Check if a large number is divisibility by 15 in C++

Here we will see how to check a number is divisible by 15 or not. In this case the number is very large number. So we put the number as string.

To check whether a number is divisible by 15, if the number is divisible by 5, and divisible by 3. So to check divisibility by 5, we have to see the last number is 0 or 5. To check divisibility by 3, we will see the sum of digits are divisible by 3 or not.

Example

#include <bits/stdc++.h>
using namespace std;
bool isDiv15(string num){
   int n = num.length();
   if(num[n - 1] != '5' && num[n - 1] != '0')
      return false;
      long sum = accumulate(begin(num), end(num), 0) - '0' * n;
   if(sum % 3 == 0)
      return true;
      return false;
}
int main() {
   string num = "154484585745184258458158245285260";
   if(isDiv15(num)){
      cout << "Divisible";
   } else {
      cout << "Not Divisible";
   }
}

Output

Divisible