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package java.util; |
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/* |
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* %W% %E% |
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* |
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* Copyright 2003 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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|
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package java.util; |
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/** |
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* An unbounded priority queue based on a priority heap. This queue orders |
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* elements according to an order specified at construction time, which is |
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* specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered |
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* either according to their <i>natural order</i> (see {@link Comparable}), or |
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* according to a {@link Comparator}, depending on which constructor is used. |
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* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the |
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* minimal element with respect to the specified ordering. If multiple |
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* elements are tied for least value, no guarantees are made as to |
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* which of these elements is returned. |
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* An unbounded priority {@linkplain Queue queue} based on a priority |
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* heap. This queue orders elements according to an order specified |
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* at construction time, which is specified either according to their |
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* <i>natural order</i> (see {@link Comparable}), or according to a |
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* {@link java.util.Comparator}, depending on which constructor is |
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* used. A priority queue does not permit <tt>null</tt> elements. |
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* A priority queue relying on natural ordering also does not |
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* permit insertion of non-comparable objects (doing so may result |
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* in <tt>ClassCastException</tt>). |
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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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* element at the head of the queue. |
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* |
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* <p>A priority queue has a <i>capacity</i>. The capacity is the |
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* size of the array used internally to store the elements on the |
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* queue. It is always at least as large as the queue size. As |
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* elements are added to a priority queue, its capacity grows |
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* automatically. The details of the growth policy are not specified. |
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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>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>This class implements all of the <em>optional</em> methods of |
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* the {@link Collection} and {@link Iterator} interfaces. The |
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* Iterator provided in method {@link #iterator()} is <em>not</em> |
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* guaranteed to traverse the elements of the PriorityQueue in any |
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* particular order. If you need ordered traversal, consider using |
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* <tt>Arrays.sort(pq.toArray())</tt>. |
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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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* java.util.concurrent.PriorityBlockingQueue} class. |
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* |
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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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* |
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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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* Java Collections Framework</a>. |
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* @since 1.5 |
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* @version %I%, %G% |
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* @author Josh Bloch |
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* @param <E> the base class of all 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 Queue<E>, |
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java.io.Serializable { |
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implements Queue<E>, java.io.Serializable { |
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|
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private static final long serialVersionUID = -7720805057305804111L; |
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|
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private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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/** |
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* |
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* queue.length must be >= 2, even if size == 0. |
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*/ |
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private transient E[] queue; |
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private transient Object[] queue; |
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|
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/** |
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* The number of elements in the priority queue. |
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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<E> comparator; |
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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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private transient int modCount = 0; |
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/** |
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* Create a new priority queue with the default initial capacity |
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* Creates a <tt>PriorityQueue</tt> with the default initial capacity |
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* (11) that orders its elements according to their natural |
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* ordering (using <tt>Comparable</tt>.) |
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* ordering (using <tt>Comparable</tt>). |
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*/ |
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public PriorityQueue() { |
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this(DEFAULT_INITIAL_CAPACITY); |
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this(DEFAULT_INITIAL_CAPACITY, null); |
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} |
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/** |
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* Create a new priority queue with the specified initial capacity |
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* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
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* that orders its elements according to their natural ordering |
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* (using <tt>Comparable</tt>.) |
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* (using <tt>Comparable</tt>). |
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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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*/ |
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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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* Create a new priority queue with the specified initial capacity (11) |
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* Creates a <tt>PriorityQueue</tt> 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 used to order this priority queue. |
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* If <tt>null</tt> then the order depends on the elements' natural |
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* ordering. |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
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* than 1 |
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*/ |
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public PriorityQueue(int initialCapacity, Comparator<E> comparator) { |
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public PriorityQueue(int initialCapacity, |
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Comparator<? super E> comparator) { |
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if (initialCapacity < 1) |
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initialCapacity = 1; |
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queue = new E[initialCapacity + 1]; |
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throw new IllegalArgumentException(); |
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this.queue = new Object[initialCapacity + 1]; |
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this.comparator = comparator; |
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} |
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|
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/** |
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* Create a new priority queue containing the elements in the specified |
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* collection. The priority queue has an initial capacity of 110% of the |
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* size of the specified collection. If the specified collection |
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* implements the {@link Sorted} interface, the priority queue will be |
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* sorted according to the same comparator, or according to its elements' |
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* natural order if the collection is sorted according to its elements' |
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* natural order. If the specified collection does not implement |
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* <tt>Sorted</tt>, the priority queue is ordered according to |
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* its elements' natural order. |
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* |
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* @param initialElements 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 an |
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* element of the specified collection is <tt>null</tt>. |
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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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public PriorityQueue(Collection<E> initialElements) { |
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int sz = initialElements.size(); |
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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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queue = new E[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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queue[++size] = i.next(); |
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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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queue[++size] = i.next(); |
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heapify(); |
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} |
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|
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if (initialElements instanceof Sorted) { |
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comparator = ((Sorted)initialElements).comparator(); |
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for (Iterator<E> i = initialElements.iterator(); i.hasNext(); ) |
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queue[++size] = i.next(); |
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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 sorted |
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* according to the same comparator, or according to its elements' |
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* natural order if the collection is sorted according to its |
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* elements' natural order. Otherwise, the priority queue is |
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* ordered according to its elements' natural order. |
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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 <tt>c</tt> or any element within it |
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* is <tt>null</tt> |
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*/ |
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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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// @fixme double-cast workaround for compiler |
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SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)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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< |
for (Iterator<E> i = initialElements.iterator(); i.hasNext(); ) |
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add(i.next()); |
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> |
fillFromUnsorted(c); |
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} |
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} |
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|
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< |
// Queue Methods |
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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. This priority queue will be sorted |
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> |
* according to the same comparator as the given collection, or |
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> |
* according to its elements' natural order if the collection is |
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> |
* sorted according to its elements' natural order. |
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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 <tt>c</tt> or any element within it |
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> |
* is <tt>null</tt> |
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*/ |
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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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> |
} |
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|
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/** |
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< |
* Remove and return the minimal element from this priority queue |
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< |
* if it contains one or more elements, otherwise return |
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< |
* <tt>null</tt>. The term <i>minimal</i> is defined according to |
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< |
* this priority queue's order. |
| 240 |
> |
* 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. This priority queue will be sorted |
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> |
* according to the same comparator as the given collection, or |
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> |
* according to its elements' natural order if the collection is |
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> |
* sorted according to its elements' natural order. |
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|
* |
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< |
* @return the minimal element from this priority queue if it contains |
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< |
* one or more elements, otherwise <tt>null</tt>. |
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> |
* @param c the collection whose elements are to be placed |
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> |
* into this priority queue. |
| 250 |
> |
* @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 <tt>c</tt> or any element within it |
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> |
* is <tt>null</tt> |
| 255 |
|
*/ |
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< |
public E poll() { |
| 257 |
< |
if (size == 0) |
| 258 |
< |
return null; |
| 259 |
< |
return remove(1); |
| 256 |
> |
public PriorityQueue(SortedSet<? extends E> c) { |
| 257 |
> |
initializeArray(c); |
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> |
comparator = (Comparator<? super E>)c.comparator(); |
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> |
fillFromSorted(c); |
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|
} |
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|
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|
/** |
| 263 |
< |
* Return, but do not remove, the minimal element from the |
| 264 |
< |
* priority queue, or return <tt>null</tt> if the queue is empty. |
| 265 |
< |
* The term <i>minimal</i> is defined according to this priority |
| 266 |
< |
* queue's order. This method returns the same object reference |
| 267 |
< |
* that would be returned by by the <tt>poll</tt> method. The two |
| 268 |
< |
* methods differ in that this method does not remove the element |
| 269 |
< |
* from the priority queue. |
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> |
* Resize array, if necessary, to be able to hold given index |
| 264 |
> |
*/ |
| 265 |
> |
private void grow(int index) { |
| 266 |
> |
int newlen = queue.length; |
| 267 |
> |
if (index < newlen) // don't need to grow |
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> |
return; |
| 269 |
> |
if (index == Integer.MAX_VALUE) |
| 270 |
> |
throw new OutOfMemoryError(); |
| 271 |
> |
while (newlen <= index) { |
| 272 |
> |
if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow |
| 273 |
> |
newlen = Integer.MAX_VALUE; |
| 274 |
> |
else |
| 275 |
> |
newlen <<= 2; |
| 276 |
> |
} |
| 277 |
> |
Object[] newQueue = new Object[newlen]; |
| 278 |
> |
System.arraycopy(queue, 0, newQueue, 0, queue.length); |
| 279 |
> |
queue = newQueue; |
| 280 |
> |
} |
| 281 |
> |
|
| 282 |
> |
|
| 283 |
> |
/** |
| 284 |
> |
* Inserts the specified element into this priority queue. |
| 285 |
|
* |
| 286 |
< |
* @return the minimal element from this priority queue if it contains |
| 287 |
< |
* one or more elements, otherwise <tt>null</tt>. |
| 286 |
> |
* @return <tt>true</tt> |
| 287 |
> |
* @throws ClassCastException if the specified element cannot be compared |
| 288 |
> |
* with elements currently in the priority queue according |
| 289 |
> |
* to the priority queue's ordering. |
| 290 |
> |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
| 291 |
|
*/ |
| 292 |
+ |
public boolean offer(E o) { |
| 293 |
+ |
if (o == null) |
| 294 |
+ |
throw new NullPointerException(); |
| 295 |
+ |
modCount++; |
| 296 |
+ |
++size; |
| 297 |
+ |
|
| 298 |
+ |
// Grow backing store if necessary |
| 299 |
+ |
if (size >= queue.length) |
| 300 |
+ |
grow(size); |
| 301 |
+ |
|
| 302 |
+ |
queue[size] = o; |
| 303 |
+ |
fixUp(size); |
| 304 |
+ |
return true; |
| 305 |
+ |
} |
| 306 |
+ |
|
| 307 |
|
public E peek() { |
| 308 |
< |
return queue[1]; |
| 308 |
> |
if (size == 0) |
| 309 |
> |
return null; |
| 310 |
> |
return (E) queue[1]; |
| 311 |
|
} |
| 312 |
|
|
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< |
// Collection Methods |
| 313 |
> |
// Collection Methods - the first two override to update docs |
| 314 |
|
|
| 315 |
|
/** |
| 316 |
< |
* Removes a single instance of the specified element from this priority |
| 317 |
< |
* queue, if it is present. Returns true if this collection contained the |
| 318 |
< |
* specified element (or equivalently, if this collection changed as a |
| 182 |
< |
* result of the call). |
| 316 |
> |
* Adds the specified element to this queue. |
| 317 |
> |
* @return <tt>true</tt> (as per the general contract of |
| 318 |
> |
* <tt>Collection.add</tt>). |
| 319 |
|
* |
| 320 |
< |
* @param element the element to be removed from this collection, |
| 185 |
< |
* if present. |
| 186 |
< |
* @return <tt>true</tt> if this collection changed as a result of the |
| 187 |
< |
* call |
| 320 |
> |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
| 321 |
|
* @throws ClassCastException if the specified element cannot be compared |
| 322 |
< |
* with elements currently in the priority queue according |
| 323 |
< |
* to the priority queue's ordering. |
| 191 |
< |
* @throws NullPointerException if the specified element is null. |
| 322 |
> |
* with elements currently in the priority queue according |
| 323 |
> |
* to the priority queue's ordering. |
| 324 |
|
*/ |
| 325 |
< |
public boolean remove(Object element) { |
| 326 |
< |
if (element == null) |
| 327 |
< |
throw new NullPointerException(); |
| 325 |
> |
public boolean add(E o) { |
| 326 |
> |
return offer(o); |
| 327 |
> |
} |
| 328 |
> |
|
| 329 |
> |
public boolean remove(Object o) { |
| 330 |
> |
if (o == null) |
| 331 |
> |
return false; |
| 332 |
|
|
| 333 |
|
if (comparator == null) { |
| 334 |
|
for (int i = 1; i <= size; i++) { |
| 335 |
< |
if (((Comparable)queue[i]).compareTo(element) == 0) { |
| 336 |
< |
remove(i); |
| 335 |
> |
if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) { |
| 336 |
> |
removeAt(i); |
| 337 |
|
return true; |
| 338 |
|
} |
| 339 |
|
} |
| 340 |
|
} else { |
| 341 |
|
for (int i = 1; i <= size; i++) { |
| 342 |
< |
if (comparator.compare(queue[i], (E) element) == 0) { |
| 343 |
< |
remove(i); |
| 342 |
> |
if (comparator.compare((E)queue[i], (E)o) == 0) { |
| 343 |
> |
removeAt(i); |
| 344 |
|
return true; |
| 345 |
|
} |
| 346 |
|
} |
| 349 |
|
} |
| 350 |
|
|
| 351 |
|
/** |
| 352 |
< |
* Returns an iterator over the elements in this priority queue. The |
| 353 |
< |
* elements of the priority queue will be returned by this iterator in the |
| 354 |
< |
* order specified by the queue, which is to say the order they would be |
| 355 |
< |
* returned by repeated calls to <tt>poll</tt>. |
| 220 |
< |
* |
| 221 |
< |
* @return an <tt>Iterator</tt> over the elements in this priority queue. |
| 352 |
> |
* Returns an iterator over the elements in this queue. The iterator |
| 353 |
> |
* does not return the elements in any particular order. |
| 354 |
> |
* |
| 355 |
> |
* @return an iterator over the elements in this queue. |
| 356 |
|
*/ |
| 357 |
|
public Iterator<E> iterator() { |
| 358 |
|
return new Itr(); |
| 359 |
|
} |
| 360 |
|
|
| 361 |
|
private class Itr implements Iterator<E> { |
| 362 |
+ |
|
| 363 |
|
/** |
| 364 |
|
* Index (into queue array) of element to be returned by |
| 365 |
|
* subsequent call to next. |
| 367 |
|
private int cursor = 1; |
| 368 |
|
|
| 369 |
|
/** |
| 370 |
< |
* Index of element returned by most recent call to next or |
| 371 |
< |
* previous. Reset to 0 if this element is deleted by a call |
| 372 |
< |
* to remove. |
| 370 |
> |
* Index of element returned by most recent call to next, |
| 371 |
> |
* unless that element came from the forgetMeNot list. |
| 372 |
> |
* Reset to 0 if element is deleted by a call to remove. |
| 373 |
|
*/ |
| 374 |
|
private int lastRet = 0; |
| 375 |
|
|
| 380 |
|
*/ |
| 381 |
|
private int expectedModCount = modCount; |
| 382 |
|
|
| 383 |
+ |
/** |
| 384 |
+ |
* A list of elements that were moved from the unvisited portion of |
| 385 |
+ |
* the heap into the visited portion as a result of "unlucky" element |
| 386 |
+ |
* removals during the iteration. (Unlucky element removals are those |
| 387 |
+ |
* that require a fixup instead of a fixdown.) We must visit all of |
| 388 |
+ |
* the elements in this list to complete the iteration. We do this |
| 389 |
+ |
* after we've completed the "normal" iteration. |
| 390 |
+ |
* |
| 391 |
+ |
* We expect that most iterations, even those involving removals, |
| 392 |
+ |
* will not use need to store elements in this field. |
| 393 |
+ |
*/ |
| 394 |
+ |
private ArrayList<E> forgetMeNot = null; |
| 395 |
+ |
|
| 396 |
+ |
/** |
| 397 |
+ |
* Element returned by the most recent call to next iff that |
| 398 |
+ |
* element was drawn from the forgetMeNot list. |
| 399 |
+ |
*/ |
| 400 |
+ |
private Object lastRetElt = null; |
| 401 |
+ |
|
| 402 |
|
public boolean hasNext() { |
| 403 |
< |
return cursor <= size; |
| 403 |
> |
return cursor <= size || forgetMeNot != null; |
| 404 |
|
} |
| 405 |
|
|
| 406 |
|
public E next() { |
| 407 |
|
checkForComodification(); |
| 408 |
< |
if (cursor > size) |
| 408 |
> |
E result; |
| 409 |
> |
if (cursor <= size) { |
| 410 |
> |
result = (E) queue[cursor]; |
| 411 |
> |
lastRet = cursor++; |
| 412 |
> |
} |
| 413 |
> |
else if (forgetMeNot == null) |
| 414 |
|
throw new NoSuchElementException(); |
| 415 |
< |
E result = queue[cursor]; |
| 416 |
< |
lastRet = cursor++; |
| 415 |
> |
else { |
| 416 |
> |
int remaining = forgetMeNot.size(); |
| 417 |
> |
result = forgetMeNot.remove(remaining - 1); |
| 418 |
> |
if (remaining == 1) |
| 419 |
> |
forgetMeNot = null; |
| 420 |
> |
lastRet = 0; |
| 421 |
> |
lastRetElt = result; |
| 422 |
> |
} |
| 423 |
|
return result; |
| 424 |
|
} |
| 425 |
|
|
| 426 |
|
public void remove() { |
| 262 |
– |
if (lastRet == 0) |
| 263 |
– |
throw new IllegalStateException(); |
| 427 |
|
checkForComodification(); |
| 428 |
|
|
| 429 |
< |
PriorityQueue.this.remove(lastRet); |
| 430 |
< |
if (lastRet < cursor) |
| 431 |
< |
cursor--; |
| 432 |
< |
lastRet = 0; |
| 429 |
> |
if (lastRet != 0) { |
| 430 |
> |
E moved = PriorityQueue.this.removeAt(lastRet); |
| 431 |
> |
lastRet = 0; |
| 432 |
> |
if (moved == null) { |
| 433 |
> |
cursor--; |
| 434 |
> |
} else { |
| 435 |
> |
if (forgetMeNot == null) |
| 436 |
> |
forgetMeNot = new ArrayList<E>(); |
| 437 |
> |
forgetMeNot.add(moved); |
| 438 |
> |
} |
| 439 |
> |
} else if (lastRetElt != null) { |
| 440 |
> |
PriorityQueue.this.remove(lastRetElt); |
| 441 |
> |
lastRetElt = null; |
| 442 |
> |
} else { |
| 443 |
> |
throw new IllegalStateException(); |
| 444 |
> |
} |
| 445 |
> |
|
| 446 |
|
expectedModCount = modCount; |
| 447 |
|
} |
| 448 |
|
|
| 452 |
|
} |
| 453 |
|
} |
| 454 |
|
|
| 279 |
– |
/** |
| 280 |
– |
* Returns the number of elements in this priority queue. |
| 281 |
– |
* |
| 282 |
– |
* @return the number of elements in this priority queue. |
| 283 |
– |
*/ |
| 455 |
|
public int size() { |
| 456 |
|
return size; |
| 457 |
|
} |
| 458 |
|
|
| 459 |
|
/** |
| 289 |
– |
* Add the specified element to this priority queue. |
| 290 |
– |
* |
| 291 |
– |
* @param element the element to add. |
| 292 |
– |
* @return true |
| 293 |
– |
* @throws ClassCastException if the specified element cannot be compared |
| 294 |
– |
* with elements currently in the priority queue according |
| 295 |
– |
* to the priority queue's ordering. |
| 296 |
– |
* @throws NullPointerException if the specified element is null. |
| 297 |
– |
*/ |
| 298 |
– |
public boolean offer(E element) { |
| 299 |
– |
if (element == null) |
| 300 |
– |
throw new NullPointerException(); |
| 301 |
– |
modCount++; |
| 302 |
– |
++size; |
| 303 |
– |
|
| 304 |
– |
// Grow backing store if necessary |
| 305 |
– |
while (size >= queue.length) { |
| 306 |
– |
E[] newQueue = new E[2 * queue.length]; |
| 307 |
– |
System.arraycopy(queue, 0, newQueue, 0, queue.length); |
| 308 |
– |
queue = newQueue; |
| 309 |
– |
} |
| 310 |
– |
|
| 311 |
– |
queue[size] = element; |
| 312 |
– |
fixUp(size); |
| 313 |
– |
return true; |
| 314 |
– |
} |
| 315 |
– |
|
| 316 |
– |
/** |
| 460 |
|
* Remove all elements from the priority queue. |
| 461 |
|
*/ |
| 462 |
|
public void clear() { |
| 469 |
|
size = 0; |
| 470 |
|
} |
| 471 |
|
|
| 472 |
+ |
public E poll() { |
| 473 |
+ |
if (size == 0) |
| 474 |
+ |
return null; |
| 475 |
+ |
modCount++; |
| 476 |
+ |
|
| 477 |
+ |
E result = (E) queue[1]; |
| 478 |
+ |
queue[1] = queue[size]; |
| 479 |
+ |
queue[size--] = null; // Drop extra ref to prevent memory leak |
| 480 |
+ |
if (size > 1) |
| 481 |
+ |
fixDown(1); |
| 482 |
+ |
|
| 483 |
+ |
return result; |
| 484 |
+ |
} |
| 485 |
+ |
|
| 486 |
|
/** |
| 487 |
< |
* Removes and returns the ith element from queue. Recall |
| 488 |
< |
* that queue is one-based, so 1 <= i <= size. |
| 487 |
> |
* Removes and returns the ith element from queue. (Recall that queue |
| 488 |
> |
* is one-based, so 1 <= i <= size.) |
| 489 |
|
* |
| 490 |
< |
* XXX: Could further special-case i==size, but is it worth it? |
| 491 |
< |
* XXX: Could special-case i==0, but is it worth it? |
| 490 |
> |
* Normally this method leaves the elements at positions from 1 up to i-1, |
| 491 |
> |
* inclusive, untouched. Under these circumstances, it returns null. |
| 492 |
> |
* Occasionally, in order to maintain the heap invariant, it must move |
| 493 |
> |
* the last element of the list to some index in the range [2, i-1], |
| 494 |
> |
* and move the element previously at position (i/2) to position i. |
| 495 |
> |
* Under these circumstances, this method returns the element that was |
| 496 |
> |
* previously at the end of the list and is now at some position between |
| 497 |
> |
* 2 and i-1 inclusive. |
| 498 |
|
*/ |
| 499 |
< |
private E remove(int i) { |
| 500 |
< |
assert i <= size; |
| 499 |
> |
private E removeAt(int i) { |
| 500 |
> |
assert i > 0 && i <= size; |
| 501 |
|
modCount++; |
| 502 |
|
|
| 503 |
< |
E result = queue[i]; |
| 504 |
< |
queue[i] = queue[size]; |
| 503 |
> |
E moved = (E) queue[size]; |
| 504 |
> |
queue[i] = moved; |
| 505 |
|
queue[size--] = null; // Drop extra ref to prevent memory leak |
| 506 |
< |
if (i <= size) |
| 506 |
> |
if (i <= size) { |
| 507 |
|
fixDown(i); |
| 508 |
< |
return result; |
| 508 |
> |
if (queue[i] == moved) { |
| 509 |
> |
fixUp(i); |
| 510 |
> |
if (queue[i] != moved) |
| 511 |
> |
return moved; |
| 512 |
> |
} |
| 513 |
> |
} |
| 514 |
> |
return null; |
| 515 |
|
} |
| 516 |
|
|
| 517 |
|
/** |
| 527 |
|
if (comparator == null) { |
| 528 |
|
while (k > 1) { |
| 529 |
|
int j = k >> 1; |
| 530 |
< |
if (((Comparable)queue[j]).compareTo(queue[k]) <= 0) |
| 530 |
> |
if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0) |
| 531 |
|
break; |
| 532 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 532 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 533 |
|
k = j; |
| 534 |
|
} |
| 535 |
|
} else { |
| 536 |
|
while (k > 1) { |
| 537 |
< |
int j = k >> 1; |
| 538 |
< |
if (comparator.compare(queue[j], queue[k]) <= 0) |
| 537 |
> |
int j = k >>> 1; |
| 538 |
> |
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
| 539 |
|
break; |
| 540 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 540 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 541 |
|
k = j; |
| 542 |
|
} |
| 543 |
|
} |
| 555 |
|
private void fixDown(int k) { |
| 556 |
|
int j; |
| 557 |
|
if (comparator == null) { |
| 558 |
< |
while ((j = k << 1) <= size) { |
| 559 |
< |
if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0) |
| 558 |
> |
while ((j = k << 1) <= size && (j > 0)) { |
| 559 |
> |
if (j<size && |
| 560 |
> |
((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
| 561 |
|
j++; // j indexes smallest kid |
| 562 |
< |
if (((Comparable)queue[k]).compareTo(queue[j]) <= 0) |
| 562 |
> |
|
| 563 |
> |
if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
| 564 |
|
break; |
| 565 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 565 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 566 |
|
k = j; |
| 567 |
|
} |
| 568 |
|
} else { |
| 569 |
< |
while ((j = k << 1) <= size) { |
| 570 |
< |
if (j < size && comparator.compare(queue[j], queue[j+1]) > 0) |
| 569 |
> |
while ((j = k << 1) <= size && (j > 0)) { |
| 570 |
> |
if (j<size && |
| 571 |
> |
comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
| 572 |
|
j++; // j indexes smallest kid |
| 573 |
< |
if (comparator.compare(queue[k], queue[j]) <= 0) |
| 573 |
> |
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
| 574 |
|
break; |
| 575 |
< |
E tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 575 |
> |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 576 |
|
k = j; |
| 577 |
|
} |
| 578 |
|
} |
| 579 |
|
} |
| 580 |
|
|
| 581 |
|
/** |
| 582 |
< |
* Returns the comparator associated with this priority queue, or |
| 583 |
< |
* <tt>null</tt> if it uses its elements' natural ordering. |
| 582 |
> |
* Establishes the heap invariant (described above) in the entire tree, |
| 583 |
> |
* assuming nothing about the order of the elements prior to the call. |
| 584 |
> |
*/ |
| 585 |
> |
private void heapify() { |
| 586 |
> |
for (int i = size/2; i >= 1; i--) |
| 587 |
> |
fixDown(i); |
| 588 |
> |
} |
| 589 |
> |
|
| 590 |
> |
/** |
| 591 |
> |
* Returns the comparator used to order this collection, or <tt>null</tt> |
| 592 |
> |
* if this collection is sorted according to its elements natural ordering |
| 593 |
> |
* (using <tt>Comparable</tt>). |
| 594 |
|
* |
| 595 |
< |
* @return the comparator associated with this priority queue, or |
| 596 |
< |
* <tt>null</tt> if it uses its elements' natural ordering. |
| 595 |
> |
* @return the comparator used to order this collection, or <tt>null</tt> |
| 596 |
> |
* if this collection is sorted according to its elements natural ordering. |
| 597 |
|
*/ |
| 598 |
< |
public Comparator comparator() { |
| 598 |
> |
public Comparator<? super E> comparator() { |
| 599 |
|
return comparator; |
| 600 |
|
} |
| 601 |
|
|
| 608 |
|
* <tt>Object</tt>) in the proper order. |
| 609 |
|
* @param s the stream |
| 610 |
|
*/ |
| 611 |
< |
private synchronized void writeObject(java.io.ObjectOutputStream s) |
| 611 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
| 612 |
|
throws java.io.IOException{ |
| 613 |
|
// Write out element count, and any hidden stuff |
| 614 |
|
s.defaultWriteObject(); |
| 617 |
|
s.writeInt(queue.length); |
| 618 |
|
|
| 619 |
|
// Write out all elements in the proper order. |
| 620 |
< |
for (int i=0; i<size; i++) |
| 620 |
> |
for (int i=1; i<=size; i++) |
| 621 |
|
s.writeObject(queue[i]); |
| 622 |
|
} |
| 623 |
|
|
| 626 |
|
* deserialize it). |
| 627 |
|
* @param s the stream |
| 628 |
|
*/ |
| 629 |
< |
private synchronized void readObject(java.io.ObjectInputStream s) |
| 629 |
> |
private void readObject(java.io.ObjectInputStream s) |
| 630 |
|
throws java.io.IOException, ClassNotFoundException { |
| 631 |
|
// Read in size, and any hidden stuff |
| 632 |
|
s.defaultReadObject(); |
| 633 |
|
|
| 634 |
|
// Read in array length and allocate array |
| 635 |
|
int arrayLength = s.readInt(); |
| 636 |
< |
queue = new E[arrayLength]; |
| 636 |
> |
queue = new Object[arrayLength]; |
| 637 |
|
|
| 638 |
|
// Read in all elements in the proper order. |
| 639 |
< |
for (int i=0; i<size; i++) |
| 640 |
< |
queue[i] = (E)s.readObject(); |
| 639 |
> |
for (int i=1; i<=size; i++) |
| 640 |
> |
queue[i] = (E) s.readObject(); |
| 641 |
|
} |
| 642 |
|
|
| 643 |
|
} |
