cross.math.CombinationIterator Maven / Gradle / Ivy
/*
* Cross, common runtime object support system.
* Copyright (C) 2008-2012, The authors of Cross. All rights reserved.
*
* Project website: http://maltcms.sf.net
*
* Cross may be used under the terms of either the
*
* GNU Lesser General Public License (LGPL)
* http://www.gnu.org/licenses/lgpl.html
*
* or the
*
* Eclipse Public License (EPL)
* http://www.eclipse.org/org/documents/epl-v10.php
*
* As a user/recipient of Cross, you may choose which license to receive the code
* under. Certain files or entire directories may not be covered by this
* dual license, but are subject to licenses compatible to both LGPL and EPL.
* License exceptions are explicitly declared in all relevant files or in a
* LICENSE file in the relevant directories.
*
* Cross 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. Please consult the relevant license documentation
* for details.
*/
package cross.math;
import java.util.Iterator;
/**
* Implementation of {@link Iterator} for int[], returning, for a
* given number of {@link Partition}s in increasing order, an array of item
* indices for each partition for the current iteration. Allows to enumerate
* all items of supplied partitions of arbitrary size in a defined order.
*
* @author Nils Hoffmann
*/
public final class CombinationIterator implements Iterator {
private final Partition[] partitions;
private long size = -1;
private long cnt = 0;
/**
* Create a new CombinationIterator with given Partitions.
*
* @param p
*/
public CombinationIterator(Partition... p) {
this.partitions = p;
this.size = size();
}
/**
*
* @return
*/
@Override
public boolean hasNext() {
if (cnt < size) {
return true;
}
return false;
}
/**
*
* @return
*/
@Override
public int[] next() {
int[] ret = new int[this.partitions.length];
for (int i = 0; i < ret.length; i++) {
ret[i] = partitions[i].current();
}
partitions[this.partitions.length - 1].next();
cnt++;
return ret;
}
/**
* @throws UnsupportedOperationException
*/
@Override
public void remove() {
throw new UnsupportedOperationException("Not supported yet.");
}
/**
* Returns the number of combinations of all partitions and their elements.
*
* @return the size
*/
public long size() {
if (this.size == -1) {
long size = 1;
for (Partition p : partitions) {
size *= p.size();
}
this.size = size;
}
return size;
}
/**
* Resets the iterator to initial value.
*/
public void reset() {
this.cnt = 0;
for (Partition p : partitions) {
p.reset();
}
}
}