Problem with modulus division

[GIjessiebear]

Can someone help me figure out how to use my modulus division for the thousands and hundreds within my code I think they're wrong.

#include <iostream>
using namespace std;
int main()
{
int num, ones, tens, hundreds, thousands;
int sum;
cout<<"enter an integer: ";
cin>>num;
while ((num<0)&&(num<=10000))
{
cout<<"enter an integer"<<endl;
cin>> num;
}
if (num >= 0 && num <= 9)
{
sum = num;
}
if (num >= 10 && num <= 99)
{
tens = ((num - (num%10)) / 10);
ones = (num - (tens * 10));
sum = tens + ones;
}
if (num >= 100 && num <= 999)
{
hundreds = ((num - (num%10)) / 100);
tens = ((num - (num%10)) / 10);
ones = (num - (tens * 10));
sum = hundreds + tens + ones;
}
if (num >= 1000 && num <= 9999)
{
thousands = ((num - (num%10)) / 1000);
hundreds = ((num - (num%10)) / 100);
tens = ((num - (num%10)) / 10);
ones = (num - (tens * 10));
sum = thousands + hundreds + tens + ones;
}
cout << "The sum of the digits is: " << sum << endl;
system("pause");
return(0);
}

[pogrady]

You have an extra parentheses here:

tens = (num - (num%10)) / 10);

[GIjessiebear]

If you have any insight into modulus division can you please tell me what I've done wrong for my hundreds and thousands.
if (num >= 100 && num <= 999)
{
hundreds = ((num - (num%10)) / 100);
tens = ((num - (num%10)) / 10);
ones = (num - (tens * 10));
sum = hundreds + tens + ones;
}
if (num >= 1000 && num <= 9999)
{
thousands = ((num - (num%10)) / 1000);
hundreds = ((num - (num%10)) / 100);
tens = ((num - (num%10)) / 10);
ones = (num - (tens * 10));
sum = thousands + hundreds + tens + ones;
}

[Chervil]

Using that general style of code, there isn't even a need for the modulus operator.

For example, a 3-digit value would work like this:

    if (num >= 100 && num <= 999)
    {
        hundreds = num / 100;
        tens = (num - hundreds*100) / 10;
        ones = num - hundreds*100 - tens*10;
        sum  = hundreds + tens + ones;
    }

But that's doing far too much work.
You could do the whole thing using a loop

    int sum=0;

    while (num > 0) {
        int digit = num%10;
        sum += digit;
        num/=10;
    }

    cout << "The sum of the digits is: " << sum << endl;

[GIjessiebear]

Thank you for the help I got my program to work properly two ways now. It's much appreciated help.

[Chervil]

Glad it was some help.

Actually, in the first version, there are separate cases and lots of "if" statements. You could probably just use the last version if (num >= 1000 && num <= 9999) even if the number has fewer than four digits it should still work. (Some values will of course be zero).

Similarly, the second version, rather than using a loop, could use the same concept, repeating the code several times. Then instead of storing each value in "digit", you could use separate fields for hundreds, tens etc.

There are always multiple ways to approach a problem, some may be more efficient than others, but even the other ways can be useful in understanding how the thing works.