help with lists

Below is a program ive written to test if a number entered is a perfect number. However im having problems with making another function that will lists the perfect numbers from 1 to 1000. Any help or hints will be appreciated. Thanks

Code:

---

#include <stdio.h>

int factors( int );
int perfect( int );

int main()
{
        int number;

        printf("Enter Number: " );
        scanf( "%d", &number );

        printf( "%d\n", perfect( number ) );

        return 0;
}

int factors( number )
{
        int counter = 1, counter2 = 0, newNumber;

        while ( counter <= number ) {
                if ( ( number % counter == 0 ) && ( number != counter ) ) {
                        newNumber = counter;
                        counter2 += newNumber;
                }
                counter++;
        }

        return counter2;
}


int perfect( number )
{
        if ( number == factors( number ))
                return 1;
        else
                return 0;
}

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:confused:

Well you're going to have to use a loop. It will probably look something like this:

Code:

---


/* Headers and forward declarations */
#define MAX_NUM 1000

int main()
{
  int i;

  for( i = 0; i < MAX_NUM; ++i )
  {
    if( perfect( i ) )
    {
      printf( "%d\n", i );
    }
  }

  return 0;
}

---

I think something like that will probably do it. I think you should be able to tell what is going on in the loop as it is fairly straight-forward. If you need help understanding it let me know. Basically we will execute the commands within the for loop braces until the middle condition ( i < MAX_NUM ) is false.

Ive implemented what you have said and understand what is going on but i think im still missing something, you have declared int number, but it's not doing anything..
:confused:

Quote:

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Originally posted by kurz7
Ive implemented what you have said and understand what is going on but i think im still missing something, you have declared int number, but it's not doing anything..
:confused:

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Yeah you're right, I just copied and pasted your code for a starting point. You used number but I didn't. Take it out, you'll be fine. It should still work fine?

hmm not sure why its not working.
Just thinking about the code, will the counter always restart to 0 when the new number is called? Might keep incrementing so it will probably do 1 % 1, then 2 % 2 ...

i cuold be wrong

I didn't look at your perfect number algorithm at all. I was just showing you how to setup a for loop and use it. The loop index i should not be the problem. If you can't fix it by tomorrow let me know.

ive fixed the code to generate perfect numbers from 1 to 1000 but it still doesnt seem to be working.. not sure what the problem is, could be the counters.

Code:

---


#include <stdio.h>
#define MAX_NUM 1000

int factors( int );
int perfect( int );

int main()
{
  int i;

  for( i = 0; i < MAX_NUM; ++i )
  {
    if( perfect( i ) )
    {
      printf( "%d\n", i );
    }
  }

  return 0;
}

int factors( number )
{
        int counter = 1, counter2 = 0, newNumber;

        while ( counter <= number ) {
                if ( ( number % counter == 0 ) && ( number != counter ) ) {
                        newNumber = counter;
                        counter2 += newNumber;
                }
                counter++;
        }

        return counter2;
}


int perfect( number )
{
        if ( number == factors( number ))
                return 1;
        else
                return 0;
}

---

Program works fine for me. Start the loop counter at 1 instead of 0 because it reports 0 as a perfect number when in fact it is not. Again, program works for me.

hmm still doesnt seem to work, there should be 3 perfect numbers between 1 and 1000, did u get all 3? 6, 28, and another one ive forgotten..

it doesnt output anything

Output:
0
6
28
496

still doesnt work :(
is it a compiler problem? im on mandrake 8.2 and just using the gcc commands.

Quote:

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Originally posted by kurz7
still doesnt work :(
is it a compiler problem? im on mandrake 8.2 and just using the gcc commands.

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Put some extra printf() statements in there to help you debug it. Also, try fflush(stdout); at the end of the program (shouldn't be necessary but you never know ;) )