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package de.lmu.ifi.dbs.elki.utilities.datastructures.heap;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2013
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
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/>.
*/
import java.util.Comparator;
/**
* Heap class that is bounded in size from the top. It will keep the bottom
* {@code k} Elements only.
*
* @author Erich Schubert
*
* @param <E> Element type. Should be {@link Comparable} or a {@link Comparator}
* needs to be given.
*/
public class TopBoundedHeap<E> extends Heap<E> {
/**
* Maximum size.
*/
protected int maxsize;
/**
* Constructor with maximum size only.
*
* @param maxsize Maximum size
*/
public TopBoundedHeap(int maxsize) {
this(maxsize, null);
}
/**
* Constructor with maximum size and {@link Comparator}.
*
* @param maxsize Maximum size
* @param comparator Comparator
*/
public TopBoundedHeap(int maxsize, Comparator<? super E> comparator) {
super(maxsize + 1, comparator);
this.maxsize = maxsize;
assert (maxsize > 0);
}
@Override
public void add(E e) {
if (super.size() < maxsize) {
// Just offer.
super.add(e);
return;
}
// Peek at the top element, return if we are worse.
final int comp;
if (comparator == null) {
@SuppressWarnings("unchecked")
Comparable<Object> c = (Comparable<Object>) e;
comp = c.compareTo(queue[0]);
} else {
comp = comparator.compare(e, queue[0]);
}
if (comp < 0) {
return;
}
if (comp == 0) {
handleOverflow(e);
} else {
// Otherwise, replace and repair:
E prev = super.replaceTopElement(e);
handleOverflow(prev);
}
}
/**
* Handle an overflow in the structure. This function can be overridden to get
* overflow treatment.
*
* @param e Overflowing element.
*/
protected void handleOverflow(E e) {
// discard extra element
}
/**
* Get the maximum size.
*
* @return the maximum size
*/
public int getMaxSize() {
return maxsize;
}
}
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