Chapter 5, Problem 15C

Recursive method to display all subsets of set of “n” elements:

Let us take the input for subset is {1, 2, 3} and this method displays the subsets of {}, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}.

Method definition:

Create the method subsetAll() that accepts the input parameter of ArrayList as “set” to compute the output all the subsets of set of “n” elements without repeating any subsets by calling this method recursively.

//Define the subSetAll() method

private static ArrayList<ArrayList<Integer>> subsetAll(ArrayList<Integer> set)

{

  //Create an object for ArrayList

ArrayList<ArrayList<Integer>> s = new ArrayList<ArrayList<Integer>>();

  //Check whether size of "set" is equal to "0"

if (set.size() == 0)

{

  //Add the ArrayList

s.add(new ArrayList<Integer>());

}

/*Otherwise, call the subSetALL() method recursively to display all subset of set of "n" elements. */

  else

  {

  //Create an object for ArrayList

  ArrayList<Integer> rSet = new ArrayList<Integer>();

  //Add all the elements in the "set"

  rSet.addAll(set);

/*Remove the element from "rSet" and assign into "first" variable. */

  int first = rSet.remove(0);

/*Call the subSetALL() method recursively to display all subset of set of "n" elements and result is assigned to ArrayList object "subsets"*/

ArrayList<ArrayList<Integer>> subsets = subsetAll(rSet);

  //Add all the elements in the "subsets"

  s...