knightstour.java

A demo for Knight s Tour problem by Java applet

import java.applet.Applet;
import java.awt.*;

public class KnightsTour extends Applet
{

    public void start()
    {
        MOUSE = false;
        cnt = 1;
        brd.resetBoard();
        x = 0;
        y = 7;
        knightx = (int)((double)dim * 0.10000000000000001D);
        knighty = dim * y + (int)((double)dim * 0.050000000000000003D);
        repaint();
    }

    public void compute()
    {
        brd.setCount(y, x, cnt++);
        brd.setKnightTrue(y, x);
        brd.computeValue();
        brd.computeBestMove(c);
        repaint();
    }

    public boolean mouseDown(Event evt, int x2, int y2)
    {
        if(x2 > dim * 8 || y2 > dim * 8)
            return false;
        if(!MOUSE)
        {
            x = x2 / dim;
            y = y2 / dim;
            if(x >= 8)
                x = 7;
            if(y >= 8)
                y = 7;
            knightx = dim * x + (int)((double)dim * 0.10000000000000001D);
            knighty = dim * y + (int)((double)dim * 0.050000000000000003D);
            if((y == 7 && x == 4 || y == 1 && x == 6 || y == 0 && x == 4) && cnt == 1)
                c = 0;
            compute();
        }
        MOUSE = true;
        return true;
    }

    public KnightsTour()
    {
        c = 1;
    }

    public void pressNext()
    {
        if(brd.getBestx(y, x) == -1)
        {
            return;
        } else
        {
            int tmp = x;
            x = brd.getBesty(y, tmp);
            y = brd.getBestx(y, tmp);
            knightx = dim * x + (int)((double)dim * 0.10000000000000001D);
            knighty = dim * y + (int)((double)dim * 0.050000000000000003D);
            compute();
            return;
        }
    }

    public boolean action(Event evt, Object obj)
    {
        if((evt.target instanceof Button) && MOUSE)
        {
            String buttonName = (String)obj;
            if(buttonName.equals("Next "))
                pressNext();
            else
            if(buttonName.equals("Solve"))
                while(cnt != 65) 
                    pressNext();
            else
            if(buttonName.equals("Reset"))
                start();
        }
        return true;
    }

    public void init()
    {
        resize(304, 365);
        Dimension d = size();
        setForeground(Color.cyan);
        setBackground(Color.white);
        setLayout(new BorderLayout());
        width = d.width;
        height = d.height;
        dim = width / 8;
        brd = new Board(width >= height ? height : width);
        x = 0;
        y = 7;
        Knight = getImage(getCodeBase(), "images/knight.gif");
        knightx = (int)((double)dim * 0.10000000000000001D);
        knighty = dim * y + (int)((double)dim * 0.050000000000000003D);
        next = new Button("Next ");
        solve = new Button("Solve");
        reset = new Button("Reset");
        Font font = new Font("Times", 1, 14);
        next.setForeground(Color.blue);
        next.setBackground(Color.white);
        solve.setForeground(Color.blue);
        solve.setBackground(Color.white);
        reset.setForeground(Color.blue);
        reset.setBackground(Color.white);
        Panel p = new Panel();
        p.add(next);
        p.add(solve);
        p.add(reset);
        add("South", p);
    }

    public void update(Graphics g)
    {
        paint(g);
    }

    public void paint(Graphics g)
    {
        brd.paint(g);
        if(Knight != null)
            g.drawImage(Knight, knightx - (int)((double)dim * 0.20000000000000001D), knighty - (int)((double)dim * 0.14999999999999999D), (int)((double)dim * 1.3D), (int)((double)dim * 1.2D), this);
    }

    private int width;
    private int height;
    private int dim;
    private Image Knight;
    private int knightx;
    private int knighty;
    private int x;
    private int y;
    private Board brd;
    private static int cnt = 1;
    private boolean MOUSE;
    private int c;
    private Button next;
    private Button solve;
    private Button reset;

}