Armstrong Number in C++ using For loop | Function | Class | Recursion

Armstrong number in C++ using For loop, Function, Class, and Recursion.

In this article, you will learn how to check Armstrong number in C++ using for loop, function, class, and recursion.

 

Example-1

 

Example-2

 

Armstrong Number

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

 

You should have knowledge of the following topics in c++ programming to understand these programs:

• C++ cmath library
• C++ main() function
• C++ for loop statement
• C++ while loop statement
• C++ if-else condition statement
• C++ cin object
• C++ cout object

 

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

1. Using the For loop
2. Using the Function
3. Using the Class and Object
4. Using the Recursion
5. Using the While loop
6. Without using the pow() function

Armstrong Number in C++ using For loop

// Armstrong Number in C++ using For loop
#include <iostream>
#include <cmath>
using namespace std;

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

    cout << "-----Enter the integer number-----\n";
    cin >> 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) {
        cout << x << " is an Armstrong number.\n";
    } else {
        cout << x << " is not an Armstrong number.\n";
    }
    return 0;
}

Run Program

Output

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Armstrong Number in C++ using Function

// Armstrong Number in C++ using Function
#include <bits/stdc++.h>
#include <cmath>
using namespace std;

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

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

    q = p;

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

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

    // if "p" is equal to "r", the number is an Armstrong number
    if ((int) r == p) {
        cout << p << " is an Armstrong number.\n";
    } else {
        cout << p << " is not an Armstrong number.\n";
    }
}

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

    cout << "-----Enter the integer number-----\n";
    cin >> x;

    // It will produce the final output
    CheckArmstrong(x);
    
    return 0;
}

Run Program

 

Explanation

In this given program, we have taken input 407 a positive integer number to check if it is an Armstrong or not using the for loop and pow() function.

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

Then It will return the final output of the program whether the input number is Armstrong or Not.

---

Armstrong Number in C++ using Class and Object

// Armstrong Number in C++ using Class and Object
#include <bits/stdc++.h>
#include <cmath>
using namespace std;

class Armstrong {
public:
    int p;
    float r = 0.00;

    // This method will check input number is Armstrong or not
    void CheckArmstrong(int x)
    {
        p = x;
        int q, rem, n = 0;

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

        q = p;

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

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

    // This method will print the final output of the program
    void ArmstrongNumber()
    {
        // if "p" is equal to "r", the number is an Armstrong number
        if ((int) r == p)
            cout << p << " is an Armstrong number.\n";
        else
            cout << p << " is not an Armstrong number.\n";
    }
};

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

    cout << "-----Enter the integer number-----\n";
    cin >> x;

    // It will create the instance of the `Armstrong` class
    Armstrong AM;

    // It will produce the final output
    AM.CheckArmstrong(x);
    AM.ArmstrongNumber();
    
    return 0;
}

Run Program

Output

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Armstrong Number in C++ using Recursion

// Armstrong Number in C++ using Recursion
#include <bits/stdc++.h>
#include <cmath>
using namespace std;

// This function will check input number is Armstrong or not
// This will work recursively
int CheckArmstrong(int p) {
    if (p > 0)
        return (pow(p %10, 3) + CheckArmstrong(p / 10));
}

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

    cout << "-----Enter the integer number-----\n";
    cin >> x;

    // It will produce the final output

    if ((int) CheckArmstrong(x) == x)
        cout << x << " is an Armstrong number.\n";
    else
        cout << x << " is not an Armstrong number.\n";
    
    return 0;
}

Run Program

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C++ Program to Check Armstrong Number using While loop

// C++ Program to Check Armstrong Number using While loop
#include <iostream>
#include <cmath>
using namespace std;

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

    cout << "-----Enter the integer number-----\n";
    cin >> 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) {
        cout << x << " is an Armstrong number.\n";
    } else {
        cout << x << " is not an Armstrong number.\n";
    }
    return 0;
}

Run Program

Output

---

C++ Program to Check Armstrong Number without using pow() function

// C++ Program to Check Armstrong Number without using pow() function
#include <iostream>
using namespace std;

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
    // r - To store the result variable

    cout << "-----Enter the integer number-----\n";
    cin >> 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) {
        cout << x << " is an Armstrong number.\n";
    } else {
        cout << x << " is not an Armstrong number.\n";
    }
    return 0;
}

Run Program

Output

 

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