Help with a program

[frogfury]

Hey guys!

I just started out with C and thought the "Euler Project" problems would be a great way to practice.

However, I'm stuck at Problem 5 (What is the smallest number that is evenly divisible by all of the numbers from 1 to 20?). A quick google confirmed that my method was correct but I apparently made a logical error somewhere that gives me 0 as the output always. Any help will be appreciated.

long lcm(long a, long b);
long greater(long a, long b);
long lesser(long a, long b);

int main(void){

    long i;
	long m = 1;
 
    for ( i = 1; i <= 20; i++ )
    {
        m = lcm( m, i);
    }
    
    printf("%lf\n", m);
	system("PAUSE");
	return 0;
	 
}

long lcm(long a, long b)
{
    long larger_num;
    long smaller_num;
    long answer;
    long gcd;
    
    larger_num = greater(a, b);
    smaller_num = lesser(a, b);

    while ( smaller_num != 0 )
    {
        gcd = larger_num - smaller_num;
        larger_num = greater (gcd, smaller_num);
        smaller_num = lesser (gcd, smaller_num);        
    }

    answer = a * b / larger_num;
    return answer;    
}

long greater(long a, long b)
{
    if ( a > b)
    {
        return a;
    }
    else if ( b > a)
    {
        return b;
    }
    else
    {
        return a;
    }
}

long lesser(long a, long b)
{
    if ( a < b)
    {
        return a;
    }
    else if ( b < a)
    {
        return b;
    }
    else
    {
        return a;
    }
}

[Adak]

I would bet that %lf is the printf() format for a float - in fact, a double.

Use the right format for a long integer, of course.

[frogfury]

ahhh feel so dumb now.

Thanks a ton!

Edit: Still gives the wrong answer. Could anyone please point out the mistake I'm making?

[tabstop]

If you put the print inside the loop, you will see that your program thinks that the LCM of 232,792,560 and 20 is 18,044,195, which is odd. (That is to say: your multiplications overflow, so you should rearrange your calculations to do a division first.)

[frogfury]

Thank you!

This warrants another question: is there a better IDE than DEV-C++ with regards to debugging?

[Salem]

http://www.codeblocks.org/ is the new IDE on top of gcc/mingw (which you're already using).

[frogfury]

Thank you