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

public class GraphView extends JFrame implements MouseListener {

	private double edge[][];
	private double x[], y[];
	private int SIZE;
	private final int WIDTH = 450;  
	private final int HEIGHT = 450;
        private final int MARGIN = 200;
        
	public void update(Graphics g)	{
		paint(g); }
        
	public void makeLoop()
	{
		for(int i = 0; i < SIZE-1; i++)
		{
			edge[i][i+1] = 1;
			edge[i+1][i] = 1;
		}
		edge[0][SIZE-1] = 1;
		edge[SIZE-1][0] = 1;
		if (Math.random() > 0.5)
		{
			edge[0][SIZE/2] = 1;
			edge[SIZE/2][0] = 1;
		}
	}
	public void randomEdge() {
		for(int i = 0; i < SIZE; i++)
		{
			for(int j = 0; j < SIZE; j++)
				if (Math.random() < 1.0/SIZE)
				{
					edge[i][j] = 1;
					edge[j][i] = 1;
				}}
	}

        public GraphView()
	{
		addMouseListener(this);
                addWindowListener(new WindowAdapter(){
                public void windowClosing(WindowEvent we) { System.exit(0);} });
                
                setSize(HEIGHT+MARGIN,WIDTH+MARGIN);
  
		SIZE = 100;   // (int)(Math.random() * 123)+1;
		edge = new double[SIZE][SIZE];
		x = new double[SIZE];
		y = new double[SIZE];

                // create random locations for nodes
		for (int k = 0; k < SIZE; k++) {
			x[k] = Math.random();
			y[k] = Math.random();
		}

		if (Math.random() > 0.5)
			randomEdge();
		else
			makeLoop();
                show();
	}


	public void paint(Graphics g)
	{

		g.setColor(Color.white);
		g.fillRect(0,0,WIDTH+MARGIN, HEIGHT+MARGIN);
		g.setColor(Color.black);
		double maxX = x[0], maxY = y[0], minX = x[0], minY = y[0];
		for(int i = 0; i < SIZE; i++)	{
			if (x[i] > maxX)
				maxX = x[i];
			if (x[i] < minX)
				minX = x[i];
			if (y[i] > maxY)
				maxY = y[i];
			if (y[i] < minY)
				minY = y[i];	}
                
		for(int i = 0; i < SIZE; i++)	{
			int newX = (int)(WIDTH * (x[i] - minX))+(MARGIN/2);
			int newY = (int)(HEIGHT * (y[i] - minY))+(MARGIN/2);
			g.setColor(new Color(i*255/SIZE, 0, 255-i*255/SIZE));
			g.fillOval(newX, newY,20,20);
			for(int j = 0; j < SIZE; j++)
			{
                            if (edge[i][j] != 0)	{
				int newX2 = (int)(WIDTH*(x[j] - minX))+(MARGIN/2);
				int newY2 = (int)(HEIGHT*(y[j] - minY))+(MARGIN/2);
				g.drawLine(newX+10, newY+10, newX2+10, newY2+10);  }}
			g.setColor(Color.white);
			g.drawString(""+ (i+1), newX+3, newY + 15);  
	}}
                
	public void ChangeGraph() {
	int i, j;
		// add edge
		do {
			i = (int)(Math.random() * SIZE);
			j = (int)(Math.random() * SIZE);
		} while (i == j || edge[i][j] != 0);
		edge[i][j] = 1;
		edge[j][i] = 1;

		// remove edge
		while(true) {
			i = (int)(Math.random() * SIZE);
			j = (int)(Math.random() * SIZE);
			if (edge[i][j] != 0) {
				edge[i][j] = 0;
				edge[j][i] = 0;
				return;
			}
		}

	}
        
        public void addEdge(){
        int i, j;
		// add edge
		do {
			i = (int)(Math.random() * SIZE);
			j = (int)(Math.random() * SIZE);
		} while (i == j || edge[i][j] != 0);
		edge[i][j] = 1;
		edge[j][i] = 1;
        }
        
	public void mouseClicked(MouseEvent me)	{
            ChangeGraph();
            repaint();	}
        
	public void mouseExited(MouseEvent me) {}
	public void mouseEntered(MouseEvent me) { addEdge(); repaint();  }
	public void mouseReleased(MouseEvent me) {}
	public void mousePressed(MouseEvent me) {}
        
        public static void main(java.lang.String[] args) {
            new GraphView();
        }
        
}