
5  4  3  2  1  0  1  2
6  5  4  3  2  1  0  1
7  6  5  4  3  2  1  0
```
Click me to see the sample solution

70. Write a program in C++ to convert a decimal number to a binary number.
Sample Output:
Input a decimal number: 35
The binary number is: 100011
Click me to see the sample solution

71. Write a program in C++ to convert a decimal number to a hexadecimal number.
Sample Output:
Input a decimal number: 43
The hexadecimal number is : 2B
Click me to see the sample solution

72. Write a C++ program to convert a decimal number to an octal number.
Sample Output:
Input a decimal number: 15
The octal number is: 17
Click me to see the sample solution

73. Write a C++ program to convert a binary number to a decimal number.
Sample Output:
Input a binary number: 1011
The decimal number: 11
Click me to see the sample solution

74. Write a C++ program to convert a binary number to a hexadecimal number.
Sample Output:
Input a binary number: 1011
Click me to see the sample solution

75. Write a C++ program to convert a binary number to an octal number.
Sample Output:
Input a binary number: 1011
The equivalent octal value of 1011 is : 13
Click me to see the sample solution

76. Write a C++ program to convert an octal number to a decimal number.
Sample Output:
Input any octal number: 17
The equivalent decimal number: 15
Click me to see the sample solution

77. Write a C++ program to convert an octal number to a binary number.
Sample Output:
Input any octal number: 17
The equivalent binary number: 1111
Click me to see the sample solution

78. Write a C++ program to convert an octal number to a hexadecimal number.
Sample Output:
Input any octal number: 77
The hexadecimal value of 77 is: 3F
Click me to see the sample solution

79. Write a C++ program to convert a hexadecimal number to a decimal number.
Sample Output:
Input any 32-bit Hexadecimal Number: 25
The value in decimal number is: 37
Click me to see the sample solution

80. Write a C++ program to convert a hexadecimal number to a binary number.
Sample Output:
Input any 32-bit Hexadecimal Number: 5f
The equivalant binary number is: 1011111
Click me to see the sample solution

81. Write a C++ program to convert a hexadecimal number to an octal number.
Sample Output:
Input any 32-bit Hexadecimal Number: 5f The equivalant octal number is: 137
Click me to see the sample solution

82. Write a program in C++ to compare two numbers.
Sample Output:
Input the first integer: 25
Input the second integer: 15
25 != 15
25 > 15
25 >= 15
Click me to see the sample solution

83. Write a C++ program to compute the sum of the digits of an integer.
Sample Output:
Input any number: 25
The sum of the digits of the number 25 is: 7
Click me to see the sample solution

84. Write a C++ program to compute the sum of the digits of an integer using a function.
Sample Output:
Input any number: 255 The sum of the digits of the number 255 is: 12
Click me to see the sample solution

85. Write a program in C++ to reverse a string.
Sample Output:
Enter a string: w3resource The string in reverse are: ecruoser3w
Click me to see the sample solution

86. Write a C++ program to count the letters, spaces, numbers and other characters in an input string.
Sample Output:
Enter a string: This is w3resource.com
The number of characters in the string is: 22
The number of alphabets are: 18
The number of digits are: 1
The number of spaces are: 2
The number of other characters are: 1
Click me to see the sample solution

87. Write a C++ program to create and display an original three-digit numbers using 1, 2, 3, 4. Also count how many three-digit numbers are there.
Sample Output:
The three-digit numbers are:
123 124 132 134 142 143 213 214 231 234 241 243 312 314 321 324 341 342 412 413 421 423 431 432
Total number of the three-digit-number is: 24
Click me to see the sample solution

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## C++ Programming: Tips of the Day

Why is there no std::stou?

The most pat answer would be that the C library has no corresponding "strtou", and the C++11 string functions are all just thinly veiled wrappers around the C library functions: The std::sto* functions mirror strto*, and the std::to_string functions use sprintf.

Ref: https://bit.ly/3wtz2qA

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