C++ Program to Check Armstrong Number using user-defined function

An integer number is called Armstrong number if sum of the cubes of its digits is equal to the number itself. For example, 371 is an Armstrong number since 3*3*3 + 7*7*7 + 1*1*1 = 371.

Lets write a program to check whether the input number is armstrong number using user-defined function. If you are looking for a program to check armstrong number using loop then see: C++ Program to check Armstrong number using for loop.

Example: Check whether input number is Armstrong Number or not

To understand this program you should have the knowledge of if-else statement, while loop and user-defined function.

#include <iostream>
using namespace std;
bool checkArmstrongNumber(int num);

int main(){
   int num;
   bool flag;
   cout<<"Enter a positive  integer: ";
   cin>>num;

   //Calling function
   flag = checkArmstrongNumber(num);
   if(flag == true)
      cout<<num<<" is an Armstrong number.";
   else
      cout<<num<<" is not an Armstrong number.";

   return 0;
}
/* User defined function that checks whether the passed
 * integer number is Armstrong or not
 */
bool checkArmstrongNumber(int num) {
   int temp, sum=0, digit;
   bool isArm;

   temp = num;
   while(temp != 0) {
      digit = temp % 10;
      sum = sum +(digit * digit * digit);
      temp = temp/10;
   }
   if (sum==num)
      isArm = true;
   else
      isArm = false;

   return isArm;
}

Output:

Enter a positive  integer: 371
371 is an Armstrong number.