🚀 Programming Example

C Program to Check Armstrong Number

👁 675 Views

💻 Practical Program

📘 Step Learning

Check Armstrong Number. To understand this example, you should have the knowledge of the following C programming topics:

C if...else Statement
C while and do...while Loop

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

abcd... = aⁿ + bⁿ + cⁿ + dⁿ +

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

📌 Information & Algorithm

Know More about Armstrong Number from this link.

💻 Program Code

#include <stdio.h>
int main() {
    int num, originalNum, remainder, result = 0;
    printf("Enter a three-digit integer: ");
    scanf("%d", &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)
        printf("%d is an Armstrong number.", num);
    else
        printf("%d is not an Armstrong number.", num);

    return 0;
}

🖥 Program Output

Enter a three-digit integer: 371
371 is an Armstrong number.

📘 Explanation

Check Armstrong Number of n digits



#include <math.h>
#include <stdio.h>

int main() {
   int num, originalNum, remainder, n = 0;
   float result = 0.0;

   printf("Enter an integer: ");
   scanf("%d", &num);

   originalNum = num;

   // store the number of digits of num in n
   for (originalNum = num; originalNum != 0; ++n) {
       originalNum /= 10;
   }

   for (originalNum = num; originalNum != 0; originalNum /= 10) {
       remainder = originalNum % 10;

      // store the sum of the power of individual digits in result
      result += pow(remainder, n);
   }

   // if num is equal to result, the number is an Armstrong number
   if ((int)result == num)
    printf("%d is an Armstrong number.", num);
   else
    printf("%d is not an Armstrong number.", num);
   return 0;
}

Output


 Enter an integer: 1634
1634 is an Armstrong number.

In this program, the number of digits of an integer is calculated first and stored in?n. And, the?pow()?function is used to compute the power of individual digits in each iteration of the second?for?loop.

🎯 How to learn from this example

First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.

🔥 Practice suggestion

Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.