GCD Algo. Help

dontcare · 10-16-2004, 12:10 PM

I need help using the GCD Algo. in my program, I can't figure out to use the algo in my program. The algo:

Code:

 int gcd(int a, int b){
 assert(b != 0);
 int rem = a % b;
 while(rem !=0 ){
 a = b;
 b = rem;
 rem = a % b;
 }
 return b;
 
 The program:
 #include <iostream>
 using namespace std;
 
 
 int Num, Num2, Denom, Denom2;
 int res_up, res_down;
 int Low_Value, High_Value;
 char opchar,answer,symbol;
 
 
 void Calculate()
 {
 switch (opchar) {
 	case '+':
 		res_up=(Denom2*Num) + (Denom*Num2);
 			res_down= Denom*Denom2;
 				symbol = '+';
					 break;
 	case '-':
 		res_up=(Denom2*Num) - (Denom*Num2);
			 res_down= Denom*Denom2;
 				symbol = '-';
					 break;
	case '*':
 		res_up= Num * Num2;
 			res_down= Denom * Denom2;
 				symbol = '*';
 					break;
 	case '/':
 		res_up= Num * Denom2;
 			res_down= Denom * Num2;
 				symbol = '/';
					 break;
 
 	default: // If operator is illegal shut program down
 		cout << "Invalid operator." << endl;
 	}
 }
 
 void input()
 
 {
 cout << "Enter an operation to perform { + - / * } ";
 cin >> opchar;
 cout << endl;
 cout << "Enter the numerator and denominator for the first fraction; include a space: ";
 cin >> Num >> Denom;
 cout << endl;
 cout << "Enter the numerator and denominator for the second fraction; include a space: ";
 cin >> Num2 >> Denom2;
 cout << endl;
 
 }
 
 
 //-------------------------------------------------------------------
 
 
 void output()
 
 {
 cout << "\n " << Num << " " << Num2 << " " << res_up << " " << endl;
 cout << "--- " << symbol << " --- = --- =\n";
 cout << " " << Denom << " " << Denom2 << " " << res_down << endl;
 cout <<"Would you like to do another fraction? ";
 cin >> answer;
 cout << endl;
 
 }
 
 int main()
 {
 do{
  input(); 
  Calculate();
  output();
 } while ((answer == 'y') || (answer == 'Y')); 

 return 0; 

 }

jordanGSU · 10-16-2004, 07:20 PM

The Greatest Common Denominator should return an integer which is the GCD of the two numbers passed into the function. I didnt run your code to see if it works, but the GCD fucnction looks correct, in case its not, here is a version of it that I wrote a while back

// returns the greatest common divisor of A and B
long GCD(long A, long B)
{ if( B==0 ) return A;
return GCD(B,A%B);
}

I cant really tell what the rest of your code is doing...hope this helps a little.

FYI: global variables are bad programming practice unless they are absolutely necessary. Youve got like 11...makes my head want to explode

dontcare · 10-16-2004, 09:50 PM

Thanks for the advice, the problem i had earlier was solved.