Recursive and Non-Recursive powersets?

[csisdifficult]

Hello all,

I need some help creating codes to make a powerset...

Here is the skeleton:

public static StringList powerRecursive (String s) {



}

public static StringList powerLooping (String s) {



}

Thanks!

[ozzyman]

If S is the set {x, y, z}, then the subsets of S are:

{} (also denoted , the empty set)
{x}
{y}
{z}
{x, y}
{x, z}
{y, z}
{x, y, z}


Is this what you are trying to do?

[csisdifficult]

Basically, but all in one string:

["", a, b, ab, ba, abab, baba]

[csisdifficult]

Please? Someone help?

[ozzyman]

In one List, of course.

Something to start you off:

//define a List because you don't know how many items you need to store in it
List<String> powerSet = new ArrayList<>();

//define set to make powerSet from
char[] aSet = new char[] {'a', 'b', 'c'};

//loop through each character
    //define a String to store full set
    String fullSet = "";
    //add blank to List
    powerSet.add(fullSet);
for (int i=0; i<aSet.length; i++) {
    //add each item in set
    powerSet.add(aSet[i]);
    //compile the full set
    fullSet += aSet[i];
}
    //add full set
    powerSet.add(fullSet);

So far this would get us everything except the 'ab', 'ac' and 'bc'.

ab, ac, bc... is like this: aa, ab, ac, ba, bb, bc, ca, cb, cc
but with same letter combos removed (aa, bb, cc)
and doubles removed (ab = ba, ac = ca, bc = cb)

[csisdifficult]

That sort of helps, I think I got it. Thanks!