//PowersetApp.java
//power set  in "binary number order"


import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;


public class PowersetApp extends JApplet {

    JTextField inputNField;
    int N;
    JLabel errorLabel;
    JTextArea listArea;
    Set powerset;
    TreeSet alphaPowerset;
    JRadioButton radioAlphaButton, radioSizeButton, radioBinaryButton;
    ButtonGroup buttonGroup;


    public void init() {
	Container container = getContentPane();
	int panelRowsSize = 2;
	container.setLayout( new GridLayout( 1, panelRowsSize) );

	JPanel [] panelRows = new JPanel[panelRowsSize];

	//left side panel
	panelRows[0] = new JPanel();
	container.add( panelRows[0] );
	panelRows[0].setLayout( new GridLayout( 2, 1 ) );

	JPanel topleftPanel = new JPanel();
	panelRows[0].add( topleftPanel );

	JPanel bottomleftPanel = new JPanel();
	panelRows[0].add( bottomleftPanel );
	bottomleftPanel.setLayout( new GridLayout( 3, 1 ) );

	//right side panel
	panelRows[1] = new JPanel();
	panelRows[1].setLayout( new FlowLayout() );
	container.add( panelRows[1] );


	powerset = new LinkedHashSet();  //for insertion order

	Font bigFont = new Font( "Monospaced", Font.BOLD, 16 );
	TextFieldHandler handleTextField = new TextFieldHandler();

	JLabel inputNLabel = new JLabel( "set size" );
	inputNLabel.setFont( bigFont );
	topleftPanel.add( inputNLabel );

	inputNField = new JTextField( 3 );
	inputNField.setFont( bigFont );
	topleftPanel.add( inputNField );
	inputNField.addActionListener( handleTextField );


	errorLabel = new JLabel( "" );
	errorLabel.setFont( bigFont );
	topleftPanel.add( errorLabel );    

	radioAlphaButton = new JRadioButton( "Alphabetic order" );
	bottomleftPanel.add( radioAlphaButton );
	RadioButtonHandler radioButtonHandler = new RadioButtonHandler();
	radioAlphaButton.addItemListener( radioButtonHandler ); 

	radioSizeButton = new JRadioButton( "By size order" );
	bottomleftPanel.add( radioSizeButton );
	radioSizeButton.addItemListener( radioButtonHandler ); 

	radioBinaryButton = new JRadioButton( "By binary order" );
	bottomleftPanel.add( radioBinaryButton );
	radioBinaryButton.addItemListener( radioButtonHandler ); 

	buttonGroup = new ButtonGroup();
	buttonGroup.add(radioAlphaButton);
	buttonGroup.add(radioSizeButton);
	buttonGroup.add(radioBinaryButton);


	listArea = new JTextArea( 20, 30 );
        Font smallFont = new Font( "Monospaced", Font.BOLD, 12 );
        listArea.setFont( smallFont );
        JScrollPane listScroll = new JScrollPane( listArea );
        panelRows[1].add( listScroll );
                                                                           
    }


    public void start() {
	inputNField.requestFocusInWindow();
	radioBinaryButton.setSelected( true ); 
    }


    private class TextFieldHandler implements ActionListener {
        public void actionPerformed( ActionEvent event ) {

	    errorLabel.setText( "" );

	    int n=0;
	    try {
		n = Integer.parseInt( inputNField.getText() );
	    }
	    catch (NumberFormatException e) {
		errorLabel.setText( "integer please" );
		return;
	    }
	    if ( n <= 0 ) {
		errorLabel.setText( "positive integer please" );
		return;
	    }

	    if ( n > 31 ) {
		errorLabel.setText( "<32 please" );
		return;
	    }

	    N = n;  //field N

	    listArea.setText( "" );		    

	    char[] A="abcdefghijklmnopqrstuvwxyzABCDEF".toCharArray(); 
	    
	    int two_n = 1 << n;

	    powerset.clear();

	    //generate in binary number order	
	    for (int i=0; i<=two_n-1; i++) {
		String subset = "";

		for (int j=0; j<n; j++)

		    if (((i>>j) & 1) == 1)
			subset += "" + A[j];

		powerset.add( subset );

                if ( radioAlphaButton.isSelected() )
		    alphaSort();
		else if ( radioBinaryButton.isSelected() )
		    listArea.append( subset + "\n" );
                else if ( radioSizeButton.isSelected() )
		    sizeSort();
		
	    }
	}
    }

    private void alphaSort() {
	listArea.setText( "" );
	alphaPowerset = new TreeSet( powerset );
	Iterator it = alphaPowerset.iterator();
	while ( it.hasNext() ) {
	    listArea.append( (String)it.next() );
	    listArea.append( "\n" );
	}
    }
    

    private void sizeSort() {
	listArea.setText( "" );
	String s;
	for (int size=0; size<=N; size++) {
	    TreeSet sizePowerset = new TreeSet();
	    Iterator it = powerset.iterator();
	    //build set of length 'size'
	    //System.out.println(""+size);
	    while ( it.hasNext() ) {
		s = (String)it.next();
		if ( s.length() == size )
		    sizePowerset.add( s );
	    }
	    //iterate over the sorted set of length 'size' strings
	    Iterator it2 = sizePowerset.iterator();
	    while ( it2.hasNext() ) {
		listArea.append( (String)it2.next() );
		listArea.append( "\n" );
	    }
	}
    }

    private class RadioButtonHandler implements ItemListener {
        public void itemStateChanged( ItemEvent event ) {
	    
	    listArea.setText( "" );
	    
            if ( event.getSource() == radioAlphaButton ) {
                if ( radioAlphaButton.isSelected() )
		    alphaSort();
	    }
            else if ( event.getSource() == radioSizeButton ) {
                if ( radioSizeButton.isSelected() )    
		    sizeSort();
            }
            else if ( event.getSource() == radioBinaryButton ) {
                if ( radioBinaryButton.isSelected() ) {
		    Iterator it = powerset.iterator();
		    while ( it.hasNext() ) {
			listArea.append( (String)it.next() );
			listArea.append( "\n" );
		    }
		}
            }
        }
    }
}