Thread: Factorising problem

I am writing a simple prgram to show that factors of an integer input

I'm not sure if i'm going about writing this the right way, I get an output, but I need to somehow restrict the display to only show the integer results instead of all the results i have written the following:

Code:

#include <stdio.h>

int main (void) {

int input;
int a;
int k;

printf("Enter number to be factorised:\n");
scanf("%d", &input);

printf("the factors of %d are\n", input);

for (k=1; k<=input; k++) {

a = input/k;

printf("%d\n", a);

}

    return 0;
}

But the output of this is not what i want, say if i enter 7, t gives me

Code:

the factors of 7 are
7
3
2
1
1
1
1

but what i want it to show is, say if i enter 1001

Code:

the factors of 1001 are
1001
143
91
77
13
11
7
1

any suggestions?

If you want to check that k is a factor of input, check that it divides into input with no remainder.

use something like

Code:

if (input%k==0)

do not use

Code:

a = input/k;

Also, try thinking of ways to optimize your algorithm

Hmm.... my C coding probably blows, but here is what went through my snoodle.

Code:

#include <stdio.h>
#include <stdlib.h>

#define BUFF 30

int main (void) {

    int input, value, upper, k;
    static int array[BUFF];
    int i = 0;

    printf("Enter number to be factorised:\n");

    /*doesn't handle alphanumberic chars at the end of number*/
    if(scanf("%d", &input) != 1)
	exit(1);

    printf("the factors of %d are\n", input);

    for (k=1 ; k<=input; k++) {
	value = input %k;
	if (value == 0) {
	    array[i] = k;
	    i++;
	}
    }
    
    upper = i-1;

    for(;((upper>=0) && upper<BUFF);upper--) {
	printf("%d\n", array[upper]);
    }
   
    return 0;
}

$gcc -g -Wall factor.c -o factor
$./factor
Enter number to be factorised:
7
the factors of 7 are
7
1
$./factor
Enter number to be factorised:
1001
the factors of 1001 are
1001
143
91
77
13
11
7
1
$./factor
Enter number to be factorised:
8
the factors of 8 are
8
4
2
1
$./factor
Enter number to be factorised:
b
$./factor
Enter number to be factorised:
b100
$./factor
Enter number to be factorised:
adadade3
$


Ohh..... my aching hips.

Hmmm..... I wasn't aware you could do that. You win. Pull my finger.

Code:

#include <stdio.h>

int main (void)
{
	int n;
	int i;

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

	if (n <= 1) {
		printf("Bad input.\n");
		return 1;
	}
	for (i = 2; n != 1; i++) {
		while (n % i == 0) {
			printf("%d ", i);
			n /= i;
		}
	}

	return 0;
}

27 = 3 3 3
50 = 2 5 5
5642 = 2 7 13 31