My C++ program keeps crashing

**Tech2011** · 12-02-2015

For a programming assignment, I have to ask the user for a number and determine if it is an abundant number or not and report that back to the user.

For some reason, when I enter a number to test this program, the program abruptly crashes after entering the number.

Code:

bool abundantTest(int n){					// boolean function to test if a number is abundant
	bool isAbundant = false;				// boolean flag to determine if the number is abundant
	int sum=0;

	for (int i = 0; i < n; i++){			// loop to check for the proper divisors of the number 'n'

		if (n % i == 0){
			sum = sum + i;
		}

	}

	if (sum > n){
		return true;
	}
	else{
		return false;
	}

}
int main(){
	int num;
	std::cout << "Enter a number to test if it is an abundant number: \n";
	cin >> num;
	abundantTest(num);
	if (abundantTest(num) == true){
		std::cout << "The number " << num << " is an abundant number.\n";
	}
	else if(abundantTest(num) == false){
		std::cout << "The number " << num << " is NOT an abundant number.\n";
	}
	else{

	}
	


}

I'm not sure why it is crashing. If anyone has any insight into this issue, your help would be greatly appreciated.

**laserlight** · 12-02-2015

On the very first iteration of the loop, you compute: n % 0, effectively trying to divide by 0.

By the way:

You don't make use of isAbundant
You call abundantTest up to three times when you only need to call it once.
abundantTest either returns true or false. There is no other possibility, so you have an else branch that will never be reached.

**Tech2011** · 12-02-2015

Oh! Haha! I should have caught that one! That's one of those "so stupid that I can't believe I didn't catch it" kind of errors. Thanks for noticing! And I also don't know why I had that third else branch in there. Thanks again!

**laserlight** · 12-02-2015

Originally Posted by Tech2011

And I also don't know why I had that third else branch in there.

As a matter of style, I would suggest:

Code:

int main() {
    std::cout << "Enter a number to test if it is an abundant number: \n";
    int num;
    if (cin >> num) {
        if (abundantTest(num)) {
            std::cout << "The number " << num << " is an abundant number.\n";
        }
        else {
            std::cout << "The number " << num << " is NOT an abundant number.\n";
        }
    }
    else {
        // report an input error to the user
        // ...
    }
}

**papagym177** · 12-03-2015

Don't you also have a error here where you use n instead of num? if (n % i == 0)

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