Armstrong number in C

January 25, 2023

What is an Armstrong number?

An Armstrong number in C or in any language is a number that is equal to the sum of digits that is raised to the power of number  of digits in the number. In simple terms if a three digit number is Armstrong number only if the sum of individual’s cube is equal to the original number itself.

armstrong-number

Syntax:

A general representation of Armstrong number in C
abcd... = an + bn + cn + dn +

Syntax:

Visual representation of Armstrong number with 3 digits
254 = 2*2*2 + 5*5*5 + 4*4*4

Algorithm:

  • Step 1: Start
  • Step 2: Initialize and declare the variable current_pointer, sum=0 and num=number.
  • Step 3: Read 3 digit integer input from the user.
  • Step 4:Do step 5 to 7 until num>0.
  • Step5:current_pointer=(num%10)
  • Step 6: sum=sum(current_pointer*current_pointer*current_pointer)
  • Step 7: num=number/10
  • Step 8: Check if the sum==number
  • Step 9: If true then print”The number is an Armstrong number”.
  • Step 10: Else print” Number is not an Armstrong number”.
  • Step 11: End.
C tutorial desk gif
 
 

Toggle each character in a string

Count the number of vowels

Length of the string without using strlen() function

Working:

In these program we will learn how to check if a number is Armstrong number or not.

Example 1 to check Armstrong number in C:

Program where the number is predefined and checked if it is Armstrong number or not.

Run 
#include<stdio.h>
#include<math.h>
int isArmstrong(int number)
{
    int current_digit, sum = 0, num = number, number_of_digits;
    while (num > 0)
    {
        current_digit = num % 10;
        sum = sum + pow(current_digit, 3);
        num = num / 10;
    }
    if (sum == number) 
    {
        return 1;
    } 
    else
    {
        return 0;
    }
}
int main() 
{
    int n= 371, isArmstrongNumber;
    isArmstrongNumber = isArmstrong(n);
    if (isArmstrongNumber == 1) 
    {
        printf("%d is an Armstrong Number.", n);
    } 
    else
    {
    printf("%d is not an Armstrong Number.", n);
    }
    return 0;
}

Output:

371 is an Armstrong Number.

Example 2 to check Armstrong number in C:

Program to check a three digit number taken as input from the user to check if it is Armstrong number or not.

Run 
#include<stdio.h>
int main()
{
    int n, Num, rem, result = 0;
    printf("Enter a three-digit integer: ");
    scanf("%d", &n);
    Num = n;
    while (Num != 0)
    {
        rem = Num % 10;
        result += rem * rem * rem;
        Num /= 10;
    }
    if (result == n)
        printf("%d is an Armstrong number.", n);
    else
        printf("%d is not an Armstrong number.", n);
    return 0;
}

Input:

Enter a three-digit integer: 371

Output:

371 is an Armstrong number.

Example 3 to check Armstrong number in C:

Program to check a  number taken as input from the user to check if it is Armstrong number or not.

Run 
#include<stdio.h>
#include<math.h>
int main()
{
    int n, Num, remainder, i = 0;
    float result = 0.0;
    printf("Enter an integer: ");
    scanf("%d", &n);
    Num = n;
    for (Num = n; Num != 0; ++i)
    {
        Num /= 10;
    }
    for (Num = n; Num != 0; Num /= 10) 
    {
        remainder = Num % 10;
        result += pow(remainder, i);
    }
    if ((int)result == n)
        printf("%d is an Armstrong number.", n);
    else
        printf("%d is not an Armstrong number.", n);
    return 0;
}

Input:

Enter a three-digit integer: 1634

Output:

1634 is an Armstrong number.

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