经典名题2----字典顺序列出集合的子集

/* ------------------------------------------------------ */
/* PROGRAM All Possible Subset by Lexical Order : */
/* This program generates all subsets by lexical order.*/
/* */
/* Copyright Ching-Kuang Shene July/05/1989 */
/* ------------------------------------------------------ */

#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! */
}
}