CSCI A201/A597 Lecture Notes 28 Spring 2000

FOUR: THROWING DARTS

Here's the basic program:

import element.*;

public class Darts {
    public static void main(String[] args) {
	Circle c = new Circle(100, 100, 100); 
	int hits = 0; 
	int attempts = 10000; 
	for (int i = 0; i < attempts; i++) {
	    int x = (int) (Math.random() * 200); 
	    int y = (int) (Math.random() * 200); 
	    Pt m = new Pt(x, y); 
	    if (c.contains(m)) {
		hits = hits + 1; 
	    } 
	}

	System.out.println("Throwing " + attempts + 
                           " darts makes PI seem like: " + 
                           4.0 * hits / attempts); 
    }
} 

import element.*;
import java.awt.Color; 

public class GraphDarts {
    public static void main(String[] args) {
	DrawingWindow d = new DrawingWindow(); 
	Circle c = new Circle(100, 100, 100); 
	d.draw(c); 
	int hits = 0; 
	int misses = 0; 
	int attempts = Integer.parseInt(args[0]); 

	for (int i = 0; i < attempts; i++) {
	    int x = (int)(Math.random() * 200); 
	    int y = (int)(Math.random() * 200); 
	    Pt m = new Pt(x, y); 
	    if (c.contains(m)) {
		d.setForeground(Color.blue); 
		hits = hits + 1; 
	    } else {
		misses = misses + 1; 
		d.setForeground(Color.red); 
	    } 
	    d.draw(m);
	}
	System.out.println("Throwing " + attempts + 
                           " darts makes PI seem like: " + 
                           4.0 * hits / attempts); 

	System.out.println("Experiment PI. Attempts: " + attempts); 
	System.out.println("   Hits: " + hits); 
	System.out.println("   Misses: " + misses);
	System.out.println("   Check attempts: " + (hits + misses)); 
	System.out.println("End of experiment"); 
    }
} 

Here's a program developed by Ben Hui.

import element.*;
import java.util.Random;

public class Ben {
    public static void main(String [] args){
	Random gen = new Random ();
        int size = Integer.parseInt(args [0]);
        int numbers [] = new int [size];
        for (int i = 0; i < numbers.length; i++)
	    numbers[i] = Library.Random (0,200,gen);
        for ( int i = 0; i

ONE: SORTING RANDOM ARRAYS

Here's the basic part of it, without the drawing window interface.

import element.*;
import java.util.Random;

public class DNM{
  public static void main(String [] args){
      int size = Integer.parseInt(args [0]);
      int[] alpha = Library.createArray(size); 
      Library.show(alpha); 
      Library.sort(alpha); 
      Library.show(alpha); 
  }
}

class Library{
    public static int Random(int low, int high, Random gen){
	int x = Math.abs(gen.nextInt())%(high-low+1);
        x = x + low;
        return (x);
    }
    public static void show(int[] numbers) { 
      for (int i = 0; i < numbers.length; i++)
	  System.out.print(numbers [i] +" ");
          System.out.println();    
    }
    public static void sort(int[] numbers) { 
      for (int i = 0 ; i <= numbers.length-1; i++)
	  for (int j = 0; j < numbers.length; j++){
	      if (numbers[i]<numbers[j]){
                  int temp;
                  temp = numbers[j];
                  numbers[j] = numbers[i];
                  numbers[i] = temp;
	      }
          }
    }
    public static int[] createArray(int size) {
      Random gen = new Random();
      int numbers [] = new int [size];
      for (int i = 0; i <numbers.length; i++)
	  numbers [i] = Library.Random(0,200,gen);
      return numbers; 
    }

}

SIXTEEN: CHECKERBOARD

Here's a solution developed with Peter James.

import element.*;

public class CB {
    public static void main(String[] args) {
	DrawingWindow d = new DrawingWindow(); 
	Rect[][] g = new Rect[8][8]; 
	int xL = 10, yL = 10, w = 10, h = 10; 
	for (int i = 0; i < g.length; i++) {
	    for (int j = 0; j < g[i].length; j++) {
		g[i][j] = new Rect(xL + j * w, yL + i * h, w, h); 
		if ((i + j) % 2 == 0) {
		    d.fill(g[i][j]); 
		} else {
		    d.draw(g[i][j]);
		} 
	    } 
	}
	while (true) {
	    Pt m = d.awaitMouseClick(); 
	    for (int i = 0; i < g.length; i++) {
		for (int j = 0; j < g[i].length; j++) {
		    if (g[i][j].contains(m)) {
			System.out.println(i + ", " + j); 
		    } 
		}
	    }
	}
    }
}