List All Of The Subset In Another Method

Problem description:Please list all of the subsets of a known set including the empty set.

Thinking: the subset's sum of a super set is (n is the number of the super set element) while a n-bit binary space could express  numbers too.So our target is to generate all of the binary numbers in n bit space.Before solving the problem,please look at this point:

11111 01111
+                 1
-------------------
11111 10000

When the number add 1,the current bit will become to 0 and generate a carry if it was 1.Next,the previous bit 1 will become 0 with a carry,too.If its current bit is 0 ,it becomes 1 without a carry and stop the addition.Hence,the program process is clear.

#include <stdio.h>
#include <math.h>
#define MAX 1000

int n=4;// the number of the set elements
int set[MAX]={1,2,3,4};
int path[MAX]={0};
int count=1;

//prototype
void print_set();

int main()
{
    int sum=(int)pow(2.0,n)-1;
    int index,index_re;
    printf("%d:{}\n",count);
    for(index=0;index<sum;index++)
    {
        for(index_re=n-1;index_re>=0;index_re--) 
        {
            if(path[index_re]==1) 
                path[index_re]=0;
            else
            {
                path[index_re]=1;
                break;
            }
        }
        count++;
        printf("%d:{",count);
        print_set();
    }
    return 0;
}

void print_set()
{
    int index;
    for(index=0;index<n;index++)
    {
        if(path[index]!=0) 
            printf("%d ",set[index]);
    }
    printf("}\n");
}

Reference material: C语言名题精选百则技巧篇 in Chinese.