/* Algorithm 4.1 in Ruskey's textbook: Next for subsets by counting. */

#include <stdio.h>
#include <stdlib.h>

#define MAX 20

enum BOOLEAN {FALSE, TRUE};
enum BOOLEAN done;

void PrintIt(int Array[], int n) {
  int i;
  
  for (i = 0; i < n; i ++) printf(" %d", Array[i]);

  printf("\n");
}

void Next(int Array[], int n) {
  int k = n-1;

  while (Array[k] == 1) {
    Array[k] = 0;
    k --;
  }

  if (k == -1) 
    done = TRUE;
  else
    Array[k] = 1;
}

int main(int argc, char *argv[]) {
  int n, i;
  int B[MAX+1];
  
  if (argc != 2) {
    printf("\n A single argument expected.\n");
    return 1;
  }

  n = atoi(argv[1]);

  if (n < 0) {
    printf("\n Positive number expected.\n");
    return 2;
  }

  if (n > MAX) {
    printf("\n The number cannot exceed %d.\n", MAX);
    return 3;
  }

  /*  Initialize  */

  for (i = 0; i < MAX+1; i ++) B[i] = 0;
  done = FALSE;

  /*  Main loop  */

  do {
    PrintIt(B+1,n);
    Next(B+1, n); }
  while (!done);
  
  return 0;
}