Key to CSE142 Midterm, Winter 2018

1.  Expression                                      Value
    ----------------------------------------------------------
    12 + 3 / 5 + 3 % 2                              13
    7 + 1 + "4 + 2" + 1 + 7                         "84 + 217"
    15 / 4 / 3.0 - 18 / 5 + (15 / 10.0)             -0.5
    !(7 * 2 != 42 && !(5 / 2 == 2))                 true
    6 % 4 + 4 % 6 + 6 % 6                           6


2. The program produces the following output:

        to be or ophelia to or
        not be or or to be
        or be or to to or
        to be or not to be?


3.      Method Call               Output Produced
        -----------------------------------------
        ifElseMystery(12, 45);    12 44
        ifElseMystery(5, 15);     8 5
        ifElseMystery(64, 8);     13 8
        ifElseMystery(12, 12);    1 11
        ifElseMystery(10, 3);     4 3
        ifElseMystery(120, 6);    122 6


4.      Method Call             Output Produced
        ---------------------------------------
        mystery(1);             1 1 
        mystery(4);             2 3
        mystery(6);             2 8


5.                x % 2 == 0               y > x               y % 2 == 1
            +---------------------+---------------------+---------------------+
    Point A | sometimes           | sometimes           | never               |
            +---------------------+---------------------+---------------------+
    Point B | sometimes           | always              | sometimes           |
            +---------------------+---------------------+---------------------+
    Point C | sometimes/always*   | always              | never               |
            +---------------------+---------------------+---------------------+
    Point D | sometimes/always*   | always              | never               |
            +---------------------+---------------------+---------------------+
    Point E | sometimes           | never               | sometimes           |
            +---------------------+---------------------+---------------------+

   * The correct answer is sometimes, but since students had not been introduced 
     to how % works with negative numbers, always was also accepted.


6. One possible solution appears below.

        public static int dogHears(String name, int numWords, Scanner console) {
            int count = 0;
          
            for (int i = 0; i < numWords; i++) {
                System.out.print("word? ");
                String input = console.next();

                System.out.print("dog hears: \"");
                if (input.equals(name)) {
                    System.out.print(name);
                    count++;
                } else {
                    System.out.print("blah");
                }
                System.out.println("\"");
            }
          
            return count;
        }
    

7. One possible solution appears below.

       public static void walkHome(int start, Random rand) {
          int distance = start;
          int total = 0;
          
          System.out.println("starting at " + start);

          while (distance > 0) {
             System.out.print("*");
             for (int i = 0; i < distance; i++) {
                System.out.print("-");
             }
             System.out.println("|^|");

             int steps = rand.nextInt(5) - 2;
             if (steps > distance) {
                steps = distance;
             }         
             distance -= steps;
             total += Math.abs(steps);
             System.out.println("moving " + steps + " step(s)");          
          }
          
          System.out.println("*|^|");
          System.out.println("made it home in " + total + " step(s)");
       }
    

8. Three possible solutions appear below.

        // get one digit, remove it, compare it to the new value of n % 10
        public static int digitsInARow(int n) {
            int max = 1;
            int count = 1;
            while (n > 0) {
                int next = n % 10;
                n = n / 10;
                if (n % 10 == next) {
                    count++;
                } else {
                    count = 1;
                }
                if (count > max) {
                    max = count;
                }
            }
            return max;
        }
        
        // keep track of a prev digit and compare it to the next digit
        public static int digitsInARow(int n) {
            int max = 1;
            int count = 0;
            int prev = -1;
            while (n != 0) {
                int next = n % 10;
                n = n / 10;
                if (next == prev) {
                    count++;
                } else {
                    count = 1;
                }
                max = Math.max(max, count);
                prev = next;
            }
            return max;
        }
        
        // count how many times the last 2 digits are divisible by 11
        public static int digitsInARow(int n) {
            int max = 1;
            int count = 1;
            while (n > 0) {
                if (n % 100 % 11 == 0) {
                    count++;
                } else {
                    count = 1;
                }
                max = Math.max(max, count);
                n = n / 10;
            }
            return max;
        }