armstrong_number.cpp

// C++ program to determine whether the number is Armstrong number or not 

/* A positive integer of n digits is called an Armstrong number of order n (order is number of digits)
if: abcd... = pow(a,n) + pow(b,n) + pow(c,n) + pow(d,n) + .... */

#include<bits/stdc++.h> 
using namespace std; 

/* Function to calculate x raised to the power y */
int power(int x, unsigned int y) { 
	if( y == 0) 
		return 1; 
	if (y%2 == 0) 
		return power(x, y/2)*power(x, y/2); 
	return x*power(x, y/2)*power(x, y/2); 
} 

/* Function to calculate order of the number */
int order(int x) { 
	int n = 0; 
	while (x) 
	{ 
		n++; 
		x = x/10; 
	} 
	return n; 
} 

/* Function to check whether the given number is Armstrong number or not */
bool isArmstrong(int x) { 
	// Calling order function 
	int n = order(x); 
	int temp = x, sum = 0; 
	while (temp) { 
		int r = temp%10; 
		sum += power(r, n); 
		temp = temp/10; 
	} 

	// If satisfies Armstrong condition 
	return (sum == x); 
} 

// Driver Program 
int main() { 
	int x = 153; 
	cout << isArmstrong(x) << endl; 
	x = 1253; 
	cout << isArmstrong(x) << endl; 
	return 0; 
}