CS 100: Lecture L8

February 18

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public class upNdown
{
   // Yields the number of turns required to reach 
   // unity when the up-and-down sequence begins 
   // at nStart.
   public static int turns(int nStart)
   {
      int n = nStart;
      int k = 0;
      while(n>1)
      {
         if(n%2==0)
            {n = n/2;}
         else
            {n = 3*n+1;}
         k++;
      }
      return k;       
   } 
}

// Plot upNdown.turns


import java.io.*;
import java.awt.*;

public class CUCSDrawing extends Frame
{
    final int L = 50;      // Horizontal coordinate of plot window's left edge.
    final int T = 50;      // Vertical coordinate of plot window's top edge.
    final int W = 800;     // The width of the plot window.
    final int H = 500;     // The height of the plot window.
    final double Y = 200;  // The y-value associated with the top of the plot window.
    final double S = H/Y;  // Pixels per unit y-value.
    final int BASE = T+H;  // Vertical coordinate of the plot windows bottom edge.
    
	public void paint(Graphics g)
	{
	   // Draw a black plot window.
	   g.fillRect(L,T,W,H);
	   
	   // Draw the upNdown "histogram"
	   g.setColor(Color.magenta);
	   int y; 
	   for(int x=1;x<=W;x++)
	   {
	      // Assign to y the number of turns required for starting value x.
	      y = upNdown.turns(x);
	      // Depict this value with a properly scaled vertical line segment.
	      g.drawLine(L+x,BASE,L+x,(int)(BASE-y*S));
	   }
	   
	   // Draw 3 equally spaced horizontal gridlines.
	   g.setColor(Color.cyan);
	   for(int v=BASE-H/4;v>T;v=v-H/4)
	      {g.drawLine(L,v,L+W,v);}
	
	}
	
}

public class L8
{
	public static void main(String args[])
	{
		CUCSDrawing d = new CUCSDrawing();
		d.resize(1000,600);                   
		d.move(0,75);
		d.setTitle("Up 'N Down");                 
		d.show();
		d.toFront();
	}
}