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/* |
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* @(#)PriorityQueue.java 1.8 05/08/27 |
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* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Sun designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Sun in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package java.util; |
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import java.util.*; // for javadoc (till 6280605 is fixed) |
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/** |
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* An unbounded priority {@linkplain Queue queue} based on a priority |
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* heap. The elements of the priority queue are ordered according to |
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* their {@linkplain Comparable natural ordering}, or by a {@link |
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* Comparator} provided at queue construction time, depending on which |
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* constructor is used. A priority queue does not permit |
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* <tt>null</tt> elements. A priority queue relying on natural |
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* ordering also does not permit insertion of non-comparable objects |
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* (doing so may result in <tt>ClassCastException</tt>). |
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* An unbounded priority {@linkplain Queue queue} based on a priority heap. |
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* The elements of the priority queue are ordered according to their |
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* {@linkplain Comparable natural ordering}, or by a {@link Comparator} |
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* provided at queue construction time, depending on which constructor is |
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* used. A priority queue does not permit {@code null} elements. |
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* A priority queue relying on natural ordering also does not permit |
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* insertion of non-comparable objects (doing so may result in |
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* {@code ClassCastException}). |
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* |
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* <p>The <em>head</em> of this queue is the <em>least</em> element |
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* with respect to the specified ordering. If multiple elements are |
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* tied for least value, the head is one of those elements -- ties are |
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* broken arbitrarily. The queue retrieval operations <tt>poll</tt>, |
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* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the |
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* broken arbitrarily. The queue retrieval operations {@code poll}, |
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* {@code remove}, {@code peek}, and {@code element} access the |
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* element at the head of the queue. |
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* |
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* <p>A priority queue is unbounded, but has an internal |
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* Iterator} interfaces. The Iterator provided in method {@link |
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* #iterator()} is <em>not</em> guaranteed to traverse the elements of |
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* the priority queue in any particular order. If you need ordered |
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* traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>. |
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* traversal, consider using {@code Arrays.sort(pq.toArray())}. |
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* |
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* <p> <strong>Note that this implementation is not synchronized.</strong> |
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* Multiple threads should not access a <tt>PriorityQueue</tt> |
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* instance concurrently if any of the threads modifies the list |
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* structurally. Instead, use the thread-safe {@link |
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* Multiple threads should not access a {@code PriorityQueue} |
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* instance concurrently if any of the threads modifies the queue. |
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* Instead, use the thread-safe {@link |
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* java.util.concurrent.PriorityBlockingQueue} class. |
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* |
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* <p>Implementation note: this implementation provides O(log(n)) time |
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* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>, |
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* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the |
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* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and |
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* constant time for the retrieval methods (<tt>peek</tt>, |
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* <tt>element</tt>, and <tt>size</tt>). |
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* <p>Implementation note: this implementation provides |
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* O(log(n)) time for the enqueing and dequeing methods |
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* ({@code offer}, {@code poll}, {@code remove()} and {@code add}); |
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* linear time for the {@code remove(Object)} and {@code contains(Object)} |
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* methods; and constant time for the retrieval methods |
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* ({@code peek}, {@code element}, and {@code size}). |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.5 |
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* @version 1.8, 08/27/05 |
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* @author Josh Bloch |
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* @author Josh Bloch, Doug Lea |
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* @param <E> the type of elements held in this collection |
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*/ |
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@SuppressWarnings("unchecked") |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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implements java.io.Serializable { |
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private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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|
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/** |
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* Priority queue represented as a balanced binary heap: the two children |
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* of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is |
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* ordered by comparator, or by the elements' natural ordering, if |
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* comparator is null: For each node n in the heap and each descendant d |
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* of n, n <= d. |
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* |
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* The element with the lowest value is in queue[1], assuming the queue is |
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* nonempty. (A one-based array is used in preference to the traditional |
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* zero-based array to simplify parent and child calculations.) |
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* |
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* queue.length must be >= 2, even if size == 0. |
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* Priority queue represented as a balanced binary heap: the two |
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* children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The |
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* priority queue is ordered by comparator, or by the elements' |
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* natural ordering, if comparator is null: For each node n in the |
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* heap and each descendant d of n, n <= d. The element with the |
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* lowest value is in queue[0], assuming the queue is nonempty. |
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*/ |
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private transient Object[] queue; |
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private transient int modCount = 0; |
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/** |
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* Creates a <tt>PriorityQueue</tt> with the default initial |
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* Creates a {@code PriorityQueue} with the default initial |
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* capacity (11) that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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*/ |
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} |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> with the specified initial |
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* Creates a {@code PriorityQueue} with the specified initial |
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* capacity that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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* |
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* @param initialCapacity the initial capacity for this priority queue |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
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* than 1 |
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* @throws IllegalArgumentException if {@code initialCapacity} is less |
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* than 1 |
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*/ |
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public PriorityQueue(int initialCapacity) { |
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this(initialCapacity, null); |
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} |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
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* Creates a {@code PriorityQueue} with the specified initial capacity |
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* that orders its elements according to the specified comparator. |
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* |
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* @param initialCapacity the initial capacity for this priority queue |
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* @param comparator the comparator that will be used to order |
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* this priority queue. If <tt>null</tt>, the <i>natural |
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* ordering</i> of the elements will be used. |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is |
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* @param comparator the comparator that will be used to order this |
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* priority queue. If {@code null}, the {@linkplain Comparable |
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* natural ordering} of the elements will be used. |
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* @throws IllegalArgumentException if {@code initialCapacity} is |
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* less than 1 |
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*/ |
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public PriorityQueue(int initialCapacity, |
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Comparator<? super E> comparator) { |
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// Note: This restriction of at least one is not actually needed, |
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// but continues for 1.5 compatibility |
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if (initialCapacity < 1) |
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throw new IllegalArgumentException(); |
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this.queue = new Object[initialCapacity + 1]; |
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this.queue = new Object[initialCapacity]; |
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this.comparator = comparator; |
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} |
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|
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/** |
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* Common code to initialize underlying queue array across |
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* constructors below. |
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*/ |
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private void initializeArray(Collection<? extends E> c) { |
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int sz = c.size(); |
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int initialCapacity = (int)Math.min((sz * 110L) / 100, |
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Integer.MAX_VALUE - 1); |
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if (initialCapacity < 1) |
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initialCapacity = 1; |
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|
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this.queue = new Object[initialCapacity + 1]; |
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} |
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|
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/** |
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* Initially fill elements of the queue array under the |
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* knowledge that it is sorted or is another PQ, in which |
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* case we can just place the elements in the order presented. |
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*/ |
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private void fillFromSorted(Collection<? extends E> c) { |
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) { |
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int k = ++size; |
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if (k >= queue.length) |
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grow(k); |
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queue[k] = i.next(); |
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} |
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} |
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|
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/** |
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* Initially fill elements of the queue array that is not to our knowledge |
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* sorted, so we must rearrange the elements to guarantee the heap |
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* invariant. |
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*/ |
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private void fillFromUnsorted(Collection<? extends E> c) { |
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) { |
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int k = ++size; |
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if (k >= queue.length) |
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grow(k); |
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queue[k] = i.next(); |
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} |
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heapify(); |
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} |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified collection. The priority queue has an initial |
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* capacity of 110% of the size of the specified collection or 1 |
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* if the collection is empty. If the specified collection is an |
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* instance of a {@link java.util.SortedSet} or is another |
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* <tt>PriorityQueue</tt>, the priority queue will be ordered |
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* according to the same ordering. Otherwise, this priority queue |
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* will be ordered according to the natural ordering of its elements. |
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* Creates a {@code PriorityQueue} containing the elements in the |
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* specified collection. If the specified collection is an instance of |
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* a {@link SortedSet} or is another {@code PriorityQueue}, this |
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* priority queue will be ordered according to the same ordering. |
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* Otherwise, this priority queue will be ordered according to the |
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* {@linkplain Comparable natural ordering} of its elements. |
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* |
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* @param c the collection whose elements are to be placed |
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* into this priority queue |
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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(Collection<? extends E> c) { |
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initializeArray(c); |
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if (c instanceof SortedSet) { |
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SortedSet<? extends E> s = (SortedSet<? extends E>)c; |
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comparator = (Comparator<? super E>)s.comparator(); |
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fillFromSorted(s); |
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} else if (c instanceof PriorityQueue) { |
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PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c; |
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comparator = (Comparator<? super E>)s.comparator(); |
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fillFromSorted(s); |
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} else { |
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comparator = null; |
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fillFromUnsorted(c); |
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if (c instanceof SortedSet<?>) { |
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SortedSet<? extends E> ss = (SortedSet<? extends E>) c; |
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this.comparator = (Comparator<? super E>) ss.comparator(); |
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initElementsFromCollection(ss); |
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} |
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else if (c instanceof PriorityQueue<?>) { |
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PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c; |
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this.comparator = (Comparator<? super E>) pq.comparator(); |
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initFromPriorityQueue(pq); |
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} |
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else { |
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this.comparator = null; |
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initFromCollection(c); |
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} |
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} |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified priority queue. The priority queue has an initial |
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* capacity of 110% of the size of the specified priority queue or |
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* 1 if the priority queue is empty. This priority queue will be |
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* Creates a {@code PriorityQueue} containing the elements in the |
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* specified priority queue. This priority queue will be |
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* ordered according to the same ordering as the given priority |
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* queue. |
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* |
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* @param c the priority queue whose elements are to be placed |
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* into this priority queue |
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* @throws ClassCastException if elements of <tt>c</tt> cannot be |
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* compared to one another according to <tt>c</tt>'s |
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* @throws ClassCastException if elements of {@code c} cannot be |
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* compared to one another according to {@code c}'s |
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* ordering |
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* @throws NullPointerException if the specified priority queue or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(PriorityQueue<? extends E> c) { |
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initializeArray(c); |
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comparator = (Comparator<? super E>)c.comparator(); |
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fillFromSorted(c); |
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this.comparator = (Comparator<? super E>) c.comparator(); |
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initFromPriorityQueue(c); |
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} |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified sorted set. The priority queue has an initial |
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* capacity of 110% of the size of the specified sorted set or 1 |
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* if the sorted set is empty. This priority queue will be ordered |
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* Creates a {@code PriorityQueue} containing the elements in the |
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* specified sorted set. This priority queue will be ordered |
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* according to the same ordering as the given sorted set. |
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* |
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* @param c the sorted set whose elements are to be placed |
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* into this priority queue. |
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* into this priority queue |
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* @throws ClassCastException if elements of the specified sorted |
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* set cannot be compared to one another according to the |
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* sorted set's ordering |
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* @throws NullPointerException if the specified sorted set or any |
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* of its elements are null |
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*/ |
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@SuppressWarnings("unchecked") |
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public PriorityQueue(SortedSet<? extends E> c) { |
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initializeArray(c); |
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comparator = (Comparator<? super E>)c.comparator(); |
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fillFromSorted(c); |
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this.comparator = (Comparator<? super E>) c.comparator(); |
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initElementsFromCollection(c); |
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} |
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|
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private void initFromPriorityQueue(PriorityQueue<? extends E> c) { |
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if (c.getClass() == PriorityQueue.class) { |
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this.queue = c.toArray(); |
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this.size = c.size(); |
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} else { |
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initFromCollection(c); |
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} |
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} |
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|
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private void initElementsFromCollection(Collection<? extends E> c) { |
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Object[] a = c.toArray(); |
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// If c.toArray incorrectly doesn't return Object[], copy it. |
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if (a.getClass() != Object[].class) |
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a = Arrays.copyOf(a, a.length, Object[].class); |
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> |
int len = a.length; |
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> |
if (len == 1 || this.comparator != null) |
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for (int i = 0; i < len; i++) |
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if (a[i] == null) |
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throw new NullPointerException(); |
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this.queue = a; |
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this.size = a.length; |
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} |
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|
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> |
/** |
255 |
> |
* Initializes queue array with elements from the given Collection. |
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* |
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* @param c the collection |
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*/ |
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> |
private void initFromCollection(Collection<? extends E> c) { |
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initElementsFromCollection(c); |
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heapify(); |
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} |
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|
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/** |
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* Resize array, if necessary, to be able to hold given index. |
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* The maximum size of array to allocate. |
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* Some VMs reserve some header words in an array. |
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* Attempts to allocate larger arrays may result in |
268 |
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* OutOfMemoryError: Requested array size exceeds VM limit |
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*/ |
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private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
271 |
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|
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> |
/** |
273 |
> |
* Increases the capacity of the array. |
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* |
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* @param minCapacity the desired minimum capacity |
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*/ |
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< |
private void grow(int index) { |
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int newlen = queue.length; |
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if (index < newlen) // don't need to grow |
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return; |
281 |
< |
if (index == Integer.MAX_VALUE) |
277 |
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private void grow(int minCapacity) { |
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> |
int oldCapacity = queue.length; |
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// Double size if small; else grow by 50% |
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int newCapacity = oldCapacity + ((oldCapacity < 64) ? |
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> |
(oldCapacity + 2) : |
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> |
(oldCapacity >> 1)); |
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// overflow-conscious code |
284 |
> |
if (newCapacity - MAX_ARRAY_SIZE > 0) |
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> |
newCapacity = hugeCapacity(minCapacity); |
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queue = Arrays.copyOf(queue, newCapacity); |
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} |
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|
289 |
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private static int hugeCapacity(int minCapacity) { |
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if (minCapacity < 0) // overflow |
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throw new OutOfMemoryError(); |
292 |
< |
while (newlen <= index) { |
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< |
if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow |
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< |
newlen = Integer.MAX_VALUE; |
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else |
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< |
newlen <<= 2; |
277 |
< |
} |
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queue = Arrays.copyOf(queue, newlen); |
292 |
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return (minCapacity > MAX_ARRAY_SIZE) ? |
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Integer.MAX_VALUE : |
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MAX_ARRAY_SIZE; |
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} |
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|
|
297 |
|
/** |
298 |
|
* Inserts the specified element into this priority queue. |
299 |
|
* |
300 |
< |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
300 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
301 |
|
* @throws ClassCastException if the specified element cannot be |
302 |
|
* compared with elements currently in this priority queue |
303 |
|
* according to the priority queue's ordering |
310 |
|
/** |
311 |
|
* Inserts the specified element into this priority queue. |
312 |
|
* |
313 |
< |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
313 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
314 |
|
* @throws ClassCastException if the specified element cannot be |
315 |
|
* compared with elements currently in this priority queue |
316 |
|
* according to the priority queue's ordering |
320 |
|
if (e == null) |
321 |
|
throw new NullPointerException(); |
322 |
|
modCount++; |
323 |
< |
++size; |
324 |
< |
|
325 |
< |
// Grow backing store if necessary |
326 |
< |
if (size >= queue.length) |
327 |
< |
grow(size); |
328 |
< |
|
329 |
< |
queue[size] = e; |
330 |
< |
fixUp(size); |
323 |
> |
int i = size; |
324 |
> |
if (i >= queue.length) |
325 |
> |
grow(i + 1); |
326 |
> |
size = i + 1; |
327 |
> |
if (i == 0) |
328 |
> |
queue[0] = e; |
329 |
> |
else |
330 |
> |
siftUp(i, e); |
331 |
|
return true; |
332 |
|
} |
333 |
|
|
334 |
|
public E peek() { |
335 |
< |
if (size == 0) |
320 |
< |
return null; |
321 |
< |
return (E) queue[1]; |
335 |
> |
return (size == 0) ? null : (E) queue[0]; |
336 |
|
} |
337 |
|
|
338 |
|
private int indexOf(Object o) { |
339 |
< |
if (o == null) |
340 |
< |
return -1; |
341 |
< |
for (int i = 1; i <= size; i++) |
342 |
< |
if (o.equals(queue[i])) |
343 |
< |
return i; |
339 |
> |
if (o != null) { |
340 |
> |
for (int i = 0; i < size; i++) |
341 |
> |
if (o.equals(queue[i])) |
342 |
> |
return i; |
343 |
> |
} |
344 |
|
return -1; |
345 |
|
} |
346 |
|
|
347 |
|
/** |
348 |
|
* Removes a single instance of the specified element from this queue, |
349 |
< |
* if it is present. More formally, removes an element <tt>e</tt> such |
350 |
< |
* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
351 |
< |
* elements. Returns true if this queue contained the specified element |
352 |
< |
* (or equivalently, if this queue changed as a result of the call). |
349 |
> |
* if it is present. More formally, removes an element {@code e} such |
350 |
> |
* that {@code o.equals(e)}, if this queue contains one or more such |
351 |
> |
* elements. Returns {@code true} if and only if this queue contained |
352 |
> |
* the specified element (or equivalently, if this queue changed as a |
353 |
> |
* result of the call). |
354 |
|
* |
355 |
|
* @param o element to be removed from this queue, if present |
356 |
< |
* @return <tt>true</tt> if this queue changed as a result of the call |
356 |
> |
* @return {@code true} if this queue changed as a result of the call |
357 |
|
*/ |
358 |
|
public boolean remove(Object o) { |
359 |
< |
int i = indexOf(o); |
360 |
< |
if (i == -1) |
361 |
< |
return false; |
362 |
< |
else { |
363 |
< |
removeAt(i); |
364 |
< |
return true; |
365 |
< |
} |
359 |
> |
int i = indexOf(o); |
360 |
> |
if (i == -1) |
361 |
> |
return false; |
362 |
> |
else { |
363 |
> |
removeAt(i); |
364 |
> |
return true; |
365 |
> |
} |
366 |
|
} |
367 |
|
|
368 |
|
/** |
369 |
< |
* Returns <tt>true</tt> if this queue contains the specified element. |
370 |
< |
* More formally, returns <tt>true</tt> if and only if this queue contains |
371 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
369 |
> |
* Version of remove using reference equality, not equals. |
370 |
> |
* Needed by iterator.remove. |
371 |
> |
* |
372 |
> |
* @param o element to be removed from this queue, if present |
373 |
> |
* @return {@code true} if removed |
374 |
> |
*/ |
375 |
> |
boolean removeEq(Object o) { |
376 |
> |
for (int i = 0; i < size; i++) { |
377 |
> |
if (o == queue[i]) { |
378 |
> |
removeAt(i); |
379 |
> |
return true; |
380 |
> |
} |
381 |
> |
} |
382 |
> |
return false; |
383 |
> |
} |
384 |
> |
|
385 |
> |
/** |
386 |
> |
* Returns {@code true} if this queue contains the specified element. |
387 |
> |
* More formally, returns {@code true} if and only if this queue contains |
388 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
389 |
|
* |
390 |
|
* @param o object to be checked for containment in this queue |
391 |
< |
* @return <tt>true</tt> if this queue contains the specified element |
391 |
> |
* @return {@code true} if this queue contains the specified element |
392 |
|
*/ |
393 |
|
public boolean contains(Object o) { |
394 |
< |
return indexOf(o) != -1; |
394 |
> |
return indexOf(o) != -1; |
395 |
|
} |
396 |
|
|
397 |
|
/** |
398 |
< |
* Returns an array containing all of the elements in this queue, |
398 |
> |
* Returns an array containing all of the elements in this queue. |
399 |
|
* The elements are in no particular order. |
400 |
|
* |
401 |
|
* <p>The returned array will be "safe" in that no references to it are |
402 |
< |
* maintained by this list. (In other words, this method must allocate |
402 |
> |
* maintained by this queue. (In other words, this method must allocate |
403 |
|
* a new array). The caller is thus free to modify the returned array. |
404 |
|
* |
405 |
< |
* @return an array containing all of the elements in this queue. |
405 |
> |
* <p>This method acts as bridge between array-based and collection-based |
406 |
> |
* APIs. |
407 |
> |
* |
408 |
> |
* @return an array containing all of the elements in this queue |
409 |
|
*/ |
410 |
|
public Object[] toArray() { |
411 |
< |
return Arrays.copyOfRange(queue, 1, size+1); |
411 |
> |
return Arrays.copyOf(queue, size); |
412 |
|
} |
413 |
|
|
414 |
|
/** |
415 |
< |
* Returns an array containing all of the elements in this queue. |
416 |
< |
* The elements are in no particular order. The runtime type of |
417 |
< |
* the returned array is that of the specified array. If the queue |
418 |
< |
* fits in the specified array, it is returned therein. |
419 |
< |
* Otherwise, a new array is allocated with the runtime type of |
420 |
< |
* the specified array and the size of this queue. |
415 |
> |
* Returns an array containing all of the elements in this queue; the |
416 |
> |
* runtime type of the returned array is that of the specified array. |
417 |
> |
* The returned array elements are in no particular order. |
418 |
> |
* If the queue fits in the specified array, it is returned therein. |
419 |
> |
* Otherwise, a new array is allocated with the runtime type of the |
420 |
> |
* specified array and the size of this queue. |
421 |
|
* |
422 |
|
* <p>If the queue fits in the specified array with room to spare |
423 |
|
* (i.e., the array has more elements than the queue), the element in |
424 |
|
* the array immediately following the end of the collection is set to |
425 |
< |
* <tt>null</tt>. (This is useful in determining the length of the |
426 |
< |
* queue <i>only</i> if the caller knows that the queue does not contain |
427 |
< |
* any null elements.) |
425 |
> |
* {@code null}. |
426 |
> |
* |
427 |
> |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
428 |
> |
* array-based and collection-based APIs. Further, this method allows |
429 |
> |
* precise control over the runtime type of the output array, and may, |
430 |
> |
* under certain circumstances, be used to save allocation costs. |
431 |
> |
* |
432 |
> |
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
433 |
> |
* The following code can be used to dump the queue into a newly |
434 |
> |
* allocated array of <tt>String</tt>: |
435 |
> |
* |
436 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
437 |
> |
* |
438 |
> |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
439 |
> |
* <tt>toArray()</tt>. |
440 |
|
* |
441 |
|
* @param a the array into which the elements of the queue are to |
442 |
|
* be stored, if it is big enough; otherwise, a new array of the |
443 |
|
* same runtime type is allocated for this purpose. |
444 |
< |
* @return an array containing the elements of the queue |
444 |
> |
* @return an array containing all of the elements in this queue |
445 |
|
* @throws ArrayStoreException if the runtime type of the specified array |
446 |
|
* is not a supertype of the runtime type of every element in |
447 |
|
* this queue |
450 |
|
public <T> T[] toArray(T[] a) { |
451 |
|
if (a.length < size) |
452 |
|
// Make a new array of a's runtime type, but my contents: |
453 |
< |
return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass()); |
454 |
< |
System.arraycopy(queue, 1, a, 0, size); |
453 |
> |
return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
454 |
> |
System.arraycopy(queue, 0, a, 0, size); |
455 |
|
if (a.length > size) |
456 |
|
a[size] = null; |
457 |
|
return a; |
467 |
|
return new Itr(); |
468 |
|
} |
469 |
|
|
470 |
< |
private class Itr implements Iterator<E> { |
424 |
< |
|
470 |
> |
private final class Itr implements Iterator<E> { |
471 |
|
/** |
472 |
|
* Index (into queue array) of element to be returned by |
473 |
|
* subsequent call to next. |
474 |
|
*/ |
475 |
< |
private int cursor = 1; |
475 |
> |
private int cursor = 0; |
476 |
|
|
477 |
|
/** |
478 |
|
* Index of element returned by most recent call to next, |
479 |
|
* unless that element came from the forgetMeNot list. |
480 |
< |
* Reset to 0 if element is deleted by a call to remove. |
480 |
> |
* Set to -1 if element is deleted by a call to remove. |
481 |
|
*/ |
482 |
< |
private int lastRet = 0; |
482 |
> |
private int lastRet = -1; |
483 |
|
|
484 |
|
/** |
485 |
< |
* The modCount value that the iterator believes that the backing |
440 |
< |
* List should have. If this expectation is violated, the iterator |
441 |
< |
* has detected concurrent modification. |
442 |
< |
*/ |
443 |
< |
private int expectedModCount = modCount; |
444 |
< |
|
445 |
< |
/** |
446 |
< |
* A list of elements that were moved from the unvisited portion of |
485 |
> |
* A queue of elements that were moved from the unvisited portion of |
486 |
|
* the heap into the visited portion as a result of "unlucky" element |
487 |
|
* removals during the iteration. (Unlucky element removals are those |
488 |
< |
* that require a fixup instead of a fixdown.) We must visit all of |
488 |
> |
* that require a siftup instead of a siftdown.) We must visit all of |
489 |
|
* the elements in this list to complete the iteration. We do this |
490 |
|
* after we've completed the "normal" iteration. |
491 |
|
* |
492 |
|
* We expect that most iterations, even those involving removals, |
493 |
< |
* will not use need to store elements in this field. |
493 |
> |
* will not need to store elements in this field. |
494 |
|
*/ |
495 |
< |
private ArrayList<E> forgetMeNot = null; |
495 |
> |
private ArrayDeque<E> forgetMeNot = null; |
496 |
|
|
497 |
|
/** |
498 |
|
* Element returned by the most recent call to next iff that |
499 |
|
* element was drawn from the forgetMeNot list. |
500 |
|
*/ |
501 |
< |
private Object lastRetElt = null; |
501 |
> |
private E lastRetElt = null; |
502 |
> |
|
503 |
> |
/** |
504 |
> |
* The modCount value that the iterator believes that the backing |
505 |
> |
* Queue should have. If this expectation is violated, the iterator |
506 |
> |
* has detected concurrent modification. |
507 |
> |
*/ |
508 |
> |
private int expectedModCount = modCount; |
509 |
|
|
510 |
|
public boolean hasNext() { |
511 |
< |
return cursor <= size || forgetMeNot != null; |
511 |
> |
return cursor < size || |
512 |
> |
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
513 |
|
} |
514 |
|
|
515 |
|
public E next() { |
516 |
< |
checkForComodification(); |
517 |
< |
E result; |
518 |
< |
if (cursor <= size) { |
519 |
< |
result = (E) queue[cursor]; |
520 |
< |
lastRet = cursor++; |
521 |
< |
} |
522 |
< |
else if (forgetMeNot == null) |
523 |
< |
throw new NoSuchElementException(); |
524 |
< |
else { |
478 |
< |
int remaining = forgetMeNot.size(); |
479 |
< |
result = forgetMeNot.remove(remaining - 1); |
480 |
< |
if (remaining == 1) |
481 |
< |
forgetMeNot = null; |
482 |
< |
lastRet = 0; |
483 |
< |
lastRetElt = result; |
516 |
> |
if (expectedModCount != modCount) |
517 |
> |
throw new ConcurrentModificationException(); |
518 |
> |
if (cursor < size) |
519 |
> |
return (E) queue[lastRet = cursor++]; |
520 |
> |
if (forgetMeNot != null) { |
521 |
> |
lastRet = -1; |
522 |
> |
lastRetElt = forgetMeNot.poll(); |
523 |
> |
if (lastRetElt != null) |
524 |
> |
return lastRetElt; |
525 |
|
} |
526 |
< |
return result; |
526 |
> |
throw new NoSuchElementException(); |
527 |
|
} |
528 |
|
|
529 |
|
public void remove() { |
530 |
< |
checkForComodification(); |
531 |
< |
|
532 |
< |
if (lastRet != 0) { |
530 |
> |
if (expectedModCount != modCount) |
531 |
> |
throw new ConcurrentModificationException(); |
532 |
> |
if (lastRet != -1) { |
533 |
|
E moved = PriorityQueue.this.removeAt(lastRet); |
534 |
< |
lastRet = 0; |
535 |
< |
if (moved == null) { |
534 |
> |
lastRet = -1; |
535 |
> |
if (moved == null) |
536 |
|
cursor--; |
537 |
< |
} else { |
537 |
> |
else { |
538 |
|
if (forgetMeNot == null) |
539 |
< |
forgetMeNot = new ArrayList<E>(); |
539 |
> |
forgetMeNot = new ArrayDeque<E>(); |
540 |
|
forgetMeNot.add(moved); |
541 |
|
} |
542 |
|
} else if (lastRetElt != null) { |
543 |
< |
PriorityQueue.this.remove(lastRetElt); |
543 |
> |
PriorityQueue.this.removeEq(lastRetElt); |
544 |
|
lastRetElt = null; |
545 |
|
} else { |
546 |
|
throw new IllegalStateException(); |
547 |
|
} |
507 |
– |
|
548 |
|
expectedModCount = modCount; |
549 |
|
} |
510 |
– |
|
511 |
– |
final void checkForComodification() { |
512 |
– |
if (modCount != expectedModCount) |
513 |
– |
throw new ConcurrentModificationException(); |
514 |
– |
} |
550 |
|
} |
551 |
|
|
552 |
|
public int size() { |
559 |
|
*/ |
560 |
|
public void clear() { |
561 |
|
modCount++; |
562 |
< |
|
528 |
< |
// Null out element references to prevent memory leak |
529 |
< |
for (int i=1; i<=size; i++) |
562 |
> |
for (int i = 0; i < size; i++) |
563 |
|
queue[i] = null; |
531 |
– |
|
564 |
|
size = 0; |
565 |
|
} |
566 |
|
|
567 |
|
public E poll() { |
568 |
|
if (size == 0) |
569 |
|
return null; |
570 |
+ |
int s = --size; |
571 |
|
modCount++; |
572 |
< |
|
573 |
< |
E result = (E) queue[1]; |
574 |
< |
queue[1] = queue[size]; |
575 |
< |
queue[size--] = null; // Drop extra ref to prevent memory leak |
576 |
< |
if (size > 1) |
544 |
< |
fixDown(1); |
545 |
< |
|
572 |
> |
E result = (E) queue[0]; |
573 |
> |
E x = (E) queue[s]; |
574 |
> |
queue[s] = null; |
575 |
> |
if (s != 0) |
576 |
> |
siftDown(0, x); |
577 |
|
return result; |
578 |
|
} |
579 |
|
|
580 |
|
/** |
581 |
< |
* Removes and returns the ith element from queue. (Recall that queue |
551 |
< |
* is one-based, so 1 <= i <= size.) |
581 |
> |
* Removes the ith element from queue. |
582 |
|
* |
583 |
< |
* Normally this method leaves the elements at positions from 1 up to i-1, |
584 |
< |
* inclusive, untouched. Under these circumstances, it returns null. |
585 |
< |
* Occasionally, in order to maintain the heap invariant, it must move |
586 |
< |
* the last element of the list to some index in the range [2, i-1], |
587 |
< |
* and move the element previously at position (i/2) to position i. |
588 |
< |
* Under these circumstances, this method returns the element that was |
589 |
< |
* previously at the end of the list and is now at some position between |
590 |
< |
* 2 and i-1 inclusive. |
583 |
> |
* Normally this method leaves the elements at up to i-1, |
584 |
> |
* inclusive, untouched. Under these circumstances, it returns |
585 |
> |
* null. Occasionally, in order to maintain the heap invariant, |
586 |
> |
* it must swap a later element of the list with one earlier than |
587 |
> |
* i. Under these circumstances, this method returns the element |
588 |
> |
* that was previously at the end of the list and is now at some |
589 |
> |
* position before i. This fact is used by iterator.remove so as to |
590 |
> |
* avoid missing traversing elements. |
591 |
|
*/ |
592 |
|
private E removeAt(int i) { |
593 |
< |
assert i > 0 && i <= size; |
593 |
> |
// assert i >= 0 && i < size; |
594 |
|
modCount++; |
595 |
< |
|
596 |
< |
E moved = (E) queue[size]; |
597 |
< |
queue[i] = moved; |
598 |
< |
queue[size--] = null; // Drop extra ref to prevent memory leak |
599 |
< |
if (i <= size) { |
600 |
< |
fixDown(i); |
595 |
> |
int s = --size; |
596 |
> |
if (s == i) // removed last element |
597 |
> |
queue[i] = null; |
598 |
> |
else { |
599 |
> |
E moved = (E) queue[s]; |
600 |
> |
queue[s] = null; |
601 |
> |
siftDown(i, moved); |
602 |
|
if (queue[i] == moved) { |
603 |
< |
fixUp(i); |
603 |
> |
siftUp(i, moved); |
604 |
|
if (queue[i] != moved) |
605 |
|
return moved; |
606 |
|
} |
609 |
|
} |
610 |
|
|
611 |
|
/** |
612 |
< |
* Establishes the heap invariant (described above) assuming the heap |
613 |
< |
* satisfies the invariant except possibly for the leaf-node indexed by k |
614 |
< |
* (which may have a nextExecutionTime less than its parent's). |
615 |
< |
* |
616 |
< |
* This method functions by "promoting" queue[k] up the hierarchy |
617 |
< |
* (by swapping it with its parent) repeatedly until queue[k] |
618 |
< |
* is greater than or equal to its parent. |
619 |
< |
*/ |
620 |
< |
private void fixUp(int k) { |
621 |
< |
if (comparator == null) { |
622 |
< |
while (k > 1) { |
623 |
< |
int j = k >> 1; |
624 |
< |
if (((Comparable<? super E>)queue[j]).compareTo((E)queue[k]) <= 0) |
625 |
< |
break; |
626 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
627 |
< |
k = j; |
628 |
< |
} |
629 |
< |
} else { |
630 |
< |
while (k > 1) { |
631 |
< |
int j = k >>> 1; |
632 |
< |
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
633 |
< |
break; |
634 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
635 |
< |
k = j; |
636 |
< |
} |
637 |
< |
} |
638 |
< |
} |
639 |
< |
|
640 |
< |
/** |
641 |
< |
* Establishes the heap invariant (described above) in the subtree |
642 |
< |
* rooted at k, which is assumed to satisfy the heap invariant except |
643 |
< |
* possibly for node k itself (which may be greater than its children). |
644 |
< |
* |
645 |
< |
* This method functions by "demoting" queue[k] down the hierarchy |
646 |
< |
* (by swapping it with its smaller child) repeatedly until queue[k] |
647 |
< |
* is less than or equal to its children. |
648 |
< |
*/ |
649 |
< |
private void fixDown(int k) { |
650 |
< |
int j; |
651 |
< |
if (comparator == null) { |
652 |
< |
while ((j = k << 1) <= size && (j > 0)) { |
653 |
< |
if (j<size && |
654 |
< |
((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
655 |
< |
j++; // j indexes smallest kid |
656 |
< |
|
657 |
< |
if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0) |
658 |
< |
break; |
659 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
660 |
< |
k = j; |
661 |
< |
} |
662 |
< |
} else { |
663 |
< |
while ((j = k << 1) <= size && (j > 0)) { |
664 |
< |
if (j<size && |
665 |
< |
comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
666 |
< |
j++; // j indexes smallest kid |
667 |
< |
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
668 |
< |
break; |
669 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
670 |
< |
k = j; |
671 |
< |
} |
612 |
> |
* Inserts item x at position k, maintaining heap invariant by |
613 |
> |
* promoting x up the tree until it is greater than or equal to |
614 |
> |
* its parent, or is the root. |
615 |
> |
* |
616 |
> |
* To simplify and speed up coercions and comparisons. the |
617 |
> |
* Comparable and Comparator versions are separated into different |
618 |
> |
* methods that are otherwise identical. (Similarly for siftDown.) |
619 |
> |
* |
620 |
> |
* @param k the position to fill |
621 |
> |
* @param x the item to insert |
622 |
> |
*/ |
623 |
> |
private void siftUp(int k, E x) { |
624 |
> |
if (comparator != null) |
625 |
> |
siftUpUsingComparator(k, x); |
626 |
> |
else |
627 |
> |
siftUpComparable(k, x); |
628 |
> |
} |
629 |
> |
|
630 |
> |
private void siftUpComparable(int k, E x) { |
631 |
> |
Comparable<? super E> key = (Comparable<? super E>) x; |
632 |
> |
while (k > 0) { |
633 |
> |
int parent = (k - 1) >>> 1; |
634 |
> |
Object e = queue[parent]; |
635 |
> |
if (key.compareTo((E) e) >= 0) |
636 |
> |
break; |
637 |
> |
queue[k] = e; |
638 |
> |
k = parent; |
639 |
> |
} |
640 |
> |
queue[k] = key; |
641 |
> |
} |
642 |
> |
|
643 |
> |
private void siftUpUsingComparator(int k, E x) { |
644 |
> |
while (k > 0) { |
645 |
> |
int parent = (k - 1) >>> 1; |
646 |
> |
Object e = queue[parent]; |
647 |
> |
if (comparator.compare(x, (E) e) >= 0) |
648 |
> |
break; |
649 |
> |
queue[k] = e; |
650 |
> |
k = parent; |
651 |
> |
} |
652 |
> |
queue[k] = x; |
653 |
> |
} |
654 |
> |
|
655 |
> |
/** |
656 |
> |
* Inserts item x at position k, maintaining heap invariant by |
657 |
> |
* demoting x down the tree repeatedly until it is less than or |
658 |
> |
* equal to its children or is a leaf. |
659 |
> |
* |
660 |
> |
* @param k the position to fill |
661 |
> |
* @param x the item to insert |
662 |
> |
*/ |
663 |
> |
private void siftDown(int k, E x) { |
664 |
> |
if (comparator != null) |
665 |
> |
siftDownUsingComparator(k, x); |
666 |
> |
else |
667 |
> |
siftDownComparable(k, x); |
668 |
> |
} |
669 |
> |
|
670 |
> |
private void siftDownComparable(int k, E x) { |
671 |
> |
Comparable<? super E> key = (Comparable<? super E>)x; |
672 |
> |
int half = size >>> 1; // loop while a non-leaf |
673 |
> |
while (k < half) { |
674 |
> |
int child = (k << 1) + 1; // assume left child is least |
675 |
> |
Object c = queue[child]; |
676 |
> |
int right = child + 1; |
677 |
> |
if (right < size && |
678 |
> |
((Comparable<? super E>) c).compareTo((E) queue[right]) > 0) |
679 |
> |
c = queue[child = right]; |
680 |
> |
if (key.compareTo((E) c) <= 0) |
681 |
> |
break; |
682 |
> |
queue[k] = c; |
683 |
> |
k = child; |
684 |
> |
} |
685 |
> |
queue[k] = key; |
686 |
> |
} |
687 |
> |
|
688 |
> |
private void siftDownUsingComparator(int k, E x) { |
689 |
> |
int half = size >>> 1; |
690 |
> |
while (k < half) { |
691 |
> |
int child = (k << 1) + 1; |
692 |
> |
Object c = queue[child]; |
693 |
> |
int right = child + 1; |
694 |
> |
if (right < size && |
695 |
> |
comparator.compare((E) c, (E) queue[right]) > 0) |
696 |
> |
c = queue[child = right]; |
697 |
> |
if (comparator.compare(x, (E) c) <= 0) |
698 |
> |
break; |
699 |
> |
queue[k] = c; |
700 |
> |
k = child; |
701 |
|
} |
702 |
+ |
queue[k] = x; |
703 |
|
} |
704 |
|
|
705 |
|
/** |
707 |
|
* assuming nothing about the order of the elements prior to the call. |
708 |
|
*/ |
709 |
|
private void heapify() { |
710 |
< |
for (int i = size/2; i >= 1; i--) |
711 |
< |
fixDown(i); |
710 |
> |
for (int i = (size >>> 1) - 1; i >= 0; i--) |
711 |
> |
siftDown(i, (E) queue[i]); |
712 |
|
} |
713 |
|
|
714 |
|
/** |
715 |
|
* Returns the comparator used to order the elements in this |
716 |
< |
* queue, or <tt>null</tt> if this queue is sorted according to |
716 |
> |
* queue, or {@code null} if this queue is sorted according to |
717 |
|
* the {@linkplain Comparable natural ordering} of its elements. |
718 |
|
* |
719 |
|
* @return the comparator used to order this queue, or |
720 |
< |
* <tt>null</tt> if this queue is sorted according to the |
721 |
< |
* natural ordering of its elements. |
720 |
> |
* {@code null} if this queue is sorted according to the |
721 |
> |
* natural ordering of its elements |
722 |
|
*/ |
723 |
|
public Comparator<? super E> comparator() { |
724 |
|
return comparator; |
725 |
|
} |
726 |
|
|
727 |
|
/** |
728 |
< |
* Save the state of the instance to a stream (that |
729 |
< |
* is, serialize it). |
728 |
> |
* Saves the state of the instance to a stream (that |
729 |
> |
* is, serializes it). |
730 |
|
* |
731 |
|
* @serialData The length of the array backing the instance is |
732 |
< |
* emitted (int), followed by all of its elements (each an |
733 |
< |
* <tt>Object</tt>) in the proper order. |
732 |
> |
* emitted (int), followed by all of its elements |
733 |
> |
* (each an {@code Object}) in the proper order. |
734 |
|
* @param s the stream |
735 |
|
*/ |
736 |
|
private void writeObject(java.io.ObjectOutputStream s) |
737 |
< |
throws java.io.IOException{ |
737 |
> |
throws java.io.IOException { |
738 |
|
// Write out element count, and any hidden stuff |
739 |
|
s.defaultWriteObject(); |
740 |
|
|
741 |
< |
// Write out array length |
742 |
< |
s.writeInt(queue.length); |
741 |
> |
// Write out array length, for compatibility with 1.5 version |
742 |
> |
s.writeInt(Math.max(2, size + 1)); |
743 |
|
|
744 |
< |
// Write out all elements in the proper order. |
745 |
< |
for (int i=1; i<=size; i++) |
744 |
> |
// Write out all elements in the "proper order". |
745 |
> |
for (int i = 0; i < size; i++) |
746 |
|
s.writeObject(queue[i]); |
747 |
|
} |
748 |
|
|
749 |
|
/** |
750 |
< |
* Reconstitute the <tt>PriorityQueue</tt> instance from a stream |
751 |
< |
* (that is, deserialize it). |
750 |
> |
* Reconstitutes the {@code PriorityQueue} instance from a stream |
751 |
> |
* (that is, deserializes it). |
752 |
> |
* |
753 |
|
* @param s the stream |
754 |
|
*/ |
755 |
|
private void readObject(java.io.ObjectInputStream s) |
757 |
|
// Read in size, and any hidden stuff |
758 |
|
s.defaultReadObject(); |
759 |
|
|
760 |
< |
// Read in array length and allocate array |
761 |
< |
int arrayLength = s.readInt(); |
762 |
< |
queue = new Object[arrayLength]; |
763 |
< |
|
702 |
< |
// Read in all elements in the proper order. |
703 |
< |
for (int i=1; i<=size; i++) |
704 |
< |
queue[i] = (E) s.readObject(); |
705 |
< |
} |
760 |
> |
// Read in (and discard) array length |
761 |
> |
s.readInt(); |
762 |
> |
|
763 |
> |
queue = new Object[size]; |
764 |
|
|
765 |
+ |
// Read in all elements. |
766 |
+ |
for (int i = 0; i < size; i++) |
767 |
+ |
queue[i] = s.readObject(); |
768 |
+ |
|
769 |
+ |
// Elements are guaranteed to be in "proper order", but the |
770 |
+ |
// spec has never explained what that might be. |
771 |
+ |
heapify(); |
772 |
+ |
} |
773 |
|
} |