[help]How to display the subsets

Question

I'd like to know how to display the subsets of the set that has
k elements.
For example,
if a set S={a,b,c},
then its subset is
{a},,{c},{a,b},{b,c},{a,c},{a,b,c},null}.
How do I code the above program in Java?
Any help??

Answer 1

public class Subsets {
  public static void main(String[] args) {
    int k = Integer.parseInt(args[0]);
    int sets = 1 << k;
    for (int i = 0; i < sets; i++) {
      if (i <= 0) {
        System.out.print("{null}");
      else {
        StringBuffer buf = new StringBuffer();
        int j = i; char c = 'a';
        while (j > 0) {
          if ((j & 1) > 0) buf.append(c);
          j >>= 1; c++;
        System.out.print("{" + buf + "}");
    System.out.println();
}