列出所有子集（字典顺序）

#include <stdio.h>

#include <stdlib.h>

#define MAXSIZE 20

#define LOOP 1

void main(void)

{

int set[MAXSIZE];

int n, i;

int position;

char line[100];

printf("\nAll Possible Subsets Generation by Lexical Order");

printf("\n================================================");

printf("\n\nNumber of Elements in the Set --> ");

gets(line);

n = atoi(line);

printf("\n{}"); /* the empty set */

position = 0; /* start from the 1st pos. */

set[position] = 1; /* it gets a '1' */

while (LOOP) { /* loop until done... */

printf("\n{%d", set[0]); /* print one result */

for (i = 1; i <= position; i++)

printf(",%d", set[i]);

printf("}");

if (set[position] < n) { /* this pos. can be inc*/

set[position+1] = set[position] + 1; /* YES*/

position++; /* inc. next pos. */

}

else if (position != 0) /* NO, the 1st pos? */

set[--position]++; /* backup and increase */

else /* NO, the 1st pos and can */

break; /* not be inc. JOB DONE! */

}

}