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C program to check whether a number is armstrong number or not



C program to check whether a number is armstrong number or not

Write a C program to input a number from user and check whether given number is Armstrong number or not. How to check Armstrong numbers in C program.

What is Armstrong number?

An Armstrong number is a n-digit number that is equal to the sum of the nth power of its digits. For example -
6 = 6^1 = 6
371 = 3^3 + 7^3 + 1^3 = 371

    Input a number from user. Store it in some variable say j. Make a temporary copy of the value to some another variable for calculation purposes, say originalNum = j.
    Count total digits in the given number, store result in a variable say digits.
    Initialize another variable to store the sum of power of its digits ,say sum = 0.
    Run a loop till j > 0. The loop structure should look like while(j > 0).
    Inside the loop, find last digit of j. Store it in a variable say lastDigit = j % 10.
    Now comes the real calculation to find sum of power of digits. Perform sum = sum + pow(lastDigit, digits).
    Since the last digit of j is processed. Hence, remove last digit by performing j = j / 10.
    After loop check if(originalNum == sum), then it is Armstrong number otherwise not.

/**
 * C program to check Armstrong number
 */
#include <stdio.h>
#include <math.h>

int main()
{
    int originalNum, j, lastDigit, digits, sum;

    /* Input number from user */
    printf("Enter any number to check Armstrong number: ");
    scanf("%d", &j);

    sum = 0;

    /* Copy the value of j for processing */
    originalNum = j;

    /* Find total digits in j */
    digits = (int) log10(j) + 1;

    /* Calculate sum of power of digits */
    while(j > 0)
    {
        /* Extract the last digit */
        lastDigit = j % 10;

        /* Compute sum of power of last digit */
        sum = sum + round(pow(lastDigit, digits));

        /* Remove the last digit */
        j = j / 10;
    }

    /* Check for Armstrong number */
    if(originalNum == sum)
    {
        printf("%d is ARMSTRONG NUMBER", originalNum);
    }
    else
    {
        printf("%d is NOT ARMSTRONG NUMBER", originalNum);
    }

    return 0;
}