src.it.unimi.dsi.fastutil.objects.ObjectHeapPriorityQueue Maven / Gradle / Ivy
/* Generic definitions */
/* Assertions (useful to generate conditional code) */
/* Current type and class (and size, if applicable) */
/* Value methods */
/* Interfaces (keys) */
/* Interfaces (values) */
/* Abstract implementations (keys) */
/* Abstract implementations (values) */
/* Static containers (keys) */
/* Static containers (values) */
/* Implementations */
/* Synchronized wrappers */
/* Unmodifiable wrappers */
/* Other wrappers */
/* Methods (keys) */
/* Methods (values) */
/* Methods (keys/values) */
/* Methods that have special names depending on keys (but the special names depend on values) */
/* Equality */
/* Object/Reference-only definitions (keys) */
/* Object/Reference-only definitions (values) */
/*
* Copyright (C) 2003-2013 Paolo Boldi and Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package it.unimi.dsi.fastutil.objects;
import java.util.Comparator;
import it.unimi.dsi.fastutil.AbstractPriorityQueue;
import java.util.NoSuchElementException;
/** A type-specific heap-based priority queue.
*
* Instances of this class represent a priority queue using a heap. The heap is enlarged as needed, but
* it is never shrunk. Use the {@link #trim()} method to reduce its size, if necessary.
*/
public class ObjectHeapPriorityQueue extends AbstractPriorityQueue {
/** The heap array. */
@SuppressWarnings("unchecked")
protected K[] heap = (K[]) ObjectArrays.EMPTY_ARRAY;
/** The number of elements in this queue. */
protected int size;
/** The type-specific comparator used in this queue. */
protected Comparator c;
/** Creates a new empty queue with a given capacity and comparator.
*
* @param capacity the initial capacity of this queue.
* @param c the comparator used in this queue, or null for the natural order.
*/
@SuppressWarnings("unchecked")
public ObjectHeapPriorityQueue( int capacity, Comparator c ) {
if ( capacity > 0 ) this.heap = (K[]) new Object[ capacity ];
this.c = c;
}
/** Creates a new empty queue with a given capacity and using the natural order.
*
* @param capacity the initial capacity of this queue.
*/
public ObjectHeapPriorityQueue( int capacity ) {
this( capacity, null );
}
/** Creates a new empty queue with a given comparator.
*
* @param c the comparator used in this queue, or null for the natural order.
*/
public ObjectHeapPriorityQueue( Comparator c ) {
this( 0, c );
}
/** Creates a new empty queue using the natural order.
*/
public ObjectHeapPriorityQueue() {
this( 0, null );
}
/** Wraps a given array in a queue using a given comparator.
*
* The queue returned by this method will be backed by the given array.
* The first size element of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of a one by one).
*
* @param a an array.
* @param size the number of elements to be included in the queue.
* @param c the comparator used in this queue, or null for the natural order.
*/
public ObjectHeapPriorityQueue( final K[] a, int size, final Comparator c ) {
this( c );
this.heap = a;
this.size = size;
ObjectHeaps.makeHeap( a, size, c );
}
/** Wraps a given array in a queue using a given comparator.
*
*
The queue returned by this method will be backed by the given array.
* The elements of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of a one by one).
*
* @param a an array.
* @param c the comparator used in this queue, or null for the natural order.
*/
public ObjectHeapPriorityQueue( final K[] a, final Comparator c ) {
this( a, a.length, c );
}
/** Wraps a given array in a queue using the natural order.
*
*
The queue returned by this method will be backed by the given array.
* The first size element of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of a one by one).
*
* @param a an array.
* @param size the number of elements to be included in the queue.
*/
public ObjectHeapPriorityQueue( final K[] a, int size ) {
this( a, size, null );
}
/** Wraps a given array in a queue using the natural order.
*
*
The queue returned by this method will be backed by the given array.
* The elements of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of a one by one).
*
* @param a an array.
*/
public ObjectHeapPriorityQueue( final K[] a ) {
this( a, a.length );
}
@SuppressWarnings("unchecked")
public void enqueue( K x ) {
if ( size == heap.length ) heap = ObjectArrays.grow( heap, size + 1 );
heap[ size++ ] = x;
ObjectHeaps.upHeap( heap, size, size - 1, c );
}
public K dequeue() {
if ( size == 0 ) throw new NoSuchElementException();
final K result = heap[ 0 ];
heap[ 0 ] = heap[ --size ];
heap[ size ] = null;
if ( size != 0 ) ObjectHeaps.downHeap( heap, size, 0, c );
return result;
}
public K first() {
if ( size == 0 ) throw new NoSuchElementException();
return heap[ 0 ];
}
public void changed() {
ObjectHeaps.downHeap( heap, size, 0, c );
}
public int size() { return size; }
public void clear() {
ObjectArrays.fill( heap, 0, size, null );
size = 0;
}
/** Trims the underlying heap array so that it has exactly {@link #size()} elements.
*/
public void trim() {
heap = ObjectArrays.trim( heap, size );
}
public Comparator comparator() { return c; }
}