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/*
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* Copyright (c) 2003, 2010, 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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* 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. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle 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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/**
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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 {@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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* <i>capacity</i> governing the size of an array used to store the
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* elements on the queue. It is always at least as large as the queue
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* size. As elements are added to a priority queue, its capacity
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* grows automatically. The details of the growth policy are not
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* specified.
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*
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* <p>This class and its iterator implement all of the
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* <em>optional</em> methods of the {@link Collection} and {@link
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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 {@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 {@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
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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}/../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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* @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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public class PriorityQueue<E> extends AbstractQueue<E>
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implements java.io.Serializable {
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private static final long serialVersionUID = -7720805057305804111L;
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private static final int DEFAULT_INITIAL_CAPACITY = 11;
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/**
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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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/**
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* The number of elements in the priority queue.
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*/
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private int size = 0;
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/**
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* The comparator, or null if priority queue uses elements'
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* natural ordering.
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*/
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private final Comparator<? super E> comparator;
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/**
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* The number of times this priority queue has been
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* <i>structurally modified</i>. See AbstractList for gory details.
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*/
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private transient int modCount = 0;
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/**
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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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public PriorityQueue() {
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this(DEFAULT_INITIAL_CAPACITY, null);
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}
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/**
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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 {@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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* 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 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];
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this.comparator = comparator;
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}
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/**
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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 ClassCastException if elements of the specified collection
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* cannot be compared to one another according to the priority
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* queue's ordering
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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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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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* 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 {@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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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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* 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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* @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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this.comparator = (Comparator<? super E>) c.comparator();
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initElementsFromCollection(c);
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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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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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* 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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* 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
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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;
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/**
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* 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 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
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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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private static int hugeCapacity(int minCapacity) {
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if (minCapacity < 0) // overflow
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throw new OutOfMemoryError();
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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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/**
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* Inserts the specified element into this priority queue.
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*
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* @return {@code true} (as specified by {@link Collection#add})
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* @throws ClassCastException if the specified element cannot be
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* compared with elements currently in this priority queue
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* according to the priority queue's ordering
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* @throws NullPointerException if the specified element is null
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*/
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public boolean add(E e) {
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return offer(e);
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}
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/**
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* Inserts the specified element into this priority queue.
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*
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|
313 |
* @return {@code true} (as specified by {@link Queue#offer})
|
jaroslav@633
|
314 |
* @throws ClassCastException if the specified element cannot be
|
jaroslav@633
|
315 |
* compared with elements currently in this priority queue
|
jaroslav@633
|
316 |
* according to the priority queue's ordering
|
jaroslav@633
|
317 |
* @throws NullPointerException if the specified element is null
|
jaroslav@633
|
318 |
*/
|
jaroslav@633
|
319 |
public boolean offer(E e) {
|
jaroslav@633
|
320 |
if (e == null)
|
jaroslav@633
|
321 |
throw new NullPointerException();
|
jaroslav@633
|
322 |
modCount++;
|
jaroslav@633
|
323 |
int i = size;
|
jaroslav@633
|
324 |
if (i >= queue.length)
|
jaroslav@633
|
325 |
grow(i + 1);
|
jaroslav@633
|
326 |
size = i + 1;
|
jaroslav@633
|
327 |
if (i == 0)
|
jaroslav@633
|
328 |
queue[0] = e;
|
jaroslav@633
|
329 |
else
|
jaroslav@633
|
330 |
siftUp(i, e);
|
jaroslav@633
|
331 |
return true;
|
jaroslav@633
|
332 |
}
|
jaroslav@633
|
333 |
|
jaroslav@633
|
334 |
public E peek() {
|
jaroslav@633
|
335 |
if (size == 0)
|
jaroslav@633
|
336 |
return null;
|
jaroslav@633
|
337 |
return (E) queue[0];
|
jaroslav@633
|
338 |
}
|
jaroslav@633
|
339 |
|
jaroslav@633
|
340 |
private int indexOf(Object o) {
|
jaroslav@633
|
341 |
if (o != null) {
|
jaroslav@633
|
342 |
for (int i = 0; i < size; i++)
|
jaroslav@633
|
343 |
if (o.equals(queue[i]))
|
jaroslav@633
|
344 |
return i;
|
jaroslav@633
|
345 |
}
|
jaroslav@633
|
346 |
return -1;
|
jaroslav@633
|
347 |
}
|
jaroslav@633
|
348 |
|
jaroslav@633
|
349 |
/**
|
jaroslav@633
|
350 |
* Removes a single instance of the specified element from this queue,
|
jaroslav@633
|
351 |
* if it is present. More formally, removes an element {@code e} such
|
jaroslav@633
|
352 |
* that {@code o.equals(e)}, if this queue contains one or more such
|
jaroslav@633
|
353 |
* elements. Returns {@code true} if and only if this queue contained
|
jaroslav@633
|
354 |
* the specified element (or equivalently, if this queue changed as a
|
jaroslav@633
|
355 |
* result of the call).
|
jaroslav@633
|
356 |
*
|
jaroslav@633
|
357 |
* @param o element to be removed from this queue, if present
|
jaroslav@633
|
358 |
* @return {@code true} if this queue changed as a result of the call
|
jaroslav@633
|
359 |
*/
|
jaroslav@633
|
360 |
public boolean remove(Object o) {
|
jaroslav@633
|
361 |
int i = indexOf(o);
|
jaroslav@633
|
362 |
if (i == -1)
|
jaroslav@633
|
363 |
return false;
|
jaroslav@633
|
364 |
else {
|
jaroslav@633
|
365 |
removeAt(i);
|
jaroslav@633
|
366 |
return true;
|
jaroslav@633
|
367 |
}
|
jaroslav@633
|
368 |
}
|
jaroslav@633
|
369 |
|
jaroslav@633
|
370 |
/**
|
jaroslav@633
|
371 |
* Version of remove using reference equality, not equals.
|
jaroslav@633
|
372 |
* Needed by iterator.remove.
|
jaroslav@633
|
373 |
*
|
jaroslav@633
|
374 |
* @param o element to be removed from this queue, if present
|
jaroslav@633
|
375 |
* @return {@code true} if removed
|
jaroslav@633
|
376 |
*/
|
jaroslav@633
|
377 |
boolean removeEq(Object o) {
|
jaroslav@633
|
378 |
for (int i = 0; i < size; i++) {
|
jaroslav@633
|
379 |
if (o == queue[i]) {
|
jaroslav@633
|
380 |
removeAt(i);
|
jaroslav@633
|
381 |
return true;
|
jaroslav@633
|
382 |
}
|
jaroslav@633
|
383 |
}
|
jaroslav@633
|
384 |
return false;
|
jaroslav@633
|
385 |
}
|
jaroslav@633
|
386 |
|
jaroslav@633
|
387 |
/**
|
jaroslav@633
|
388 |
* Returns {@code true} if this queue contains the specified element.
|
jaroslav@633
|
389 |
* More formally, returns {@code true} if and only if this queue contains
|
jaroslav@633
|
390 |
* at least one element {@code e} such that {@code o.equals(e)}.
|
jaroslav@633
|
391 |
*
|
jaroslav@633
|
392 |
* @param o object to be checked for containment in this queue
|
jaroslav@633
|
393 |
* @return {@code true} if this queue contains the specified element
|
jaroslav@633
|
394 |
*/
|
jaroslav@633
|
395 |
public boolean contains(Object o) {
|
jaroslav@633
|
396 |
return indexOf(o) != -1;
|
jaroslav@633
|
397 |
}
|
jaroslav@633
|
398 |
|
jaroslav@633
|
399 |
/**
|
jaroslav@633
|
400 |
* Returns an array containing all of the elements in this queue.
|
jaroslav@633
|
401 |
* The elements are in no particular order.
|
jaroslav@633
|
402 |
*
|
jaroslav@633
|
403 |
* <p>The returned array will be "safe" in that no references to it are
|
jaroslav@633
|
404 |
* maintained by this queue. (In other words, this method must allocate
|
jaroslav@633
|
405 |
* a new array). The caller is thus free to modify the returned array.
|
jaroslav@633
|
406 |
*
|
jaroslav@633
|
407 |
* <p>This method acts as bridge between array-based and collection-based
|
jaroslav@633
|
408 |
* APIs.
|
jaroslav@633
|
409 |
*
|
jaroslav@633
|
410 |
* @return an array containing all of the elements in this queue
|
jaroslav@633
|
411 |
*/
|
jaroslav@633
|
412 |
public Object[] toArray() {
|
jaroslav@633
|
413 |
return Arrays.copyOf(queue, size);
|
jaroslav@633
|
414 |
}
|
jaroslav@633
|
415 |
|
jaroslav@633
|
416 |
/**
|
jaroslav@633
|
417 |
* Returns an array containing all of the elements in this queue; the
|
jaroslav@633
|
418 |
* runtime type of the returned array is that of the specified array.
|
jaroslav@633
|
419 |
* The returned array elements are in no particular order.
|
jaroslav@633
|
420 |
* If the queue fits in the specified array, it is returned therein.
|
jaroslav@633
|
421 |
* Otherwise, a new array is allocated with the runtime type of the
|
jaroslav@633
|
422 |
* specified array and the size of this queue.
|
jaroslav@633
|
423 |
*
|
jaroslav@633
|
424 |
* <p>If the queue fits in the specified array with room to spare
|
jaroslav@633
|
425 |
* (i.e., the array has more elements than the queue), the element in
|
jaroslav@633
|
426 |
* the array immediately following the end of the collection is set to
|
jaroslav@633
|
427 |
* {@code null}.
|
jaroslav@633
|
428 |
*
|
jaroslav@633
|
429 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between
|
jaroslav@633
|
430 |
* array-based and collection-based APIs. Further, this method allows
|
jaroslav@633
|
431 |
* precise control over the runtime type of the output array, and may,
|
jaroslav@633
|
432 |
* under certain circumstances, be used to save allocation costs.
|
jaroslav@633
|
433 |
*
|
jaroslav@633
|
434 |
* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
|
jaroslav@633
|
435 |
* The following code can be used to dump the queue into a newly
|
jaroslav@633
|
436 |
* allocated array of <tt>String</tt>:
|
jaroslav@633
|
437 |
*
|
jaroslav@633
|
438 |
* <pre>
|
jaroslav@633
|
439 |
* String[] y = x.toArray(new String[0]);</pre>
|
jaroslav@633
|
440 |
*
|
jaroslav@633
|
441 |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to
|
jaroslav@633
|
442 |
* <tt>toArray()</tt>.
|
jaroslav@633
|
443 |
*
|
jaroslav@633
|
444 |
* @param a the array into which the elements of the queue are to
|
jaroslav@633
|
445 |
* be stored, if it is big enough; otherwise, a new array of the
|
jaroslav@633
|
446 |
* same runtime type is allocated for this purpose.
|
jaroslav@633
|
447 |
* @return an array containing all of the elements in this queue
|
jaroslav@633
|
448 |
* @throws ArrayStoreException if the runtime type of the specified array
|
jaroslav@633
|
449 |
* is not a supertype of the runtime type of every element in
|
jaroslav@633
|
450 |
* this queue
|
jaroslav@633
|
451 |
* @throws NullPointerException if the specified array is null
|
jaroslav@633
|
452 |
*/
|
jaroslav@633
|
453 |
public <T> T[] toArray(T[] a) {
|
jaroslav@633
|
454 |
if (a.length < size)
|
jaroslav@633
|
455 |
// Make a new array of a's runtime type, but my contents:
|
jaroslav@633
|
456 |
return (T[]) Arrays.copyOf(queue, size, a.getClass());
|
jaroslav@633
|
457 |
System.arraycopy(queue, 0, a, 0, size);
|
jaroslav@633
|
458 |
if (a.length > size)
|
jaroslav@633
|
459 |
a[size] = null;
|
jaroslav@633
|
460 |
return a;
|
jaroslav@633
|
461 |
}
|
jaroslav@633
|
462 |
|
jaroslav@633
|
463 |
/**
|
jaroslav@633
|
464 |
* Returns an iterator over the elements in this queue. The iterator
|
jaroslav@633
|
465 |
* does not return the elements in any particular order.
|
jaroslav@633
|
466 |
*
|
jaroslav@633
|
467 |
* @return an iterator over the elements in this queue
|
jaroslav@633
|
468 |
*/
|
jaroslav@633
|
469 |
public Iterator<E> iterator() {
|
jaroslav@633
|
470 |
return new Itr();
|
jaroslav@633
|
471 |
}
|
jaroslav@633
|
472 |
|
jaroslav@633
|
473 |
private final class Itr implements Iterator<E> {
|
jaroslav@633
|
474 |
/**
|
jaroslav@633
|
475 |
* Index (into queue array) of element to be returned by
|
jaroslav@633
|
476 |
* subsequent call to next.
|
jaroslav@633
|
477 |
*/
|
jaroslav@633
|
478 |
private int cursor = 0;
|
jaroslav@633
|
479 |
|
jaroslav@633
|
480 |
/**
|
jaroslav@633
|
481 |
* Index of element returned by most recent call to next,
|
jaroslav@633
|
482 |
* unless that element came from the forgetMeNot list.
|
jaroslav@633
|
483 |
* Set to -1 if element is deleted by a call to remove.
|
jaroslav@633
|
484 |
*/
|
jaroslav@633
|
485 |
private int lastRet = -1;
|
jaroslav@633
|
486 |
|
jaroslav@633
|
487 |
/**
|
jaroslav@633
|
488 |
* A queue of elements that were moved from the unvisited portion of
|
jaroslav@633
|
489 |
* the heap into the visited portion as a result of "unlucky" element
|
jaroslav@633
|
490 |
* removals during the iteration. (Unlucky element removals are those
|
jaroslav@633
|
491 |
* that require a siftup instead of a siftdown.) We must visit all of
|
jaroslav@633
|
492 |
* the elements in this list to complete the iteration. We do this
|
jaroslav@633
|
493 |
* after we've completed the "normal" iteration.
|
jaroslav@633
|
494 |
*
|
jaroslav@633
|
495 |
* We expect that most iterations, even those involving removals,
|
jaroslav@633
|
496 |
* will not need to store elements in this field.
|
jaroslav@633
|
497 |
*/
|
jaroslav@633
|
498 |
private ArrayDeque<E> forgetMeNot = null;
|
jaroslav@633
|
499 |
|
jaroslav@633
|
500 |
/**
|
jaroslav@633
|
501 |
* Element returned by the most recent call to next iff that
|
jaroslav@633
|
502 |
* element was drawn from the forgetMeNot list.
|
jaroslav@633
|
503 |
*/
|
jaroslav@633
|
504 |
private E lastRetElt = null;
|
jaroslav@633
|
505 |
|
jaroslav@633
|
506 |
/**
|
jaroslav@633
|
507 |
* The modCount value that the iterator believes that the backing
|
jaroslav@633
|
508 |
* Queue should have. If this expectation is violated, the iterator
|
jaroslav@633
|
509 |
* has detected concurrent modification.
|
jaroslav@633
|
510 |
*/
|
jaroslav@633
|
511 |
private int expectedModCount = modCount;
|
jaroslav@633
|
512 |
|
jaroslav@633
|
513 |
public boolean hasNext() {
|
jaroslav@633
|
514 |
return cursor < size ||
|
jaroslav@633
|
515 |
(forgetMeNot != null && !forgetMeNot.isEmpty());
|
jaroslav@633
|
516 |
}
|
jaroslav@633
|
517 |
|
jaroslav@633
|
518 |
public E next() {
|
jaroslav@633
|
519 |
if (expectedModCount != modCount)
|
jaroslav@633
|
520 |
throw new ConcurrentModificationException();
|
jaroslav@633
|
521 |
if (cursor < size)
|
jaroslav@633
|
522 |
return (E) queue[lastRet = cursor++];
|
jaroslav@633
|
523 |
if (forgetMeNot != null) {
|
jaroslav@633
|
524 |
lastRet = -1;
|
jaroslav@633
|
525 |
lastRetElt = forgetMeNot.poll();
|
jaroslav@633
|
526 |
if (lastRetElt != null)
|
jaroslav@633
|
527 |
return lastRetElt;
|
jaroslav@633
|
528 |
}
|
jaroslav@633
|
529 |
throw new NoSuchElementException();
|
jaroslav@633
|
530 |
}
|
jaroslav@633
|
531 |
|
jaroslav@633
|
532 |
public void remove() {
|
jaroslav@633
|
533 |
if (expectedModCount != modCount)
|
jaroslav@633
|
534 |
throw new ConcurrentModificationException();
|
jaroslav@633
|
535 |
if (lastRet != -1) {
|
jaroslav@633
|
536 |
E moved = PriorityQueue.this.removeAt(lastRet);
|
jaroslav@633
|
537 |
lastRet = -1;
|
jaroslav@633
|
538 |
if (moved == null)
|
jaroslav@633
|
539 |
cursor--;
|
jaroslav@633
|
540 |
else {
|
jaroslav@633
|
541 |
if (forgetMeNot == null)
|
jaroslav@633
|
542 |
forgetMeNot = new ArrayDeque<>();
|
jaroslav@633
|
543 |
forgetMeNot.add(moved);
|
jaroslav@633
|
544 |
}
|
jaroslav@633
|
545 |
} else if (lastRetElt != null) {
|
jaroslav@633
|
546 |
PriorityQueue.this.removeEq(lastRetElt);
|
jaroslav@633
|
547 |
lastRetElt = null;
|
jaroslav@633
|
548 |
} else {
|
jaroslav@633
|
549 |
throw new IllegalStateException();
|
jaroslav@633
|
550 |
}
|
jaroslav@633
|
551 |
expectedModCount = modCount;
|
jaroslav@633
|
552 |
}
|
jaroslav@633
|
553 |
}
|
jaroslav@633
|
554 |
|
jaroslav@633
|
555 |
public int size() {
|
jaroslav@633
|
556 |
return size;
|
jaroslav@633
|
557 |
}
|
jaroslav@633
|
558 |
|
jaroslav@633
|
559 |
/**
|
jaroslav@633
|
560 |
* Removes all of the elements from this priority queue.
|
jaroslav@633
|
561 |
* The queue will be empty after this call returns.
|
jaroslav@633
|
562 |
*/
|
jaroslav@633
|
563 |
public void clear() {
|
jaroslav@633
|
564 |
modCount++;
|
jaroslav@633
|
565 |
for (int i = 0; i < size; i++)
|
jaroslav@633
|
566 |
queue[i] = null;
|
jaroslav@633
|
567 |
size = 0;
|
jaroslav@633
|
568 |
}
|
jaroslav@633
|
569 |
|
jaroslav@633
|
570 |
public E poll() {
|
jaroslav@633
|
571 |
if (size == 0)
|
jaroslav@633
|
572 |
return null;
|
jaroslav@633
|
573 |
int s = --size;
|
jaroslav@633
|
574 |
modCount++;
|
jaroslav@633
|
575 |
E result = (E) queue[0];
|
jaroslav@633
|
576 |
E x = (E) queue[s];
|
jaroslav@633
|
577 |
queue[s] = null;
|
jaroslav@633
|
578 |
if (s != 0)
|
jaroslav@633
|
579 |
siftDown(0, x);
|
jaroslav@633
|
580 |
return result;
|
jaroslav@633
|
581 |
}
|
jaroslav@633
|
582 |
|
jaroslav@633
|
583 |
/**
|
jaroslav@633
|
584 |
* Removes the ith element from queue.
|
jaroslav@633
|
585 |
*
|
jaroslav@633
|
586 |
* Normally this method leaves the elements at up to i-1,
|
jaroslav@633
|
587 |
* inclusive, untouched. Under these circumstances, it returns
|
jaroslav@633
|
588 |
* null. Occasionally, in order to maintain the heap invariant,
|
jaroslav@633
|
589 |
* it must swap a later element of the list with one earlier than
|
jaroslav@633
|
590 |
* i. Under these circumstances, this method returns the element
|
jaroslav@633
|
591 |
* that was previously at the end of the list and is now at some
|
jaroslav@633
|
592 |
* position before i. This fact is used by iterator.remove so as to
|
jaroslav@633
|
593 |
* avoid missing traversing elements.
|
jaroslav@633
|
594 |
*/
|
jaroslav@633
|
595 |
private E removeAt(int i) {
|
jaroslav@633
|
596 |
assert i >= 0 && i < size;
|
jaroslav@633
|
597 |
modCount++;
|
jaroslav@633
|
598 |
int s = --size;
|
jaroslav@633
|
599 |
if (s == i) // removed last element
|
jaroslav@633
|
600 |
queue[i] = null;
|
jaroslav@633
|
601 |
else {
|
jaroslav@633
|
602 |
E moved = (E) queue[s];
|
jaroslav@633
|
603 |
queue[s] = null;
|
jaroslav@633
|
604 |
siftDown(i, moved);
|
jaroslav@633
|
605 |
if (queue[i] == moved) {
|
jaroslav@633
|
606 |
siftUp(i, moved);
|
jaroslav@633
|
607 |
if (queue[i] != moved)
|
jaroslav@633
|
608 |
return moved;
|
jaroslav@633
|
609 |
}
|
jaroslav@633
|
610 |
}
|
jaroslav@633
|
611 |
return null;
|
jaroslav@633
|
612 |
}
|
jaroslav@633
|
613 |
|
jaroslav@633
|
614 |
/**
|
jaroslav@633
|
615 |
* Inserts item x at position k, maintaining heap invariant by
|
jaroslav@633
|
616 |
* promoting x up the tree until it is greater than or equal to
|
jaroslav@633
|
617 |
* its parent, or is the root.
|
jaroslav@633
|
618 |
*
|
jaroslav@633
|
619 |
* To simplify and speed up coercions and comparisons. the
|
jaroslav@633
|
620 |
* Comparable and Comparator versions are separated into different
|
jaroslav@633
|
621 |
* methods that are otherwise identical. (Similarly for siftDown.)
|
jaroslav@633
|
622 |
*
|
jaroslav@633
|
623 |
* @param k the position to fill
|
jaroslav@633
|
624 |
* @param x the item to insert
|
jaroslav@633
|
625 |
*/
|
jaroslav@633
|
626 |
private void siftUp(int k, E x) {
|
jaroslav@633
|
627 |
if (comparator != null)
|
jaroslav@633
|
628 |
siftUpUsingComparator(k, x);
|
jaroslav@633
|
629 |
else
|
jaroslav@633
|
630 |
siftUpComparable(k, x);
|
jaroslav@633
|
631 |
}
|
jaroslav@633
|
632 |
|
jaroslav@633
|
633 |
private void siftUpComparable(int k, E x) {
|
jaroslav@633
|
634 |
Comparable<? super E> key = (Comparable<? super E>) x;
|
jaroslav@633
|
635 |
while (k > 0) {
|
jaroslav@633
|
636 |
int parent = (k - 1) >>> 1;
|
jaroslav@633
|
637 |
Object e = queue[parent];
|
jaroslav@633
|
638 |
if (key.compareTo((E) e) >= 0)
|
jaroslav@633
|
639 |
break;
|
jaroslav@633
|
640 |
queue[k] = e;
|
jaroslav@633
|
641 |
k = parent;
|
jaroslav@633
|
642 |
}
|
jaroslav@633
|
643 |
queue[k] = key;
|
jaroslav@633
|
644 |
}
|
jaroslav@633
|
645 |
|
jaroslav@633
|
646 |
private void siftUpUsingComparator(int k, E x) {
|
jaroslav@633
|
647 |
while (k > 0) {
|
jaroslav@633
|
648 |
int parent = (k - 1) >>> 1;
|
jaroslav@633
|
649 |
Object e = queue[parent];
|
jaroslav@633
|
650 |
if (comparator.compare(x, (E) e) >= 0)
|
jaroslav@633
|
651 |
break;
|
jaroslav@633
|
652 |
queue[k] = e;
|
jaroslav@633
|
653 |
k = parent;
|
jaroslav@633
|
654 |
}
|
jaroslav@633
|
655 |
queue[k] = x;
|
jaroslav@633
|
656 |
}
|
jaroslav@633
|
657 |
|
jaroslav@633
|
658 |
/**
|
jaroslav@633
|
659 |
* Inserts item x at position k, maintaining heap invariant by
|
jaroslav@633
|
660 |
* demoting x down the tree repeatedly until it is less than or
|
jaroslav@633
|
661 |
* equal to its children or is a leaf.
|
jaroslav@633
|
662 |
*
|
jaroslav@633
|
663 |
* @param k the position to fill
|
jaroslav@633
|
664 |
* @param x the item to insert
|
jaroslav@633
|
665 |
*/
|
jaroslav@633
|
666 |
private void siftDown(int k, E x) {
|
jaroslav@633
|
667 |
if (comparator != null)
|
jaroslav@633
|
668 |
siftDownUsingComparator(k, x);
|
jaroslav@633
|
669 |
else
|
jaroslav@633
|
670 |
siftDownComparable(k, x);
|
jaroslav@633
|
671 |
}
|
jaroslav@633
|
672 |
|
jaroslav@633
|
673 |
private void siftDownComparable(int k, E x) {
|
jaroslav@633
|
674 |
Comparable<? super E> key = (Comparable<? super E>)x;
|
jaroslav@633
|
675 |
int half = size >>> 1; // loop while a non-leaf
|
jaroslav@633
|
676 |
while (k < half) {
|
jaroslav@633
|
677 |
int child = (k << 1) + 1; // assume left child is least
|
jaroslav@633
|
678 |
Object c = queue[child];
|
jaroslav@633
|
679 |
int right = child + 1;
|
jaroslav@633
|
680 |
if (right < size &&
|
jaroslav@633
|
681 |
((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
|
jaroslav@633
|
682 |
c = queue[child = right];
|
jaroslav@633
|
683 |
if (key.compareTo((E) c) <= 0)
|
jaroslav@633
|
684 |
break;
|
jaroslav@633
|
685 |
queue[k] = c;
|
jaroslav@633
|
686 |
k = child;
|
jaroslav@633
|
687 |
}
|
jaroslav@633
|
688 |
queue[k] = key;
|
jaroslav@633
|
689 |
}
|
jaroslav@633
|
690 |
|
jaroslav@633
|
691 |
private void siftDownUsingComparator(int k, E x) {
|
jaroslav@633
|
692 |
int half = size >>> 1;
|
jaroslav@633
|
693 |
while (k < half) {
|
jaroslav@633
|
694 |
int child = (k << 1) + 1;
|
jaroslav@633
|
695 |
Object c = queue[child];
|
jaroslav@633
|
696 |
int right = child + 1;
|
jaroslav@633
|
697 |
if (right < size &&
|
jaroslav@633
|
698 |
comparator.compare((E) c, (E) queue[right]) > 0)
|
jaroslav@633
|
699 |
c = queue[child = right];
|
jaroslav@633
|
700 |
if (comparator.compare(x, (E) c) <= 0)
|
jaroslav@633
|
701 |
break;
|
jaroslav@633
|
702 |
queue[k] = c;
|
jaroslav@633
|
703 |
k = child;
|
jaroslav@633
|
704 |
}
|
jaroslav@633
|
705 |
queue[k] = x;
|
jaroslav@633
|
706 |
}
|
jaroslav@633
|
707 |
|
jaroslav@633
|
708 |
/**
|
jaroslav@633
|
709 |
* Establishes the heap invariant (described above) in the entire tree,
|
jaroslav@633
|
710 |
* assuming nothing about the order of the elements prior to the call.
|
jaroslav@633
|
711 |
*/
|
jaroslav@633
|
712 |
private void heapify() {
|
jaroslav@633
|
713 |
for (int i = (size >>> 1) - 1; i >= 0; i--)
|
jaroslav@633
|
714 |
siftDown(i, (E) queue[i]);
|
jaroslav@633
|
715 |
}
|
jaroslav@633
|
716 |
|
jaroslav@633
|
717 |
/**
|
jaroslav@633
|
718 |
* Returns the comparator used to order the elements in this
|
jaroslav@633
|
719 |
* queue, or {@code null} if this queue is sorted according to
|
jaroslav@633
|
720 |
* the {@linkplain Comparable natural ordering} of its elements.
|
jaroslav@633
|
721 |
*
|
jaroslav@633
|
722 |
* @return the comparator used to order this queue, or
|
jaroslav@633
|
723 |
* {@code null} if this queue is sorted according to the
|
jaroslav@633
|
724 |
* natural ordering of its elements
|
jaroslav@633
|
725 |
*/
|
jaroslav@633
|
726 |
public Comparator<? super E> comparator() {
|
jaroslav@633
|
727 |
return comparator;
|
jaroslav@633
|
728 |
}
|
jaroslav@633
|
729 |
|
jaroslav@633
|
730 |
|
jaroslav@633
|
731 |
}
|