CS 100: Section Assignment S8

Solutions

1.

public class ArrayOps
{	
    
	// Yields a reference to an array whose values are obtained by
	// performing a perfect shuffle of a. Assumes that a has even length.
	public static int[] Shuffle(int[] a)
	{
	   int n = a.length;
	   int m = n/2;
	   int[] b = new int[n];
	   for(int i=0;i&ltm;i++)
	   {
	      b[2*i]   = a[i];
	      b[2*i+1] = a[i+m];
	   }
	   return b;
	}
	
	// Perfect shuffles the entries in a. Assumes that a has even length.
	public static void ShuffleAlt(int[] a)
	{
	   int n = a.length;
	   int m = n/2;
	   int[] b = new int[n];
	   for(int i=0;i&ltm;i++)
	   {
	      b[2*i]   = a[i];
	      b[2*i+1] = a[i+m];
	   }
	   for(int i=0;i&ltn;i++)
	      a[i] = b[i];
	}
	
	// Prints on a single line the values in the (presumably short) array a.
	public static void println(int[] a)
	{
	   int n= a.length;
	   for(int k=0;k&ltn;k++)
	      Format.print(System.out," %2d",a[k]);
	   System.out.println(" ");
	}
	
	
	// Yields a reference to an array whose values are obtained by
	// performing a perfect 3-way shuffle of a. Assumes that a has multiple of 3 length.
	public static int[] shuffle3(int[] a)
	{
	   int n = a.length;
	   int m = n/3;
	   int[] b = new int[n];
	   for(int i=0;i&ltm;i++)
	   {
	      b[3*i]   = a[i];
	      b[3*i+1] = a[i+m];
	      b[3*i+2] = a[i+2*m];
	   }
	   return b;
	}
	
	// Yields the number of array entries that are strictly bigger than the average.
	public static int nBiggerThanAve(double[] a)
	{
	   double sum = 0;
	   for(int k=0;k&lta.length;k++)
	      sum = sum + a[k];
	   double ave = sum/a.length;
	   int count = 0;
	   for(int k=0;k&lta.length;k++)
	   {
	       if (a[k]>ave)
	          count++;
	   }
	   return count;
	}
	
	// Yields a reference to an array having the same length as a and whose
    // ith entry is a[(i+1)%a.length].
   public static int[] leftShift(int[] a)
   {
      int n = a.length;
      int[] b = new int[n];
      for(int i=0;i&ltn;i++)
         b[i] = a[(i+1)%n];
      return b;
   }

   // Yields a reference to an array having the same length as a and whose
   // ith entry is a[(i+k)%a.length]. Assume k is nonnegative.
   public static int[] leftShift(int[] a,int k)
   {
      int n = a.length;
      int[] b;
      b = leftShift(a);
      for (int j=1;j&ltk;j++)
      {
         b = leftShift(b);
      }
      return b;
   }
	
}

// S8A

import java.io.*;

public class S8A
{	
	public static void main(String args[])
	{
       TokenReader in = new TokenReader(System.in);
	    int kMax = 10000;
	    int D1, D2,score;
	    int[] n = {0,0,0,0,0,0,0,0,0,0,0,0,0};
	    for (int k=1;k<=kMax;k++)
	    {
	       D1 = (int)(1 + Math.floor(6*Math.random()));
	       D2 = (int)(1 + Math.floor(6*Math.random()));
	       n[D1+D2]++;
	    }
	    for (int i=2;i<=12;i++)
	       System.out.println("n[" + i + "] = " + n[i]);
	  
	  
	   in.waitUntilEnter();
	}

}

/* Output sample:

n[2] = 273
n[3] = 547
n[4] = 837
n[5] = 1103
n[6] = 1417
n[7] = 1674
n[8] = 1358
n[9] = 1143
n[10] = 821
n[11] = 548
n[12] = 279

*/

2.

import java.io.*;

public class S8B
{	
	public static void main(String args[])
	{
       TokenReader in = new TokenReader(System.in);
	   
	   int[] x={10,20,30,40,50,60,70,80,90,100,110,120};
	   int[] y = ArrayOps.shuffle3(x);
	   System.out.println("The 3-way shuffled array:");
	   for(int i=0;i&lt12;i++)
	      System.out.println("y[" + i + "] = " + y[i]);
		
	   in.waitUntilEnter();
	}

}
/* Output

The 3-way shuffled array:
y[0] = 10
y[1] = 50
y[2] = 90
y[3] = 20
y[4] = 60
y[5] = 100
y[6] = 30
y[7] = 70
y[8] = 110
y[9] = 40
y[10] = 80
y[11] = 120

*/

3.

import java.io.*;
public class S8C
{	
	public static void main(String args[])
	{
       TokenReader in = new TokenReader(System.in);
	    
	   double[] x = {3.1,-3.1,4.1,-4.1,5.2,-5.2,6.0,0.0};
	   int n = ArrayOps.nBiggerThanAve(x);
	   System.out.println("n = " + n);
	   in.waitUntilEnter();
	}

}

/* Output:

n = 4


*/

4.

import java.io.*;

public class S8D
{	
	public static void main(String args[])
	{
       TokenReader in = new TokenReader(System.in);
	   int[] x = {0,1,2,3,4,5,6};
	   int[] y;
	   y = x;
	   System.out.println(y[0] +" "+ y[1] +" "+ y[2]+" "+ y[3] +" "+ y[4] + " " + y[5] +" "+ y[6]);
	   y = ArrayOps.leftShift(x);
	   System.out.println(y[0] +" "+ y[1] +" "+ y[2]+" "+ y[3] +" "+ y[4] + " " + y[5] +" "+ y[6]);
	   y = ArrayOps.leftShift(x,3);
	   System.out.println(y[0] +" "+ y[1] +" "+ y[2]+" "+ y[3] +" "+ y[4] + " " + y[5] +" "+ y[6]);
	   in.waitUntilEnter();
	}

}
/* Output:

0 1 2 3 4 5 6
1 2 3 4 5 6 0
3 4 5 6 0 1 2

*/