/**
* Copyright (C) 2001-2017 by RapidMiner and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapidminer.com
*
* This program is free software: you can redistribute it and/or modify it under the terms of the
* GNU Affero General Public License as published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
* even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License along with this program.
* If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.operator.learner.associations;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
/**
* The power set of a collection of items.
*
* @author Sebastian Land
*
* @param <ItemT>
* the item type
*/
public class PowerSet<ItemT> implements Iterable<Collection<ItemT>>, Iterator<Collection<ItemT>> {
private ArrayList<ItemT> set;
private boolean[] subSetIndicator;
public PowerSet(Collection<ItemT> collection) {
set = new ArrayList<ItemT>(collection);
}
@Override
public Iterator<Collection<ItemT>> iterator() {
return new PowerSet<ItemT>(set);
}
public Collection<ItemT> getComplement(Collection<ItemT> collection) {
Collection<ItemT> complement = new ArrayList<ItemT>(set.size() - collection.size());
Iterator<ItemT> iterator = set.iterator();
for (ItemT item : collection) {
while (iterator.hasNext()) {
ItemT currentSetItem = iterator.next();
if (currentSetItem == item) {
break;
} else {
complement.add(currentSetItem);
}
}
}
while (iterator.hasNext()) {
complement.add(iterator.next());
}
return complement;
}
@Override
public boolean hasNext() {
if (subSetIndicator == null) {
return true;
} else {
for (int i = 0; i < subSetIndicator.length; i++) {
if (!subSetIndicator[i]) {
return true;
}
}
return false;
}
}
@Override
public Collection<ItemT> next() {
// do initialising
if (subSetIndicator == null) {
subSetIndicator = new boolean[set.size()];
} else {
// increase binary counter
for (int i = 0; i < subSetIndicator.length; i++) {
if (subSetIndicator[i]) {
// flipping 1 from right to left
subSetIndicator[i] = false;
} else {
// found zero: flip to 1
subSetIndicator[i] = true;
break;
}
}
}
// generating subset
ArrayList<ItemT> subset = new ArrayList<ItemT>();
for (int i = 0; i < subSetIndicator.length; i++) {
if (subSetIndicator[i]) {
subset.add(set.get(i));
}
}
return subset;
}
/** Throws an {@link UnsupportedOperationException} since removal is not supported. */
@Override
public void remove() {
throw new UnsupportedOperationException("The 'remove' operation is not supported by power sets!");
}
}