import java.util.ArrayList;
import java.util.List;

/**
 * Created by igalshilman on 01/10/2016.
 */
public class IntSets
{
    public static void main(String[] args)
    {
        long a = empty();
        a = add(a, 1);
        a = add(a, 2);
        a = add(a, 10);
        a = add(a, 30);

        System.out.println("a: " + elements(a));

        long b = set(1, 30, 50); // shorter way defining a set
        System.out.println("b: " + elements(b));

        long b_a = difference(b, a);
        System.out.println("b - a  = " + elements(b_a));

        long b_or_a = union(b, a);
        System.out.println("b U a = " + elements(b_or_a));

        long b_and_a = intersect(b, a);
        System.out.println("b AND a = " + elements(b_and_a));

        System.out.println();
        System.out.println("powerset of [0,1,2]:");
        System.out.println();

        for (long set : powerset(3))
        {
            System.out.println(elements(set));
        }

    }

    public static long empty()
    {
        return 0;
    }

    public static long add(long set, int element)
    {
        return set | (1L << element);
    }

    public static long set(int... elements)
    {
        long s = empty();
        for (int element : elements)
        {
            s = add(s, element);
        }
        return s;
    }

    public static List<Integer> elements(long set)
    {
        List<Integer> elements = new ArrayList<Integer>();
        int element = 0;
        while (set > 0)
        {
            if ((set & 1) == 1) // if the right most bit is 1
            {
                elements.add(element);
            }
            element++;
            set = set >> 1; // move all the bits one position to the right.
        }
        return elements;
    }

    public static long intersect(long a, long b)
    {
        return a & b;
    }

    public static long union(long a, long b)
    {
        return a | b;
    }

    public static long difference(long a, long b)
    {
        return a & ~b;
    }

    public static List<Long> powerset(long n)
    {
        List<Long> powerSet = new ArrayList<Long>();
        for (long i = 0; i < Math.pow(2, n); i++)
        {
            powerSet.add(i);
        }
        return powerSet;
    }
}