CSE 142 Final Key - Summer 2017

1. Reference Mystery

    2 [12, 8, 5]
    5 [2, 2, 5]
    16 3

2. Array Simulation

   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

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

4. Token-Based File Processing.  One possible solution appears below.

    public static void switchData(Scanner input) {
        String label = input.next();
        System.out.print(label);
        while (input.hasNextInt()) {
            int n1 = input.nextInt();
            if (input.hasNextInt()) {
                int n2 = input.nextInt();
                System.out.print(" " + n2);
            }
            System.out.print(" " + n1);
        }
        System.out.println();
    }


5. Line-Based File Processing.  One possible solution appears below.

    public static void formatList(Scanner input) {
        while (input.hasNextLine()) {
            String text = input.nextLine();
            if (!text.startsWith(".")) {
                System.out.println(text);
            } else {
                while (text.startsWith(".")) {
                    System.out.print("    ");
                    text = text.substring(1);
                }
                System.out.println("* " + text);
            }
        }
    }


6. Arrays.  One possible solution appears below.

    public static int minGap(int[] list) {
        if (list.length < 2)
            return 0;
        else {
            int min = list[1] - list[0];
            for (int i = 2; i < list.length; i++) {
                int gap = list[i] - list[i - 1];
                if (gap < min)
                    min = gap;
            }
            return min;
        }
    }

7. ArrayLists.  One possible solution appears below.

    public static void rearrange(ArrayList<Integer> list) {
        for (int i = 1; i <= list.size() / 2; i++) {
            int n = list.get(i);
            list.remove(i);
            list.add(n);
        }
    }

8. Critters.  One possible solution appears below.

    public class Eagle extends Critter {
        private int count;
        private int max;
    
        public Eagle() {
            count = 0;
            max = 1;
        }
    
        public Action getMove(CritterInfo info) {
            count++;
            if (count == 2 * max) {
                count = 0;
                max++;
            }
            if (info.getFront() == Neighbor.EMPTY) {
                return Action.HOP;
            } else if (info.getFront() == Neighbor.WALL) {
                return Action.RIGHT;
            } else {
                return Action.INFECT;
            }
        }
    
        public Color getColor() {
            if (count < max) {
                return Color.RED;
            } else {
                return Color.BLUE;
            }
        }
    
        public String toString() {
            return "<>";
        }
    }


9. Arrays.  One possible solution appears below.

    public static int[] reverseSublist(int[] list, int from, int to) {
        int[] result = new int[to - from];
        for (int i = 0; i < result.length; i++) {
            result[i] = list[to - i - 1];
        }
        return result;
    }

10. Programming.  One possible solution appears below.
        
    public static String encode(String s, int n) {
        String result = "";
        for (int j = 0; j < n; j++) {
            for (int i = 0; i < s.length() - j; i += n) {
                result += s.charAt(i + j);
            }
        }
        return result;
    }