CS 209 – Java Programming – Assignment #22

Chapter 18:  Recursion - Hand in this work (Turn in word processor output for the exercises - include program listings and sample output):  Exercise #s 1, 2, and 3 below– Total points:  60

Hint: The recursive method printArrayHelper() in the Print class here could serve as a model for solving problems 18.2 and 18.3.

// Print.java - program prints an array using recursion

public class Print
{
   public static void printArray(int[] array)
   {      // call helper function to do work
      printArrayHelper(array, 0);
      System.out.println(); // add ending newline
   } // end method printArray

   private static void printArrayHelper(int[] array, int k)
   {     // recursively print array
      if (k == array.length)
         return;
      System.out.print(array[k] + " ");
      printArrayHelper(array, k + 1);
   } // end method printArrayHelper

   public static void main(String args[])
   {
      int array[] = { 8, 22, 88, 34, 84, 21, 94 };
      System.out.print("Array is: ");
      printArray(array);	// print array recursively
   } // end main
} // end class Print


(10) 18.1. Show the return value of method mystery() and the output of this program.












(25) 18.2. Write and test a recursive method strRev() that takes a character array containing a string as an argument and prints the string backward.

Hint: User String method toCharArray(), which takes no arguments, to get a char array containing the elements of the String.

/* Sample output:
 * Enter a string: sooner or later one of us must know
 * wonk tsum su fo eno retal ro renoos
 * Enter a string: Hannah
 * hannaH
 */


(25) 18.3. Write and test a recursive method minRecurs() that returns the smallest element in an int array.

     /* Output:
 * 22 88 8 94 78 84 96 73 34
 * Smallest value in the array: 8
 */