List All Of The Subsets

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

My idea: one thinking of the algorithm backtracking is to generate a tree of subset and the condition of an element in the super set for a subset is either on or off.Hence we can specialize the subset tree to a binary tree and we print once when we reach the bottom of the tree each time.It is also easy to write a program.

 

#include <stdio.h>
 #define MAX 1000
 
 int n=3;  //the number of the set elements
 int set[MAX]={1,2,3};
 int count=0;//the number of the subset.
 
 void DFS(int level);
 void print_set();
 
 int main()
 {
     DFS(0);
     return 0;
 }
 
 void DFS(int level)
 {
     if(level==n)
     {
         print_set();
         return ;
     }
     int save=set[level];
     set[level]=0;
     int index=0;
     for(index=0;index<2;index++)
     {
         DFS(level+1);
         set[level]=save;
     }
 
 }
 
 void print_set()
 {
     int index;
     count++;
     printf("%d: {",count);
     for(index=0;index<n;index++)
     {
         if(set[index]!=0) 
             printf("%d ",set[index]);
     }
     printf("}\n");
 }