Example: Check Armstrong Number in C

// Check Armstrong Number
#include <stdio.h>
#include <math.h> // Required for pow()

// Function to check if a number is an Armstrong number
int isArmstrong(int num) {
    int originalNum, remainder, n = 0;
    double result = 0.0;

    // Step 1: Store the original number
    originalNum = num;

    // Step 2: Count the number of digits (n)
    // For single digit numbers, the power is 1.
    // For multi-digit numbers, count the digits
    int tempNum = num;
    while (tempNum != 0) {
        tempNum /= 10;
        n++;
    }

    // Handle case for 0 (0 is technically an Armstrong number)
    if (num == 0) return 1;
    // Special handling for n=0 (when num was 0), set to 1 for correct power calc
    if (n == 0) n = 1;

    // Step 3: Calculate the sum of nth powers of its digits
    tempNum = num; // Reset tempNum to the original number for digit extraction
    while (tempNum != 0) {
        remainder = tempNum % 10; // Get the last digit
        result += pow(remainder, n); // Add digit raised to the power of n
        tempNum /= 10; // Remove the last digit
    }

    // Step 4: Compare the result with the original number
    if ((int)result == originalNum) {
        return 1; // Armstrong number
    } else {
        return 0; // Not an Armstrong number
    }
}

int main() {
    int number = 153; // Example number
    if (isArmstrong(number)) {
        printf("%d is an Armstrong number.\n", number);
    } else {
        printf("%d is not an Armstrong number.\n", number);
    }

    number = 123; // Another example
    if (isArmstrong(number)) {
        printf("%d is an Armstrong number.\n", number);
    } else {
        printf("%d is not an Armstrong number.\n", number);
    }
    return 0;
}