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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) 2011
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;
import java.util.HashMap;
/**
* A heap as used in OPTICS that allows updating entries.
*
* @author Erich Schubert
*
* @param <O> object type
*/
public class UpdatableHeap<O> extends Heap<O> {
/**
* Serial version
*/
private static final long serialVersionUID = 1L;
/**
* Holds the indices in the heap of each element.
*/
private HashMap<O, Integer> index = new HashMap<O, Integer>();
/**
* Simple constructor with default size.
*/
public UpdatableHeap() {
super();
}
/**
* Constructor with predefined size.
*
* @param size Size
*/
public UpdatableHeap(int size) {
super(size);
}
/**
* Constructor with comparator
*
* @param comparator Comparator
*/
public UpdatableHeap(Comparator<? super O> comparator) {
super(comparator);
}
/**
* Constructor with predefined size and comparator
*
* @param size Size
* @param comparator Comparator
*/
public UpdatableHeap(int size, Comparator<? super O> comparator) {
super(size, comparator);
}
@Override
public void clear() {
super.clear();
index.clear();
}
@Override
public synchronized boolean offer(O e) {
Integer pos = index.get(e);
if(pos == null) {
// LoggingUtil.logExpensive(Level.INFO, "Inserting: "+e);
// insert
return super.offer(e);
}
else {
// update
if(compareExternal(e, pos) < 0) {
// LoggingUtil.logExpensive(Level.INFO,
// "Updating value: "+e+" vs. "+castQueueElement(pos));
modCount++;
putInQueue(pos, e);
heapifyUpParent(pos);
// We have changed - return true according to {@link Collection#put}
return true;
}
else {
// LoggingUtil.logExpensive(Level.INFO,
// "Keeping value: "+e+" vs. "+castQueueElement(pos));
// Ignore, no improvement. Return success anyway.
return true;
}
}
}
@Override
protected void putInQueue(int pos, Object e) {
super.putInQueue(pos, e);
// Keep index up to date
if(e != null) {
O n = castQueueElement(pos);
index.put(n, pos);
}
}
@Override
protected synchronized O removeAt(int pos) {
O node = super.removeAt(pos);
// Keep index up to date
index.remove(node);
return node;
}
/**
* Remove the given object from the queue.
*
* @param e Obejct to remove
* @return Existing entry
*/
public O removeObject(O e) {
Integer pos = index.get(e);
if(pos != null) {
return removeAt(pos);
}
else {
return null;
}
}
@Override
public O poll() {
O node = super.poll();
index.remove(node);
return node;
}
}
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