Question

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

Write a C function to print all Armstrong numbers between a given interval. Then write a C program to keep reading two integers and print all Armstrong numbers between these two integers by calling that function.

Answer 1

Program code to copy:-

#include <stdio.h>
#include <math.h>

/* Function prototype */
void printArmstrong(int start, int end);

int main()
{
   /* Declaration of variables two store two integers*/
   int num1, num2;
  
   /*Prompt & read starting integer number of interval*/
   printf("Enter the starting number of interval: ");
   scanf("%d", &num1);
  
   /*Prompt & read ending integer number of interval*/
   printf("\nEnter the ending number of interval: ");
   scanf("%d", &num2);
  
   /*Calling function to print armstrong number in a given interval
   by passing two integer number*/
   printArmstrong(num1, num2);
  
   return 0;
}

/*Definition of function to print armstrong number in a given interval.
This function receives two integer parameters which represents the interval*/
void printArmstrong(int start, int end)
{
   int i, n, sum, digit;
  
   printf("\nThe Armstrong numbers between %d and %d:\n", start, end);
  
   /*The outer loop will exeuted within given inteval of numbers*/
   for(i=start; i<=end; i++)
   {
       /*Initilize sum with 0 for every number to be checked for armstrong*/
       sum = 0;
       /*Making another copy of number to be checked for armstrong*/
       n = i;
          
       /*Inner loop will calculate sum of the cubes of digits of number*/  
       while(n!=0)
       {
           /*Extracting last digit from number*/
           digit = n % 10;
           /*Adding sum of the cube of digit*/
           sum = sum + pow(digit, 3);
           /*Removing last digit from number*/
           n = n / 10;
       }
       /*Checking & printing the armstrong number*/
       if(i==sum)
           printf("%d ", i);
   }
}

Screenshot of output:-