Divisibility by 12 for a Large Number in C++

In this tutorial, we are going to write a program that checks whether the given large number in string format is divisible by 12 or not.

We are going to use a little bit of math to solve this problem. If the number is divisible by 3 and 4, then the number will divisible by 12.

A number is divisible by 3 if the sum of its digits is divisible by 3.

A number is divisible by 4 if the last two digits of the number are divisible by 4.

We are going to utilize the above statements and complete the program.

Example

Let's see the code.

 Live Demo

#include <bits/stdc++.h>
using namespace std;
bool isNumberDivisibleBy12(string num) {
   if (num.length() >= 3) {
      int last_digit = (int)num[num.length() - 1];
      if (last_digit % 2 != 0) {
         return 0;
      }
      int second_last_digit = (int)num[num.length() - 2];
      int sum = 0;
      for (int i = 0; i < num.length(); i++) {
         sum += num[i];
      }
      return (sum % 3 == 0 && (second_last_digit * 10 + last_digit) % 4 == 0);
   }
   else {
      int number_as_int = stoi(num);
      return number_as_int % 12 == 0;
   }
}
int main() {
   string num = "1212121212121212121212121212";
   if (isNumberDivisibleBy12(num)) {
      cout << "Yes" << endl;
   }
   else {
      cout << "No" << endl;
   }
   return 0;
}

Output

If you execute the above program, then you will get the following result.

Yes

Conclusion

If you have any queries in the tutorial, mention them in the comment section.