求解集合的子集

#include<stdio.h>
#include<string.h>
#define MAX_LENGTH 50
int number=0;

main()
{
void set(int,char *,char *);
char a[MAX_LENGTH],b[MAX_LENGTH]={"/0"};
int i=0;
printf("please input a string:");
scanf("%s",a);
set(i,a,b);
printf("the number of jihe:%d",number);
}
void set(int i,char *a,char *c){
char d[MAX_LENGTH];
strcpy(d,c);
if(i==strlen(a)){
printf("{%s}/n",c);
number++;
}
else{
set(i+1,a,d);
strncat(d,a+i,1);
set(i+1,a,d);
}
}

这里用一字符串来代表一个集合,比如输入CSDN,就表示集合{C,S,D,N}.求解它的子集并计算个数.输出结果如下:

please input a string:CSDN
{}
{N}
{D}
{DN}
{S}
{SN}
{SD}
{SDN}
{C}
{CN}
{CD}
{CDN}
{CS}
{CSN}
{CSD}
{CSDN}
the number of jihe:16