Divide throw 3

Question

Hello,

i need to write a programm which reads in a three digit number, then gets the sum of it (2+3+4), and will check if it is dividable by 3.

Input: 234
sum= 9
Output= The number is dividable by 3 with a remainder of 0.

#include<iostream>
#include<cmath>

using namespace std;

int main ()
{
bool run {true};
while (run)
{
long num, counter;
double sum {0};
cout<< "Type in three numbers ";
cin>> num;

if (num>=1000)
cout<< "Choosen number has more then three digits!!! will calculate anyway\n";

// hab es nicht hinbekommen das das programm hier dann nochmals von vorne beginnt

while (num!=0)
{
counter=num%10;
sum+=counter;
num=num/10;
}

cout<< "\n" <<"The sum of the three digits is "<< sum <<"\n\n";
cout<< sum << "Can the sum of digits be divided by 3? " ;

// if (sum % 3)
// {
// cout<< "yes with a remainder of " << (sum%=3) ;
// }

char answer;
cout<< "Run the Programm again? (y/n): ";
cin>> answer;
run = answer == 'y';
}
return 0;
}

Answer 1

Sorry, but I think I missed the part where you explained the problem?

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Answer 2

Yippiekayo Romeo
The modulo operator % only works with integral types. Your <sum> variable is a double type (floating point type) and that's the cause of the problem.

if (sum % 3)
// attempt to use binary modulo operator on floating point type (<sum> is a double)

You have two choices here, either change the <sum> variable type to an integral type that fits the purpose (short, int, long, long long or their unsigned versions), or alternatively, use `fmod` function which supports modulo operation on floating point types.

Reference:

http://www.cplusplus.com/reference/cmath/fmod/

Hth, cmiiw

Answer 3

Perfect thank you.
about the code, it feels like i dont used the if, while statements correct. Or the order itself isnt that good, any feedback?

Answer 4

Sorry, I didn't get what you mean.

You have two `if` statements there, one for checking input greater or equal to 1000, and another one for checking remainder of <sum> divided by 3. Which one you mean?

Answer 5

I mean the structure of the whole code, what can I do better. I know which statements I got in my own code