Chapter 5, Problem 20C

Recursive method to rearrange an array of integers:

Create the method rearrange() that accepts the input parameter as “a”, “start”, and “end” to rearrange the array integers that all even numbers appears before the odd numbers.

//Define the rearrange() method

public static int[] rearrange(int[] a, int start, int end)

{

  //Check whether "start" is equal to "end"

  if (start==end)

  //Return the array value

  return a;

/*Otherwise, check and rearrange odd number after the even number. */

  else

  {

  //Loop executes until length of array value

  for(int i=start; i<=end; i++)

  {

/*Check whether mod of array value by "2" is not equal to "0". */

  if(a[i]%2!=0)

  {

/*Call the swap() method to rearrange the array values. */

  swap(a, i, end);

  //Display the rearranged array values

  System.out.println(Arrays.toString(a));

/*Recursively call rearrange() method by passing the parameters of "a", "i", and "end-1" and then return it */

  return rearrange(a,i,end-1);

  }

  }

  }

/*Recursively call rearrange() method by passing the parameters of "a", "end", and "end" and then return it */

  return rearrange(a,end,end);

}

Create the method swap() that accepts the input parameter as “a”, “a1”, and “a2” to swap the array integers.

//Define the swap() method

private static void swap(int[] a, int a1, int a2)

{

/*Declare the temporary variable to hold the array value...