# (C++ programming Example for Beginners)

# C++ Program to Check Armstrong Number

#### In this example, you will learn to check whether a number entered by the user is an Armstrong number or not.

A positive integer is called an Armstrong number (of order n) if

abcd... = a^{n}+ b^{n}+ c^{n}+ d^{n}+ ...

In the case of an Armstrong number of 3 digits, the sum of cubes of each digit is equal to the number itself. For example, 153 is an Armstrong number because

153 = 1*1*1 + 5*5*5 + 3*3*3

## Example: Check Armstrong Number of 3 Digits

```
#include <iostream>
using namespace std;
int main(){
int num, originalNum, remainder, result = 0;
cout << "Enter a three-digit integer: ";
cin >> num;
originalNum = num;
while (originalNum != 0) {
// remainder contains the last digit
remainder = originalNum % 10;
result += remainder * remainder * remainder;
// removing last digit from the orignal number
originalNum /= 10;
}
if (result == num)
cout << num << " is an Armstrong number.";
else
cout << num << " is not an Armstrong number.";
return 0;
}
```

**Output**

Enter a positive integer: 371 371 is an Armstrong number.

In the program, we iterate through the while loop until `originalNum` is 0.

In each iteration of the loop, the cube of the last digit of `orignalNum` is added to `result`.

```
remainder = originalNum % 10;
result += remainder * remainder * remainder;
```

And, the last digit is removed from the `orignalNum`

.

When the loop ends, the sum of the individual digit’s cube is stored in `result`.

## Example: Check Armstrong Number of n Digits

```
#include <cmath>
#include <iostream>
using namespace std;
int main(){
int num, originalNum, remainder, n = 0, result = 0, power;
cout << "Enter an integer: ";
cin >> num;
originalNum = num;
while (originalNum != 0) {
originalNum /= 10;
++n;
}
originalNum = num;
while (originalNum != 0) {
remainder = originalNum % 10;
// pow() returns a double value
// round() returns the equivalent int
power = round(pow(remainder, n));
result += power;
originalNum /= 10;
}
if (result == num)
cout << num << " is an Armstrong number.";
else
cout << num << " is not an Armstrong number.";
return 0;
}
```

**Output**

Enter an integer: 1634 1634 is an Armstrong number.

In this program, the number of digits of the entered number is calculated first and stored in `n`.

And, the `pow()`

function computes the power of individual digits in each iteration of the `while`

loop.

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