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

public class SierpinskiDriver extends JApplet{
  int level = 0;

  public void init(){
    String levelStr = JOptionPane.showInputDialog("Enter the depth of recursion: ");

    level = Integer.parseInt(levelStr);
  }//end of init()

  private Point midPoint(Point pOne, Point pTwo){
    Point mid = new Point((pOne.x + pTwo.x) / 2, (pOne.y + pTwo.y) / 2);
    return mid;
  }//end of method.

  public void paint(Graphics g){
    Point pointOne = new Point(20, 280);
    Point pointTwo = new Point(280, 280);
    Point pointThree = new Point(150, 20);

    drawSierpinski(g, level, pointOne, pointTwo, pointThree);
  }//end of method

  private void drawSierpinski(Graphics g, int lev, Point p1, Point p2, Point p3){
    Point midP1P2;
    Point midP2P3;
    Point midP3P1;

    if(lev > 0){
      g.drawLine(p1.x, p1.y, p2.x, p2.y);
      g.drawLine(p2.x, p2.y, p3.x, p3.y);
      g.drawLine(p3.x, p3.y, p1.x, p1.y);

      midP1P2 = midPoint(p1, p2);
      midP2P3 = midPoint(p2, p3);
      midP3P1 = midPoint(p3, p1);

      drawSierpinski(g, lev - 1, p1, midP1P2, midP3P1);
      drawSierpinski(g, lev - 1, p2, midP2P3, midP1P2);
      drawSierpinski(g, lev - 1, p3, midP3P1, midP2P3);

    }//end of IF
  }//end of method.
}