C Program to Check Armstrong Number

Introduction

An Armstrong number (also known as a narcissistic number) is a number that is equal to the sum of its own digits raised to the power of the number of digits. For example, 153 is an Armstrong number because (1^3 + 5^3 + 3^3 = 153). Understanding how to check for Armstrong numbers in C programming is an interesting challenge that sharpens logic and mastery over loops and conditionals.

In this article, you will learn how to create a C program to determine if a number is an Armstrong number. You will explore examples that cover both basic and advanced scenarios, ensuring a solid grasp of implementing this verification method in the C programming language.

Basic Armstrong Number Check

Determine if a Single Number is an Armstrong Number

1. Read a number from the user.

2. Calculate the number of digits in the number.

3. Sum the cubes (or n-th power) of its digits.

4. Compare the sum with the original number.

   c Copy

   #include <stdio.h>
   
   int main() {
       int num, original, remainder, sum = 0;
       int n = 0;  // Number of digits
   
       printf("Enter an integer: ");
       scanf("%d", &num);
   
       original = num;
   
       // Calculate number of digits
       while (original != 0) {
           original /= 10;
           ++n;
       }
   
       original = num;
   
       // Sum the nth powers of its digits
       while (original != 0) {
           remainder = original % 10;
           int power = 1;
           for (int i = 0; i < n; i++) {
               power *= remainder;
           }
           sum += power;
           original /= 10;
       }
   
       if (sum == num)
           printf("%d is an Armstrong number.\n", num);
       else
           printf("%d is not an Armstrong number.\n", num);
   
       return 0;
   }
   

   This code snippet starts by calculating the number of digits (n) in a given number (num). It then computes the sum of each digit raised to the power of n and compares the sum to the original number to determine if it’s an Armstrong number.

Advanced Armstrong Number Check

Validate a Range of Numbers

1. Iterate over a range of numbers.

2. Implement the armstrong check for each number in the range.

3. Display the results accordingly.

   c Copy

   #include <stdio.h>
   
   int isArmstrong(int num);
   
   int main() {
       int lower, upper;
   
       printf("Enter lower bound: ");
       scanf("%d", &lower);
       printf("Enter upper bound: ");
       scanf("%d", &upper);
   
       printf("Armstrong numbers between %d and %d are: ", lower, upper);
       for (int i = lower; i <= upper; i++) {
           if (isArmstrong(i)) {
               printf("%d ", i);
           }
       }
       printf("\n");
   
       return 0;
   }
   
   int isArmstrong(int num) {
       int original = num, remainder, sum = 0;
       int n = 0;
   
       while (original != 0) {
           original /= 10;
           ++n;
       }
   
       original = num;
   
       while (original != 0) {
           remainder = original % 10;
           int power = 1;
           for (int i = 0; i < n; i++) {
               power *= remainder;
           }
           sum += power;
           original /= 10;
       }
   
       return sum == num;
   }
   

   This enhanced version defines a function isArmstrong() to check if a single number is an Armstrong number. It then iterates over a user-defined range, checking each number using the previously defined function and prints those that are Armstrong numbers.

Conclusion

The process of checking Armstrong numbers in C involves understanding loops, conditional statements, and basic mathematical operations. By implementing and iterating on the examples provided, you gain deeper insights into both C syntax and more complex programming concepts like function encapsulation and reusability. Use these techniques to further enrich your understanding of how numerical problems can be tackled effectively in C programming.