UNIVERSITY OF TORONTO
	Faculty of Arts and Science
	DECEMBER EXAMINATIONS 1998
	CSC 108F

SAMPLE ANSWERS
--------------
These answers are the ones I used for my lecture section. Some of them
are necessarily the same for all sections, but others may vary somewhat
on account of different instructors' views on programming style.

	-- J. Clarke

1. [10 marks = 2 + 2 + 6]

(a)

Delete "this", and make print() "static".

(b)

Change "private" to "public" in line 2.

(c)


i) yes

			yes		no

ii) Delete this line:
      Philosopher x = new Philosopher ("Jacques"); 

iii) (2)

2. [20 marks]

// Write the rest of the main( ) method here.
---------------------------------------------
      while (!word.equals (STOPPER)) {
         if (word.equals (PARAGRAPH))
            builder.newLie();
         else
            builder.addWord(word);
         word = text.nextWord();
      }
      builder.newLine();
   } // end main()
} // end class TextFormatter

// Write the rest of LineBuilder here.
--------------------------------------
class LineBuilder {
   private int lineLength;
   private String line; // This is an addition.

   public void addWord (String newWord) {
      if (line.length() + 1 + newWord.length() > lineLength)
         newLine();
      if (line.length() != 0)
         line += " ";
      line += newWord;
   }

   public LineBuilder (int length) {
      lineLength = length;
      line = "";
   }

   public void newLine() {
      if (line.length() == 0) 	// If PARAGRAPH or STOPPER or word of
         return; 		// length = lineLength comes right after
				// a call to newLine(), do nothing.
      System.out.println(line);
      line = "";
   }
}

3. [10 marks]

// (beginning of program omitted)
int [][] A = new int [...]; // details of A's instantiation omitted

// Here we put values in A. That part is omitted too.
...

final int rows = A.length;
final int cols = A[0].length; // Assume rows > 0.
int[][] tran = new int[cols][rows];

for (int i = 0; i < rows; i++)
   for (int j = 0; j < cols; j++)
      tran[j][i] = A[i][j];

4. [20 marks]

import java.util.*;
import java.io.*;

public class Q4 {

    public static void main(String args[]) throws IOException {
	BufferedReader in = new BufferedReader (new InputStreamReader (System.in), 1);
	final String STOPPER = "QQQ";
	
	// a table of line lengths we've seen
	Vector table = new Vector();
	
	// Read the input.
	while (true) {
	    String line = in.readLine();
	    if (line.equals(STOPPER)) break;
	    LengthRecord item = lookUp (table, line.length());
	    if (item != null)
		item.count++;
	    else {
		item = new LengthRecord();
		item.length = line.length();
		item.count = 1;
		table.addElement (item);
	    }
	}
	
	// Print the table contents.
	for (int i = 0; i < table.size(); i++) {
	    LengthRecord item = (LengthRecord) table.elementAt(i);
	    System.out.println ("length " + item.length + " occurrences " + item.count);
	}   

    }
    
    // lookUp: retrieve the record for a given length from a table
    // If no such record found, return null.
    private static LengthRecord lookUp (Vector table, int length) {
	for (int i = 0; i < table.size(); i++) {
	    LengthRecord element = (LengthRecord) table.elementAt(i);
	    if (element.length == length)
		return element;
	}
	
	return null;
    }

}

class LengthRecord {
    public int length;
    public int count;
}

5. [20 marks]

public static double sqrt (double a) {
   if (a<0)
      throw new SqrtException(); // OK to omit definition of SqrtException

   double x = a/2;
   double xBetter = (x + a/x)/2;
   while (Math.abs(x - xBetter) > 0.00001*Math.abs(xBetter)) {
      x = xBetter;
      xBetter = (x + a/x)/2;
   }
   return xBetter;
}