Most frequently asked interview question #9 with solution

Given an integer number n, return the difference between the product of its digits and the sum of its digits.
Example:
n = 234
output = 15 which is ((2*3*4) - (2+3+4))

Solution in C++:

    int subtractProductAndSum(int n) {
            int sum = 0;
            int prd = 0;
            int tmp = 0;
            bool is_first = true;
        while(n != 0){

            tmp = n % 10;
            n   = n / 10;
            sum += tmp;

            if(is_first){
                is_first = false;
                prd = tmp;
            } else {
                 prd *= tmp;
            }
        }

        return prd - sum;
    }