/* Algorithm 4.2 in Ruskey's textbook: Recursive procedure to generate subsets in lexicographic order. */

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

#define MAX 20

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

  printf("\n");
}

void Subsets(int Array[], int n, int pos) {
  if (pos > n-1) PrintIt(Array, n);
  else {
    Array[pos] = 0;
    Subsets(Array, n, pos+1);
    Array[pos] = 1;
    Subsets(Array, n, pos+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; i ++) B[i] = 0; */

  Subsets(B, n, 0);
  
  return 0;
}