Self-Review Questions

1. Consider the following mystery method:

   public static void mystery(int level)
   {
      if (level == 0)
      {
         System.out.print("*");
      }
      else
      {
         System.out.print("[");
   
         mystery(level - 1);
   
         System.out.print(",");
   
         mystery(level - 1);
   
         System.out.print("]");
      }
   

   Show the output that would be produced by the following calls

   • mystery(1);

   • mystery(2);

2. Examine the following code segment

   public class Demo
   {
      public static void main(String[] ags)
      {
         System.out.println( fun(5) );
      }
   
      public static int fun(int n)
      {
         if (n == 0)
            return 1;
         else
            return n + fun(n/2);
      }
   }
   

   and predict the output

   • A)   5
   • B)   7
   • C)   8
   • D)   9

3. Write a recursive method that prints the following pattern?

   #####
   ####
   ###
   ##
   #
   

4. Write a recursive method that prints the following pattern?

   #
   ##
   ###
   ####
   #####
   

5. Write a recursive method that removes all nodes with data equal to keyItem

   public void removeAll(Object keyItem, Node current)

6. Write a recursive method that removes all nodes with data greater than keyItem

   public void removeAllGreaterItems(Comparable keyItem, Node current)

7. Write a recursive method (you are allowed to have helper-methods)

   public void pattern(int[] input)

   that takes an array of integers input and prints it out input.length times. The print must be in the following specific order: each line starts at a new element and wraps around to the beginning of the array (if needed) until each element has been printed out.

   This sample output occurs when the input is the array {0, 1, 2, 3, 4}:

   0 1 2 3 4
   1 2 3 4 0
   2 3 4 0 1
   3 4 0 1 2
   4 0 1 2 3