C++ program to check Armstrong number

In this chapter of C++ program tutorial out task is: 

• Write a c++ program to check whether a number is armstrong number or not

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C++ program to check Armstrong number

Given below is the c++ program to check armstrong number or not.

/*  Program Name : To check whether a number is Armstrong or not
    Program Author : Sayantan Bose
*/
#include<iostream>

//math.h header file is used for the sqrt function
#include <math.h>

using namespace std;

//This function will return the sum of the digits powered to the length of the inputed number.
int arms (int num)
{
    int r,sum=0,num1=num,c=0;
    
while(num!=0)
    {
        c++;
        num=num/10;
     }

while(num1!=0)
     {
        r=num1%10;
        num1=num1/10;
        sum=sum+pow(r,c);
     }

    return sum;
}  

// This is the main function

int main() {

int num,sum=0,new_num;
 
   cout<<"Enter any number to check Armstrong:";
   cin>>num;
   new_num=num;
   sum=arms(num);

    if(sum==new_num)
        cout<<sum<<" is an Armstrong number";
    else
        cout<<sum<<" is not an Armstrong number";

	return 0;
}

OUTPUT

Enter the number to check Armstrong:

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EXPLANATION :

In the above c++ program to check if a number is Armstrong or not:

• A number is said to be Armstrong if and only if the sum of its digits powered to the length of the number is equal to the number itself.
• For example: 153 is an Armstrong number. Because 153 can be written as the sum of 1³+5³+3³, where 3 is the length of the provided number 153.
• In the method arms, we are calculating the sum of each digit powered to the length of the inputed number. And then the sum is returned to the main method.
• In the main method the sum is then compared with the original number provided as input.
• If both of them turn out to be equal the number is an Armstrong number else it isn't.

​You can see the above code execution and output in codeblocks IDE: