Armstrong Number in C++

  • November 23, 2022
  • C++
palindrome string

What is Armstrong Number?

The Armstrong number is a number that is equal to the sum of its digits’ cubes. Armstrong numbers include 0, 1, 153, 370, 371, and 407.

Let’s look at why 371 is amrstrong in nature:

371 = (3*3*3)+(7*7*7)+(1*1*1)    
where:    
(3*3*3)=27    
(7*7*7)=343    
(1*1*1)=1    
So:    
27+343+1=371    

Approach: The approach is to first count the number of digits (or find the order). Let n be the number of digits. Calculate r^n for each digit r in the input number x. If the sum of all such values equals the number, return true; otherwise, return false.

Program code:

#include <iostream>
using namespace std;

int main() {
		int n ;
		cin>>n;
		int temp = n;
		int p = 0;

		/*function to calculate
		the sum of individual digits
		*/
		while (n > 0) {

			int rem = n % 10;
			p = (p) + (rem * rem * rem);
			n = n / 10;
		}

		/* condition to check whether
		the value of P equals
		to user input or not. */
		if (temp == p) {
			cout<<temp<<"  is an Armstrong No.";
		}
		else {
			cout<<temp<<" is not an Armstrong No.";
		}
	return 0;
}


Output:

321
321 is not an Armstrong No.

153
153 is an Armstrong No.

Note: also read about Factorial of a given Number

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