Check if a number is magic (Recursive sum of digits is 1) in C++

Here we will see one program, that can check whether a number is magic number or not. A number is said to be magic number, when the recursive sum of the digits is 1. Suppose a number is like 50311 = 5 + 0 + 3 + 1 + 1 = 10 = 1 + 0 = 1, this is magic number.

To check whether a number is magic or not, we have to add the digits until a single-digit number is reached.

Example

 Live Demo

#include <iostream>
using namespace std;
int isMagicNumber(int n) {
   int digit_sum = 0;
   while (n > 0 || digit_sum > 9) {
      if (n == 0) {
         n = digit_sum;
         digit_sum = 0;
      }
      digit_sum += n % 10;
      n /= 10;
   }
   return (digit_sum == 1);
}
int main() {
   int number = 50311;
   if(isMagicNumber(number)){
      cout << number << " is magic number";
   } else {
      cout << number << " is not magic number";
   }
}

Output

50311 is magic number

Arnab Chakraborty

Updated on 21-Oct-2019 08:46:25

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