Any hint would be appreciated......

[auntdeen]

My son & I are throughly frustrated....we've gotten this far on a program for the perfect numbers between 1 - 100, but have hit many dead ends. So far, the output is "3206" - but in the many attempts have had outputs of 0, 1, blank, and a list of 100 zeros with a 2 at the end. I know that it's something simple, but sometimes the more you mess with something, the harder it is to spot the obvious mistake. If someone would be kind enough to point me in the right direction, so that I can point my kid in the right direction, I would truly appreciate it!

 /*This program displays all the perfect numbers in the range of 1-100 */


#include<stdio.h>
#include<math.h>
#include"genlib.h"
#include"simpio.h"



 int perfect(int num);

 main()

	{
		int num, p;

		printf ("the perfect numbers in the range of 1 - 100 are:\n\n");

		for (num=2; num<=100; num+=2);  /*all known perfect numbers below the
													value of 10 to the 300th power are
													even*/


			p =  perfect (num);
			printf ("%d\n", p);

  }

  int perfect(int num)

		{

		int i, sum, p;



			for (i=2; i<num; i++)

				{

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

					if (sum == num)
							{
							sum = p;
							}




			}


				return (p);

		}

[Mister C]

Try removing the semicolon after the for loop

for (num=2; num<=100; num+=2);

[auntdeen]

Thank you....

Still generates "3206", sigh.......

[quzah]

When using multiple lines of code in a loop, you must use braces. Example:

for (num=2; num<=100; num+=2)
{
	p =  perfect (num);
	printf ("%d\n", p);
}

Otherwise what happens is this:

for (num=2; num<=100; num+=2)
{
	p =  perfect (num);
}
printf ("%d\n", p);

See the difference?

Quzah.

[auntdeen]

Banging my head against the wall.......

Yes, I see, LARGE sigh. I wish that I had the right mindset for this, and I wish that I had tackled this at a much younger age. I hate making stupid mistakes like that!

I think that I have been too focused on the bottom function, trying to figure out why it's generating the funky numbers (now it's a 3206 and 99 "8729"s)... obviously we have something very wrong with the simple mathematics there

Thank you so much for your help!

[Hammer]

Look in the perfect() function at the variable p. Lets follow this through quickly:

- You create it with
>int p;
- The next thing you use p for is this:
>sum = p;
This is a problem because you haven't yet assigned a value to p, so how can you assign p's value to sum?

[C-learning]

Shouldn you try sum == num
after the loop.
ANd if im not that wrong you never get a perfect number because
you start with 2.
1 is the divisor of all numbers and you never add 1 to sum.
And it enough to loop to num / 2 because n/(n/2+1) is smaller than two and the number it self is not considered with perfect numbers