C Program to Display Armstrong Number Between Two Intervals

In this example, you will learn to find all Armstrong numbers between two integers entered by the user.

A positive integer is called an Armstrong number (of order n) if

abcd... = an + bn + cn + dn + â€‹

In the case of an Armstrong number of 3 digits, the sum of cubes of each digit is equal to the number itself.

For example, 153 is an Armstrong number because

153 = 1*1*1 + 5*5*5 + 3*3*3â€‹

Armstrong Numbers Between Two Integers :

Program :

#include 
#include 
int main() {
  int low, high, number, originalNumber, rem, count = 0;
  double result = 0.0;
  printf("Enter two numbers(intervals): ");
  scanf("%d %d", &low, &high);
  printf("Armstrong numbers between %d and %d are: ", low, high);

  // swap numbers if high < low
  if (high < low) {
    high += low;
    low = high - low;
    high -= low;
  }
   
  // iterate number from (low + 1) to (high - 1)
  // In each iteration, check if number is Armstrong
  for (number = low + 1; number < high; ++number) {
    originalNumber = number;

    // number of digits calculation
    while (originalNumber != 0) {
      originalNumber /= 10;
      ++count;
    }

    originalNumber = number;

    // result contains sum of nth power of individual digits
    while (originalNumber != 0) {
      rem = originalNumber % 10;
      result += pow(rem, count);
      originalNumber /= 10;
    }

    // check if number is equal to the sum of nth power of individual digits
    if ((int)result == number) {
      printf("%d ", number);
    }

    // resetting the values
    count = 0;
    result = 0;
  }

  return 0;
}

Output :

Enter two numbers(intervals): 150
3000
Armstrong numbers between 150 and 3000 are: 153 370 371 407 1634