practice-final-answers.md

Practice Final Answers

Week 10

1. Reference Mystery (5 points)

   11 [21] 30,41
   10 [21] 30,41
   11 [23] 31,42
   10 [23] 31,42
   

2. Array Simulation (10 points)

   Original List	Final List
   {2, 5, 8}	{2, 5, 10}
   {3, 4, 7, 5}	{3, 4, 10, 5}
   {2, 4, 6, 2, 6}	{2, 4, 8, 2, 14}
   {4, 5, 8, 9, 3}	{4, 5, 12, 9, 15}
   {1, 2, 8, 5, 10, 5, 4}	{1, 2, 9, 5, 19, 5, 23}

3. Inheritance (6 points)

   a			c			a			c
   a 1			c 1			a 1			d 1
   b 2			c 2			c 2			c 2
   

4. Token-Based Processing (10 points)

   One possible answer shown below.

   public static void printStrings(Scanner pairs) {
   	while(pairs.hasNext()) {
   		int times = pairs.nextInt();
   		String phrase = pairs.next();
   
   		for(int i = 0; i < times; i++) {
   			System.out.print(phrase);
   		}
   		System.out.println();
   	}
   }

5. Line-Based File Processing (9 points)

   One possible answer is shown below.

   public static int analyzeParagraphs(Scanner input) {
   	int max = 0;
   	int lineCount = 0;
   
   	while (input.hasNextLine()) {
   		String line = input.nextLine();
   		if (!line.equals("")) {
   			lineCount++;
   		}
   
   		if (line.equals("") || !input.hasNextLine()) {
   			System.out.printf("%d-line paragraph\n", lineCount);
   			max = Math.max(max, lineCount);
   			lineCount = 0;
   		} 
   	}
   
   	return max;
   }

6. Arrays (10 points)

   One possible answer is shown below.

   public static void minToFront(int[] list) {
   	if (list.length != 0) {
   		int minIndex = 0;
   		for (int i = 1; i < list.length; i++) {
   			if (list[i] < list[minIndex]) {
   				minIndex = i;
   			}
   		}
   
   		int temp = list[0];
   		list[0] = list[minIndex];
   		list[minIndex] = temp;
   	}
   }

7. ArrayList (10 points)

   One possible answer is shown below.

   public static void reverse3(ArrayList<Integer> list) {
   	for (int i = 0; i < list.size() - 2; i+=3) {
   		int temp = list.get(i);
   		list.set(i, list.get(i + 2));
   		list.set(i + 2, temp);
   	}
   }

8. Critters (15 points)

   One possible answer is shown below.

   public class Raccoon extends Critter {
   	private Random r;
   	private String appearance;
   	private Color c;
   
   	public Raccoon() {
   		r = new Random();
   		appearance = "<->";
   		c = Color.BLUE;
   	}
   
   	public Color getColor() {
   		return c;
   	}
   
   	public Action getMove(CritterInfo info) {
   		toggleColor();
   		if (info.getFront() == Neighbor.OTHER) {
   			appearance = "<I>";
   			return Action.INFECT;
   		} else if(r.nextInt(2) == 0) {
   			appearance = "<R>";
   			return Action.RIGHT;
   		} else {
   			appearance = "<L>";
   			return Action.LEFT;
   		}
   	}
   
   	public String toString() {
   		return appearance;
   	}
   
   	private void toggleColor() {
   		if (c == Color.RED) {
   			c = Color.BLUE;
   		} else {
   			c = Color.RED;
   		}
   	}
   }

9. Arrays (15 points)

   One possible answer is shown below.

   public static int[] collapse(int[] list) {      
   	int[] output = new int[(list.length + 1) / 2];
   
   	for (int i = 0; i < list.length; i++) {
   		output[i / 2] += list[i];
   	}
   	  
   	return output;
   }

10. Programming (10 points)

    One possible answer is shown below.

    public static void printReversed(String phrase) {
    	for (int i = 0; i < phrase.length(); i++) {
    		if (phrase.charAt(i) == ' ') {
    			System.out.print(" ");
    		} else {
    			String reverse = "";
    			while (i < phrase.length() && phrase.charAt(i) != ' ') {
    				reverse = phrase.charAt(i) + reverse;
    				i++;
    			}
    			i--;
    			System.out.print(reverse);
    		}
    	}
    	System.out.println();
    }