C Program to Check Armstrong Number using Function | Recursion | For loop | While loop

C program to check Armstrong number using function, recursion, for loop, and while loop.

In this article, you will learn how to make a C program to check Armstrong number using function, recursion, for loop, and while loop.

 

Example-1

 

Example-2

 

You should have knowledge of the following topics in c programming to understand this program:

• C main() function
• C printf() function
• C Function
• C Recursion
• C For loop
• C While loop
• C Math library

 

What is Armstrong Number?

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

 

In this article, we solve this problem in five methods:

1. Using the for loop
2. Using the function
3. Using the recursion
4. Using the while loop
5. Without using pow() function

 

Source Code

// C Program to Check Armstrong Number using For loop
#include <stdio.h>
#include <math.h>

int main() {
    int x, y, rem, n = 0;
    float r = 0.0;

    // x - To store the input number
    // y - To store the storage of original input number to check
    // rem - To store the reminder
    // r - To store the result variable

    printf("-----Enter the integer number-----\n");
    scanf("%d", &x);

    y = x;

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

    for (y = x; y != 0; y /= 10) {
        rem = y % 10;
        // store the sum of the power of individual digits in r
        r += pow(rem, n);
    }

    // if x is equal to r, the number is an Armstrong number
    if ((int) r == x) {
    	printf("%d is an Armstrong number.\n", x);
    } else {
    	printf("%d is not an Armstrong number.\n", x);
    }
    return 0;
}

Run Program

Output

 

Explanation

In these given programs, we have taken input 9474 a positive integer number to check it is an Armstrong or not using the for loop and while loop statement.

We applied the Armstrong number formula in these loops to check the sum of its digits' multiplication with its length is equal to the given input value.

 

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C Program to Check Armstrong Number using Function

// C Program to Check Armstrong Number using Function
#include <stdio.h>
#include <math.h>

// This function will check input number is armstrong or not
void CheckArmstrong(int x) {
    int y, rem, n = 0;
    float r = 0.0;

    // y - To store the storage of original input number to check
    // rem - To store the reminder
    // r - To store the result variable

    y = x;

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

    for (y = x; y != 0; y /= 10) {
        rem = y % 10;
        // store the sum of the power of individual digits in r
        r += pow(rem, n);
    }

    // if x is equal to r, the number is an Armstrong number
    if ((int) r == x) {
        printf("%d is an Armstrong number.\n", x);
    } else {
        printf("%d is not an Armstrong number.\n", x);
    }
}

// It's the driver function
int main() {
    int x; // To store the input number

    printf("-----Enter the integer number-----\n");
    scanf("%d", &x);

    CheckArmstrong(x);
    return 0;
}

Run Program

 

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C Program to Check Armstrong Number using Recursion

// C Program to Check Armstrong Number using Recursion
#include <stdio.h>
#include <math.h>

// This function will work recursive
float CheckArmstrong(int x, int size) {
    if (x > 0)
        return (pow( x%10, size) + CheckArmstrong(x/10, size));
}

// It's the driver function
int main() {
    int x; // To store the input number
    int y, size = 0;

    printf("-----Enter the integer number-----\n");
    scanf("%d", &x);

    y = x;

    for (y = x; y != 0; ++size) {
        y /= 10;
    }

    if ((int) CheckArmstrong(x, size) == x) {
        printf("%d is an Armstrong number.\n", x);
    } else {
        printf("%d is not an Armstrong number.\n", x);
    }
    return 0;
}

Run Program

Output

 

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C Program to Check Armstrong Number or Not using While loop

// C Program to Check Armstrong Number using While loop
#include <stdio.h>
#include <math.h>

int main() {
    int x, y, z, rem, n = 0;
    float r = 0.0;

    // x - To store the input number
    // y & z - To store the storage of original input number to check
    // rem - To store the reminder
    // r - To store the result variable

    printf("-----Enter the integer number-----\n");
    scanf("%d", &x);

    z = y = x;

    while (y != 0) {
        y /= 10;
        ++n;
    }

    while (z != 0) {
        rem = z % 10;
        r += pow(rem, n);
        z /= 10;
    }
    
    // if x is equal to r, the number is an Armstrong number
    if ((int) r == x) {
    	printf("%d is an Armstrong number.\n", x);
    } else {
    	printf("%d is not an Armstrong number.\n", x);
    }
    return 0;
}

Run Program

 

C Program to Check Armstrong Number without using pow() Function

// C Program to Check Armstrong Number without using pow() Function
#include <stdio.h>

int main() {
    int x, y, z, rem = 1, rem2 = 1, n = 0, m = 0;
    float r = 0.00;

    // x - To store the input number
    // y & z - To store the storage of original input number to check
    // rem & rem2 - To store the reminder values
    // r - To store the result variable

    printf("-----Enter the integer number-----\n");
    scanf("%d", &x);

    z = y = x;

    while (y != 0) {
        y /= 10;
        ++n;
    }

    m = n;

    while (z != 0) {
        rem = z % 10;

        rem2 = 1;
        while (n > 0) {
        	rem2 *= rem;
        	--n;
        }
        n = m;

        r += rem2;
        z /= 10;
    }
    
    // if x is equal to r, the number is an Armstrong number
    if ((int) r == x) {
    	printf("%d is an Armstrong number.\n", x);
    } else {
    	printf("%d is not an Armstrong number.\n", x);
    }
    return 0;
}

Run Program

Output

 

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