armstrong.c

/*
     An Armstrong number is a number that is equal to the sum of digits raise to the power total number of digits in the number.
     Some Armstrong numbers: 153, 370, 1634
 */
#include <stdio.h>
#define LL long long

int countDigits(int n) {

	int count = 0;

    while(n) {

    	count++;

    	n/= 10;
    }

    return count;
};

LL pow2(int a, int b) {

   int i, p = 1;

   for(i = 1; i <= b; ++i) {

   	   p = p * a;        
   }

   return p;
};


int isArmstrong(int n) {

    int sum = 0, 

        count = countDigits(n), n2 = n;

        while(n) {

        	sum += pow2(n%10, count);

        	n/=10;
        }

        if(sum == n2) {

                 while(n2) {

                 	 printf("%d ^ %d + ", n2 % 10, count);

                 	 n2 /= 10;
                 }

        	     return 1;
        }        	     

            else 

            	      return 0;
      
};

int main() {

	int n;

    printf("%s", "N=");
	scanf("%d", &n);

    if(isArmstrong(n)) {

       printf("\nThe number is Armstrong.\n");

    } else {

       printf("\nThe number is not Armstrong.\n");    	
    }
	return(0);
}