Re: Subsets from a set


stdazi@xxxxxxxxx wrote:
Hello,

I was just playing with some coding problem, when I figured out I'll
need to retrieve all the subsets from a given set. As I'm not very good
at solving that kind of algorithms, the code produced would get too
dirty and slow, that's why I'm wondering if someone can provide me a
simple algorithm procedure or code snippet. The code I'm playing with
is made in C and uses arrays to emulate sets.

This is the best i could code :

#include <stdio.h>
#include <math.h>

static void subsets(int *s,size_t nel) {
unsigned i,v,c;
for (i=0;i<pow(2,nel);i++) {
putchar('{');
for (v=i,c=0;v;v>>=1,c++)
if (v&1)
printf(" %d " ,s[c]);
printf("}\n");
}
}
int main() {
int ourset[5]={1,2,3,4,5};
subsets(ourset,5);
return 0;
}

It's quite fast, the only thing that can be improved is the byte
checking loop which (now) checks every bit.

.

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