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/* |
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* @(#)PriorityQueue.java 1.8 05/08/27 |
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* %W% %E% |
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* |
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
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* Copyright 2007 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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package java.util; |
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import java.util.*; // for javadoc (till 6280605 is fixed) |
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/** |
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* An unbounded priority {@linkplain Queue queue} based on a priority |
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* heap. The elements of the priority queue are ordered according to |
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* their {@linkplain Comparable natural ordering}, or by a {@link |
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* Comparator} provided at queue construction time, depending on which |
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* constructor is used. A priority queue does not permit |
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* <tt>null</tt> elements. A priority queue relying on natural |
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* ordering also does not permit insertion of non-comparable objects |
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* (doing so may result in <tt>ClassCastException</tt>). |
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* An unbounded priority {@linkplain Queue queue} based on a priority heap. |
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* The elements of the priority queue are ordered according to their |
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* {@linkplain Comparable natural ordering}, or by a {@link Comparator} |
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* provided at queue construction time, depending on which constructor is |
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* used. A priority queue does not permit {@code null} elements. |
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* A priority queue relying on natural ordering also does not permit |
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* insertion of non-comparable objects (doing so may result in |
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* {@code ClassCastException}). |
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* |
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* <p>The <em>head</em> of this queue is the <em>least</em> element |
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* with respect to the specified ordering. If multiple elements are |
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* tied for least value, the head is one of those elements -- ties are |
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* broken arbitrarily. The queue retrieval operations <tt>poll</tt>, |
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* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the |
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* broken arbitrarily. The queue retrieval operations {@code poll}, |
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* {@code remove}, {@code peek}, and {@code element} access the |
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* element at the head of the queue. |
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* |
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* <p>A priority queue is unbounded, but has an internal |
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* Iterator} interfaces. The Iterator provided in method {@link |
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* #iterator()} is <em>not</em> guaranteed to traverse the elements of |
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* the priority queue in any particular order. If you need ordered |
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* traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>. |
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* traversal, consider using {@code Arrays.sort(pq.toArray())}. |
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* |
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* <p> <strong>Note that this implementation is not synchronized.</strong> |
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* Multiple threads should not access a <tt>PriorityQueue</tt> |
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* instance concurrently if any of the threads modifies the list |
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* structurally. Instead, use the thread-safe {@link |
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* Multiple threads should not access a {@code PriorityQueue} |
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* instance concurrently if any of the threads modifies the queue. |
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* Instead, use the thread-safe {@link |
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* java.util.concurrent.PriorityBlockingQueue} class. |
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* |
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* <p>Implementation note: this implementation provides O(log(n)) time |
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* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>, |
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* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the |
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* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and |
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* constant time for the retrieval methods (<tt>peek</tt>, |
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* <tt>element</tt>, and <tt>size</tt>). |
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* <p>Implementation note: this implementation provides |
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* O(log(n)) time for the enqueing and dequeing methods |
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* ({@code offer}, {@code poll}, {@code remove()} and {@code add}); |
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* linear time for the {@code remove(Object)} and {@code contains(Object)} |
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* methods; and constant time for the retrieval methods |
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* ({@code peek}, {@code element}, and {@code size}). |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.5 |
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* @version 1.8, 08/27/05 |
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* @author Josh Bloch |
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* @version %I%, %G% |
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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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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 children |
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* of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is |
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* ordered by comparator, or by the elements' natural ordering, if |
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* comparator is null: For each node n in the heap and each descendant d |
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* of n, n <= d. |
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* |
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* The element with the lowest value is in queue[1], assuming the queue is |
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* nonempty. (A one-based array is used in preference to the traditional |
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* zero-based array to simplify parent and child calculations.) |
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* |
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* queue.length must be >= 2, even if size == 0. |
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* Priority queue represented as a balanced binary heap: the two |
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* children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The |
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* priority queue is ordered by comparator, or by the elements' |
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* natural ordering, if comparator is null: For each node n in the |
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* heap and each descendant d of n, n <= d. The element with the |
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* lowest value is in queue[0], assuming the queue is nonempty. |
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*/ |
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private transient Object[] queue; |
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private transient int modCount = 0; |
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/** |
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* Creates a <tt>PriorityQueue</tt> with the default initial |
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* Creates a {@code PriorityQueue} with the default initial |
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* capacity (11) that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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*/ |
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} |
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/** |
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* Creates a <tt>PriorityQueue</tt> with the specified initial |
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* Creates a {@code PriorityQueue} with the specified initial |
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* capacity that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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* |
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* @param initialCapacity the initial capacity for this priority queue |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
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* than 1 |
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* @throws IllegalArgumentException if {@code initialCapacity} is less |
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* than 1 |
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*/ |
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public PriorityQueue(int initialCapacity) { |
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this(initialCapacity, null); |
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} |
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/** |
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* Creates a <tt>PriorityQueue</tt> with the specified initial capacity |
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* Creates a {@code PriorityQueue} with the specified initial capacity |
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* that orders its elements according to the specified comparator. |
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* |
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* @param initialCapacity the initial capacity for this priority queue |
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* @param comparator the comparator that will be used to order |
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* this priority queue. If <tt>null</tt>, the <i>natural |
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* ordering</i> of the elements will be used. |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is |
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* @param comparator the comparator that will be used to order this |
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* priority queue. If {@code null}, the {@linkplain Comparable |
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* natural ordering} of the elements will be used. |
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> |
* @throws IllegalArgumentException if {@code initialCapacity} is |
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* less than 1 |
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*/ |
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public PriorityQueue(int initialCapacity, |
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Comparator<? super E> comparator) { |
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// Note: This restriction of at least one is not actually needed, |
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// but continues for 1.5 compatibility |
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if (initialCapacity < 1) |
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throw new IllegalArgumentException(); |
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this.queue = new Object[initialCapacity + 1]; |
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> |
this.queue = new Object[initialCapacity]; |
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this.comparator = comparator; |
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} |
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|
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/** |
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* Common code to initialize underlying queue array across |
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* constructors below. |
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*/ |
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private void initializeArray(Collection<? extends E> c) { |
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int sz = c.size(); |
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int initialCapacity = (int)Math.min((sz * 110L) / 100, |
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Integer.MAX_VALUE - 1); |
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if (initialCapacity < 1) |
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initialCapacity = 1; |
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|
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this.queue = new Object[initialCapacity + 1]; |
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} |
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|
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/** |
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* Initially fill elements of the queue array under the |
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* knowledge that it is sorted or is another PQ, in which |
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* case we can just place the elements in the order presented. |
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*/ |
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private void fillFromSorted(Collection<? extends E> c) { |
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) { |
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int k = ++size; |
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if (k >= queue.length) |
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grow(k); |
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queue[k] = i.next(); |
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} |
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} |
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|
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/** |
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* Initially fill elements of the queue array that is not to our knowledge |
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* sorted, so we must rearrange the elements to guarantee the heap |
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* invariant. |
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*/ |
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private void fillFromUnsorted(Collection<? extends E> c) { |
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for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) { |
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int k = ++size; |
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if (k >= queue.length) |
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grow(k); |
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queue[k] = i.next(); |
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} |
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heapify(); |
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} |
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|
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/** |
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* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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* specified collection. The priority queue has an initial |
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* capacity of 110% of the size of the specified collection or 1 |
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* if the collection is empty. If the specified collection is an |
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* instance of a {@link java.util.SortedSet} or is another |
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* <tt>PriorityQueue</tt>, the priority queue will be ordered |
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* according to the same ordering. Otherwise, this priority queue |
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< |
* will be ordered according to the natural ordering of its elements. |
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> |
* Creates a {@code PriorityQueue} containing the elements in the |
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> |
* specified collection. If the specified collection is an instance of |
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> |
* a {@link SortedSet} or is another {@code PriorityQueue}, this |
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> |
* priority queue will be ordered according to the same ordering. |
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> |
* Otherwise, this priority queue will be ordered according to the |
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> |
* {@linkplain Comparable natural ordering} of its elements. |
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* |
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* @param c the collection whose elements are to be placed |
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* into this priority queue |
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* of its elements are null |
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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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< |
SortedSet<? extends E> s = (SortedSet<? extends E>)c; |
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< |
comparator = (Comparator<? super E>)s.comparator(); |
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< |
fillFromSorted(s); |
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< |
} else if (c instanceof PriorityQueue) { |
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< |
PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c; |
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comparator = (Comparator<? super E>)s.comparator(); |
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fillFromSorted(s); |
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} else { |
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> |
initFromCollection(c); |
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> |
if (c instanceof SortedSet) |
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comparator = (Comparator<? super E>) |
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> |
((SortedSet<? extends E>)c).comparator(); |
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> |
else if (c instanceof PriorityQueue) |
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> |
comparator = (Comparator<? super E>) |
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> |
((PriorityQueue<? extends E>)c).comparator(); |
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> |
else { |
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comparator = null; |
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< |
fillFromUnsorted(c); |
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> |
heapify(); |
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} |
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} |
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|
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/** |
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< |
* Creates a <tt>PriorityQueue</tt> containing the elements in the |
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< |
* specified priority queue. The priority queue has an initial |
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< |
* capacity of 110% of the size of the specified priority queue or |
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< |
* 1 if the priority queue is empty. This priority queue will be |
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> |
* Creates a {@code PriorityQueue} containing the elements in the |
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> |
* specified priority queue. This priority queue will be |
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* ordered according to the same ordering as the given priority |
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* queue. |
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* |
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* @param c the priority queue whose elements are to be placed |
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* into this priority queue |
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< |
* @throws ClassCastException if elements of <tt>c</tt> cannot be |
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< |
* compared to one another according to <tt>c</tt>'s |
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> |
* @throws ClassCastException if elements of {@code c} cannot be |
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> |
* compared to one another according to {@code c}'s |
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* ordering |
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* @throws NullPointerException if the specified priority queue or any |
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* of its elements are null |
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*/ |
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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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> |
initFromCollection(c); |
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} |
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|
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/** |
| 190 |
< |
* Creates a <tt>PriorityQueue</tt> containing the elements in the |
| 191 |
< |
* specified sorted set. The priority queue has an initial |
| 245 |
< |
* capacity of 110% of the size of the specified sorted set or 1 |
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< |
* if the sorted set is empty. This priority queue will be ordered |
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> |
* Creates a {@code PriorityQueue} containing the elements in the |
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> |
* specified sorted set. This priority queue will be ordered |
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* according to the same ordering as the given sorted set. |
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* |
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* @param c the sorted set whose elements are to be placed |
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< |
* into this priority queue. |
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> |
* into this priority queue |
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* @throws ClassCastException if elements of the specified sorted |
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* set cannot be compared to one another according to the |
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* sorted set's ordering |
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* of its elements are null |
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*/ |
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public PriorityQueue(SortedSet<? extends E> c) { |
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initializeArray(c); |
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comparator = (Comparator<? super E>)c.comparator(); |
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< |
fillFromSorted(c); |
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> |
initFromCollection(c); |
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> |
} |
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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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> |
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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> |
queue = a; |
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> |
size = a.length; |
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} |
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|
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/** |
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< |
* Resize array, if necessary, to be able to hold given index. |
| 222 |
> |
* Increases the capacity of the array. |
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> |
* |
| 224 |
> |
* @param minCapacity the desired minimum capacity |
| 225 |
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*/ |
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< |
private void grow(int index) { |
| 227 |
< |
int newlen = queue.length; |
| 268 |
< |
if (index < newlen) // don't need to grow |
| 269 |
< |
return; |
| 270 |
< |
if (index == Integer.MAX_VALUE) |
| 226 |
> |
private void grow(int minCapacity) { |
| 227 |
> |
if (minCapacity < 0) // overflow |
| 228 |
|
throw new OutOfMemoryError(); |
| 229 |
< |
while (newlen <= index) { |
| 230 |
< |
if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow |
| 231 |
< |
newlen = Integer.MAX_VALUE; |
| 232 |
< |
else |
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< |
newlen <<= 2; |
| 234 |
< |
} |
| 235 |
< |
queue = Arrays.copyOf(queue, newlen); |
| 229 |
> |
int oldCapacity = queue.length; |
| 230 |
> |
// Double size if small; else grow by 50% |
| 231 |
> |
int newCapacity = ((oldCapacity < 64)? |
| 232 |
> |
((oldCapacity + 1) * 2): |
| 233 |
> |
((oldCapacity / 2) * 3)); |
| 234 |
> |
if (newCapacity < 0) // overflow |
| 235 |
> |
newCapacity = Integer.MAX_VALUE; |
| 236 |
> |
if (newCapacity < minCapacity) |
| 237 |
> |
newCapacity = minCapacity; |
| 238 |
> |
queue = Arrays.copyOf(queue, newCapacity); |
| 239 |
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} |
| 240 |
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|
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/** |
| 242 |
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* Inserts the specified element into this priority queue. |
| 243 |
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* |
| 244 |
< |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
| 244 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
| 245 |
|
* @throws ClassCastException if the specified element cannot be |
| 246 |
|
* compared with elements currently in this priority queue |
| 247 |
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* according to the priority queue's ordering |
| 254 |
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/** |
| 255 |
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* Inserts the specified element into this priority queue. |
| 256 |
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* |
| 257 |
< |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| 257 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
| 258 |
|
* @throws ClassCastException if the specified element cannot be |
| 259 |
|
* compared with elements currently in this priority queue |
| 260 |
|
* according to the priority queue's ordering |
| 264 |
|
if (e == null) |
| 265 |
|
throw new NullPointerException(); |
| 266 |
|
modCount++; |
| 267 |
< |
++size; |
| 268 |
< |
|
| 269 |
< |
// Grow backing store if necessary |
| 270 |
< |
if (size >= queue.length) |
| 271 |
< |
grow(size); |
| 272 |
< |
|
| 273 |
< |
queue[size] = e; |
| 274 |
< |
fixUp(size); |
| 267 |
> |
int i = size; |
| 268 |
> |
if (i >= queue.length) |
| 269 |
> |
grow(i + 1); |
| 270 |
> |
size = i + 1; |
| 271 |
> |
if (i == 0) |
| 272 |
> |
queue[0] = e; |
| 273 |
> |
else |
| 274 |
> |
siftUp(i, e); |
| 275 |
|
return true; |
| 276 |
|
} |
| 277 |
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|
| 278 |
|
public E peek() { |
| 279 |
|
if (size == 0) |
| 280 |
|
return null; |
| 281 |
< |
return (E) queue[1]; |
| 281 |
> |
return (E) queue[0]; |
| 282 |
|
} |
| 283 |
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|
| 284 |
|
private int indexOf(Object o) { |
| 285 |
< |
if (o == null) |
| 286 |
< |
return -1; |
| 287 |
< |
for (int i = 1; i <= size; i++) |
| 288 |
< |
if (o.equals(queue[i])) |
| 289 |
< |
return i; |
| 285 |
> |
if (o != null) { |
| 286 |
> |
for (int i = 0; i < size; i++) |
| 287 |
> |
if (o.equals(queue[i])) |
| 288 |
> |
return i; |
| 289 |
> |
} |
| 290 |
|
return -1; |
| 291 |
|
} |
| 292 |
|
|
| 293 |
|
/** |
| 294 |
|
* Removes a single instance of the specified element from this queue, |
| 295 |
< |
* if it is present. More formally, removes an element <tt>e</tt> such |
| 296 |
< |
* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
| 297 |
< |
* elements. Returns true if this queue contained the specified element |
| 298 |
< |
* (or equivalently, if this queue changed as a result of the call). |
| 295 |
> |
* if it is present. More formally, removes an element {@code e} such |
| 296 |
> |
* that {@code o.equals(e)}, if this queue contains one or more such |
| 297 |
> |
* elements. Returns {@code true} if and only if this queue contained |
| 298 |
> |
* the specified element (or equivalently, if this queue changed as a |
| 299 |
> |
* result of the call). |
| 300 |
|
* |
| 301 |
|
* @param o element to be removed from this queue, if present |
| 302 |
< |
* @return <tt>true</tt> if this queue changed as a result of the call |
| 302 |
> |
* @return {@code true} if this queue changed as a result of the call |
| 303 |
|
*/ |
| 304 |
|
public boolean remove(Object o) { |
| 305 |
|
int i = indexOf(o); |
| 312 |
|
} |
| 313 |
|
|
| 314 |
|
/** |
| 315 |
< |
* Returns <tt>true</tt> if this queue contains the specified element. |
| 316 |
< |
* More formally, returns <tt>true</tt> if and only if this queue contains |
| 317 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 315 |
> |
* Version of remove using reference equality, not equals. |
| 316 |
> |
* Needed by iterator.remove. |
| 317 |
> |
* |
| 318 |
> |
* @param o element to be removed from this queue, if present |
| 319 |
> |
* @return {@code true} if removed |
| 320 |
> |
*/ |
| 321 |
> |
boolean removeEq(Object o) { |
| 322 |
> |
for (int i = 0; i < size; i++) { |
| 323 |
> |
if (o == queue[i]) { |
| 324 |
> |
removeAt(i); |
| 325 |
> |
return true; |
| 326 |
> |
} |
| 327 |
> |
} |
| 328 |
> |
return false; |
| 329 |
> |
} |
| 330 |
> |
|
| 331 |
> |
/** |
| 332 |
> |
* Returns {@code true} if this queue contains the specified element. |
| 333 |
> |
* More formally, returns {@code true} if and only if this queue contains |
| 334 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
| 335 |
|
* |
| 336 |
|
* @param o object to be checked for containment in this queue |
| 337 |
< |
* @return <tt>true</tt> if this queue contains the specified element |
| 337 |
> |
* @return {@code true} if this queue contains the specified element |
| 338 |
|
*/ |
| 339 |
|
public boolean contains(Object o) { |
| 340 |
|
return indexOf(o) != -1; |
| 341 |
|
} |
| 342 |
|
|
| 343 |
|
/** |
| 344 |
< |
* Returns an array containing all of the elements in this queue, |
| 344 |
> |
* Returns an array containing all of the elements in this queue. |
| 345 |
|
* The elements are in no particular order. |
| 346 |
|
* |
| 347 |
|
* <p>The returned array will be "safe" in that no references to it are |
| 348 |
< |
* maintained by this list. (In other words, this method must allocate |
| 348 |
> |
* maintained by this queue. (In other words, this method must allocate |
| 349 |
|
* a new array). The caller is thus free to modify the returned array. |
| 350 |
|
* |
| 351 |
< |
* @return an array containing all of the elements in this queue. |
| 351 |
> |
* <p>This method acts as bridge between array-based and collection-based |
| 352 |
> |
* APIs. |
| 353 |
> |
* |
| 354 |
> |
* @return an array containing all of the elements in this queue |
| 355 |
|
*/ |
| 356 |
|
public Object[] toArray() { |
| 357 |
< |
return Arrays.copyOfRange(queue, 1, size+1); |
| 357 |
> |
return Arrays.copyOf(queue, size); |
| 358 |
|
} |
| 359 |
|
|
| 360 |
|
/** |
| 361 |
< |
* Returns an array containing all of the elements in this queue. |
| 362 |
< |
* The elements are in no particular order. The runtime type of |
| 363 |
< |
* the returned array is that of the specified array. If the queue |
| 364 |
< |
* fits in the specified array, it is returned therein. |
| 365 |
< |
* Otherwise, a new array is allocated with the runtime type of |
| 366 |
< |
* the specified array and the size of this queue. |
| 361 |
> |
* Returns an array containing all of the elements in this queue; the |
| 362 |
> |
* runtime type of the returned array is that of the specified array. |
| 363 |
> |
* The returned array elements are in no particular order. |
| 364 |
> |
* If the queue fits in the specified array, it is returned therein. |
| 365 |
> |
* Otherwise, a new array is allocated with the runtime type of the |
| 366 |
> |
* specified array and the size of this queue. |
| 367 |
|
* |
| 368 |
|
* <p>If the queue fits in the specified array with room to spare |
| 369 |
|
* (i.e., the array has more elements than the queue), the element in |
| 370 |
|
* the array immediately following the end of the collection is set to |
| 371 |
< |
* <tt>null</tt>. (This is useful in determining the length of the |
| 372 |
< |
* queue <i>only</i> if the caller knows that the queue does not contain |
| 373 |
< |
* any null elements.) |
| 371 |
> |
* {@code null}. |
| 372 |
> |
* |
| 373 |
> |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
| 374 |
> |
* array-based and collection-based APIs. Further, this method allows |
| 375 |
> |
* precise control over the runtime type of the output array, and may, |
| 376 |
> |
* under certain circumstances, be used to save allocation costs. |
| 377 |
> |
* |
| 378 |
> |
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. |
| 379 |
> |
* The following code can be used to dump the queue into a newly |
| 380 |
> |
* allocated array of <tt>String</tt>: |
| 381 |
> |
* |
| 382 |
> |
* <pre> |
| 383 |
> |
* String[] y = x.toArray(new String[0]);</pre> |
| 384 |
> |
* |
| 385 |
> |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| 386 |
> |
* <tt>toArray()</tt>. |
| 387 |
|
* |
| 388 |
|
* @param a the array into which the elements of the queue are to |
| 389 |
|
* be stored, if it is big enough; otherwise, a new array of the |
| 390 |
|
* same runtime type is allocated for this purpose. |
| 391 |
< |
* @return an array containing the elements of the queue |
| 391 |
> |
* @return an array containing all of the elements in this queue |
| 392 |
|
* @throws ArrayStoreException if the runtime type of the specified array |
| 393 |
|
* is not a supertype of the runtime type of every element in |
| 394 |
|
* this queue |
| 397 |
|
public <T> T[] toArray(T[] a) { |
| 398 |
|
if (a.length < size) |
| 399 |
|
// Make a new array of a's runtime type, but my contents: |
| 400 |
< |
return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass()); |
| 401 |
< |
System.arraycopy(queue, 1, a, 0, size); |
| 400 |
> |
return (T[]) Arrays.copyOf(queue, size, a.getClass()); |
| 401 |
> |
System.arraycopy(queue, 0, a, 0, size); |
| 402 |
|
if (a.length > size) |
| 403 |
|
a[size] = null; |
| 404 |
|
return a; |
| 414 |
|
return new Itr(); |
| 415 |
|
} |
| 416 |
|
|
| 417 |
< |
private class Itr implements Iterator<E> { |
| 424 |
< |
|
| 417 |
> |
private final class Itr implements Iterator<E> { |
| 418 |
|
/** |
| 419 |
|
* Index (into queue array) of element to be returned by |
| 420 |
|
* subsequent call to next. |
| 421 |
|
*/ |
| 422 |
< |
private int cursor = 1; |
| 422 |
> |
private int cursor = 0; |
| 423 |
|
|
| 424 |
|
/** |
| 425 |
|
* Index of element returned by most recent call to next, |
| 426 |
|
* unless that element came from the forgetMeNot list. |
| 427 |
< |
* Reset to 0 if element is deleted by a call to remove. |
| 427 |
> |
* Set to -1 if element is deleted by a call to remove. |
| 428 |
|
*/ |
| 429 |
< |
private int lastRet = 0; |
| 429 |
> |
private int lastRet = -1; |
| 430 |
|
|
| 431 |
|
/** |
| 432 |
< |
* The modCount value that the iterator believes that the backing |
| 440 |
< |
* List should have. If this expectation is violated, the iterator |
| 441 |
< |
* has detected concurrent modification. |
| 442 |
< |
*/ |
| 443 |
< |
private int expectedModCount = modCount; |
| 444 |
< |
|
| 445 |
< |
/** |
| 446 |
< |
* A list of elements that were moved from the unvisited portion of |
| 432 |
> |
* A queue of elements that were moved from the unvisited portion of |
| 433 |
|
* the heap into the visited portion as a result of "unlucky" element |
| 434 |
|
* removals during the iteration. (Unlucky element removals are those |
| 435 |
< |
* that require a fixup instead of a fixdown.) We must visit all of |
| 435 |
> |
* that require a siftup instead of a siftdown.) We must visit all of |
| 436 |
|
* the elements in this list to complete the iteration. We do this |
| 437 |
|
* after we've completed the "normal" iteration. |
| 438 |
|
* |
| 439 |
|
* We expect that most iterations, even those involving removals, |
| 440 |
< |
* will not use need to store elements in this field. |
| 440 |
> |
* will not need to store elements in this field. |
| 441 |
|
*/ |
| 442 |
< |
private ArrayList<E> forgetMeNot = null; |
| 442 |
> |
private ArrayDeque<E> forgetMeNot = null; |
| 443 |
|
|
| 444 |
|
/** |
| 445 |
|
* Element returned by the most recent call to next iff that |
| 446 |
|
* element was drawn from the forgetMeNot list. |
| 447 |
|
*/ |
| 448 |
< |
private Object lastRetElt = null; |
| 448 |
> |
private E lastRetElt = null; |
| 449 |
> |
|
| 450 |
> |
/** |
| 451 |
> |
* The modCount value that the iterator believes that the backing |
| 452 |
> |
* Queue should have. If this expectation is violated, the iterator |
| 453 |
> |
* has detected concurrent modification. |
| 454 |
> |
*/ |
| 455 |
> |
private int expectedModCount = modCount; |
| 456 |
|
|
| 457 |
|
public boolean hasNext() { |
| 458 |
< |
return cursor <= size || forgetMeNot != null; |
| 458 |
> |
return cursor < size || |
| 459 |
> |
(forgetMeNot != null && !forgetMeNot.isEmpty()); |
| 460 |
|
} |
| 461 |
|
|
| 462 |
|
public E next() { |
| 463 |
< |
checkForComodification(); |
| 464 |
< |
E result; |
| 465 |
< |
if (cursor <= size) { |
| 466 |
< |
result = (E) queue[cursor]; |
| 467 |
< |
lastRet = cursor++; |
| 468 |
< |
} |
| 469 |
< |
else if (forgetMeNot == null) |
| 470 |
< |
throw new NoSuchElementException(); |
| 471 |
< |
else { |
| 478 |
< |
int remaining = forgetMeNot.size(); |
| 479 |
< |
result = forgetMeNot.remove(remaining - 1); |
| 480 |
< |
if (remaining == 1) |
| 481 |
< |
forgetMeNot = null; |
| 482 |
< |
lastRet = 0; |
| 483 |
< |
lastRetElt = result; |
| 463 |
> |
if (expectedModCount != modCount) |
| 464 |
> |
throw new ConcurrentModificationException(); |
| 465 |
> |
if (cursor < size) |
| 466 |
> |
return (E) queue[lastRet = cursor++]; |
| 467 |
> |
if (forgetMeNot != null) { |
| 468 |
> |
lastRet = -1; |
| 469 |
> |
lastRetElt = forgetMeNot.poll(); |
| 470 |
> |
if (lastRetElt != null) |
| 471 |
> |
return lastRetElt; |
| 472 |
|
} |
| 473 |
< |
return result; |
| 473 |
> |
throw new NoSuchElementException(); |
| 474 |
|
} |
| 475 |
|
|
| 476 |
|
public void remove() { |
| 477 |
< |
checkForComodification(); |
| 478 |
< |
|
| 479 |
< |
if (lastRet != 0) { |
| 477 |
> |
if (expectedModCount != modCount) |
| 478 |
> |
throw new ConcurrentModificationException(); |
| 479 |
> |
if (lastRet != -1) { |
| 480 |
|
E moved = PriorityQueue.this.removeAt(lastRet); |
| 481 |
< |
lastRet = 0; |
| 482 |
< |
if (moved == null) { |
| 481 |
> |
lastRet = -1; |
| 482 |
> |
if (moved == null) |
| 483 |
|
cursor--; |
| 484 |
< |
} else { |
| 484 |
> |
else { |
| 485 |
|
if (forgetMeNot == null) |
| 486 |
< |
forgetMeNot = new ArrayList<E>(); |
| 486 |
> |
forgetMeNot = new ArrayDeque<E>(); |
| 487 |
|
forgetMeNot.add(moved); |
| 488 |
|
} |
| 489 |
|
} else if (lastRetElt != null) { |
| 490 |
< |
PriorityQueue.this.remove(lastRetElt); |
| 490 |
> |
PriorityQueue.this.removeEq(lastRetElt); |
| 491 |
|
lastRetElt = null; |
| 492 |
|
} else { |
| 493 |
|
throw new IllegalStateException(); |
| 494 |
< |
} |
| 507 |
< |
|
| 494 |
> |
} |
| 495 |
|
expectedModCount = modCount; |
| 496 |
|
} |
| 510 |
– |
|
| 511 |
– |
final void checkForComodification() { |
| 512 |
– |
if (modCount != expectedModCount) |
| 513 |
– |
throw new ConcurrentModificationException(); |
| 514 |
– |
} |
| 497 |
|
} |
| 498 |
|
|
| 499 |
|
public int size() { |
| 506 |
|
*/ |
| 507 |
|
public void clear() { |
| 508 |
|
modCount++; |
| 509 |
< |
|
| 528 |
< |
// Null out element references to prevent memory leak |
| 529 |
< |
for (int i=1; i<=size; i++) |
| 509 |
> |
for (int i = 0; i < size; i++) |
| 510 |
|
queue[i] = null; |
| 531 |
– |
|
| 511 |
|
size = 0; |
| 512 |
|
} |
| 513 |
|
|
| 514 |
|
public E poll() { |
| 515 |
|
if (size == 0) |
| 516 |
|
return null; |
| 517 |
+ |
int s = --size; |
| 518 |
|
modCount++; |
| 519 |
< |
|
| 520 |
< |
E result = (E) queue[1]; |
| 521 |
< |
queue[1] = queue[size]; |
| 522 |
< |
queue[size--] = null; // Drop extra ref to prevent memory leak |
| 523 |
< |
if (size > 1) |
| 544 |
< |
fixDown(1); |
| 545 |
< |
|
| 519 |
> |
E result = (E) queue[0]; |
| 520 |
> |
E x = (E) queue[s]; |
| 521 |
> |
queue[s] = null; |
| 522 |
> |
if (s != 0) |
| 523 |
> |
siftDown(0, x); |
| 524 |
|
return result; |
| 525 |
|
} |
| 526 |
|
|
| 527 |
|
/** |
| 528 |
< |
* Removes and returns the ith element from queue. (Recall that queue |
| 551 |
< |
* is one-based, so 1 <= i <= size.) |
| 528 |
> |
* Removes the ith element from queue. |
| 529 |
|
* |
| 530 |
< |
* Normally this method leaves the elements at positions from 1 up to i-1, |
| 531 |
< |
* inclusive, untouched. Under these circumstances, it returns null. |
| 532 |
< |
* Occasionally, in order to maintain the heap invariant, it must move |
| 533 |
< |
* the last element of the list to some index in the range [2, i-1], |
| 534 |
< |
* and move the element previously at position (i/2) to position i. |
| 535 |
< |
* Under these circumstances, this method returns the element that was |
| 536 |
< |
* previously at the end of the list and is now at some position between |
| 537 |
< |
* 2 and i-1 inclusive. |
| 530 |
> |
* Normally this method leaves the elements at up to i-1, |
| 531 |
> |
* inclusive, untouched. Under these circumstances, it returns |
| 532 |
> |
* null. Occasionally, in order to maintain the heap invariant, |
| 533 |
> |
* it must swap a later element of the list with one earlier than |
| 534 |
> |
* i. Under these circumstances, this method returns the element |
| 535 |
> |
* that was previously at the end of the list and is now at some |
| 536 |
> |
* position before i. This fact is used by iterator.remove so as to |
| 537 |
> |
* avoid missing traversing elements. |
| 538 |
|
*/ |
| 539 |
|
private E removeAt(int i) { |
| 540 |
< |
assert i > 0 && i <= size; |
| 540 |
> |
assert i >= 0 && i < size; |
| 541 |
|
modCount++; |
| 542 |
< |
|
| 543 |
< |
E moved = (E) queue[size]; |
| 544 |
< |
queue[i] = moved; |
| 545 |
< |
queue[size--] = null; // Drop extra ref to prevent memory leak |
| 546 |
< |
if (i <= size) { |
| 547 |
< |
fixDown(i); |
| 542 |
> |
int s = --size; |
| 543 |
> |
if (s == i) // removed last element |
| 544 |
> |
queue[i] = null; |
| 545 |
> |
else { |
| 546 |
> |
E moved = (E) queue[s]; |
| 547 |
> |
queue[s] = null; |
| 548 |
> |
siftDown(i, moved); |
| 549 |
|
if (queue[i] == moved) { |
| 550 |
< |
fixUp(i); |
| 550 |
> |
siftUp(i, moved); |
| 551 |
|
if (queue[i] != moved) |
| 552 |
|
return moved; |
| 553 |
|
} |
| 556 |
|
} |
| 557 |
|
|
| 558 |
|
/** |
| 559 |
< |
* Establishes the heap invariant (described above) assuming the heap |
| 560 |
< |
* satisfies the invariant except possibly for the leaf-node indexed by k |
| 561 |
< |
* (which may have a nextExecutionTime less than its parent's). |
| 562 |
< |
* |
| 563 |
< |
* This method functions by "promoting" queue[k] up the hierarchy |
| 564 |
< |
* (by swapping it with its parent) repeatedly until queue[k] |
| 565 |
< |
* is greater than or equal to its parent. |
| 566 |
< |
*/ |
| 567 |
< |
private void fixUp(int k) { |
| 568 |
< |
if (comparator == null) { |
| 569 |
< |
while (k > 1) { |
| 570 |
< |
int j = k >> 1; |
| 571 |
< |
if (((Comparable<? super E>)queue[j]).compareTo((E)queue[k]) <= 0) |
| 572 |
< |
break; |
| 573 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 574 |
< |
k = j; |
| 575 |
< |
} |
| 576 |
< |
} else { |
| 577 |
< |
while (k > 1) { |
| 578 |
< |
int j = k >>> 1; |
| 579 |
< |
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
| 580 |
< |
break; |
| 581 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 582 |
< |
k = j; |
| 583 |
< |
} |
| 584 |
< |
} |
| 585 |
< |
} |
| 586 |
< |
|
| 587 |
< |
/** |
| 588 |
< |
* Establishes the heap invariant (described above) in the subtree |
| 589 |
< |
* rooted at k, which is assumed to satisfy the heap invariant except |
| 590 |
< |
* possibly for node k itself (which may be greater than its children). |
| 591 |
< |
* |
| 592 |
< |
* This method functions by "demoting" queue[k] down the hierarchy |
| 593 |
< |
* (by swapping it with its smaller child) repeatedly until queue[k] |
| 594 |
< |
* is less than or equal to its children. |
| 595 |
< |
*/ |
| 596 |
< |
private void fixDown(int k) { |
| 597 |
< |
int j; |
| 598 |
< |
if (comparator == null) { |
| 599 |
< |
while ((j = k << 1) <= size && (j > 0)) { |
| 600 |
< |
if (j<size && |
| 601 |
< |
((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
| 602 |
< |
j++; // j indexes smallest kid |
| 603 |
< |
|
| 604 |
< |
if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0) |
| 605 |
< |
break; |
| 606 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 607 |
< |
k = j; |
| 608 |
< |
} |
| 609 |
< |
} else { |
| 610 |
< |
while ((j = k << 1) <= size && (j > 0)) { |
| 611 |
< |
if (j<size && |
| 612 |
< |
comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
| 613 |
< |
j++; // j indexes smallest kid |
| 614 |
< |
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
| 615 |
< |
break; |
| 616 |
< |
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 617 |
< |
k = j; |
| 618 |
< |
} |
| 559 |
> |
* Inserts item x at position k, maintaining heap invariant by |
| 560 |
> |
* promoting x up the tree until it is greater than or equal to |
| 561 |
> |
* its parent, or is the root. |
| 562 |
> |
* |
| 563 |
> |
* To simplify and speed up coercions and comparisons. the |
| 564 |
> |
* Comparable and Comparator versions are separated into different |
| 565 |
> |
* methods that are otherwise identical. (Similarly for siftDown.) |
| 566 |
> |
* |
| 567 |
> |
* @param k the position to fill |
| 568 |
> |
* @param x the item to insert |
| 569 |
> |
*/ |
| 570 |
> |
private void siftUp(int k, E x) { |
| 571 |
> |
if (comparator != null) |
| 572 |
> |
siftUpUsingComparator(k, x); |
| 573 |
> |
else |
| 574 |
> |
siftUpComparable(k, x); |
| 575 |
> |
} |
| 576 |
> |
|
| 577 |
> |
private void siftUpComparable(int k, E x) { |
| 578 |
> |
Comparable<? super E> key = (Comparable<? super E>) x; |
| 579 |
> |
while (k > 0) { |
| 580 |
> |
int parent = (k - 1) >>> 1; |
| 581 |
> |
Object e = queue[parent]; |
| 582 |
> |
if (key.compareTo((E) e) >= 0) |
| 583 |
> |
break; |
| 584 |
> |
queue[k] = e; |
| 585 |
> |
k = parent; |
| 586 |
> |
} |
| 587 |
> |
queue[k] = key; |
| 588 |
> |
} |
| 589 |
> |
|
| 590 |
> |
private void siftUpUsingComparator(int k, E x) { |
| 591 |
> |
while (k > 0) { |
| 592 |
> |
int parent = (k - 1) >>> 1; |
| 593 |
> |
Object e = queue[parent]; |
| 594 |
> |
if (comparator.compare(x, (E) e) >= 0) |
| 595 |
> |
break; |
| 596 |
> |
queue[k] = e; |
| 597 |
> |
k = parent; |
| 598 |
> |
} |
| 599 |
> |
queue[k] = x; |
| 600 |
> |
} |
| 601 |
> |
|
| 602 |
> |
/** |
| 603 |
> |
* Inserts item x at position k, maintaining heap invariant by |
| 604 |
> |
* demoting x down the tree repeatedly until it is less than or |
| 605 |
> |
* equal to its children or is a leaf. |
| 606 |
> |
* |
| 607 |
> |
* @param k the position to fill |
| 608 |
> |
* @param x the item to insert |
| 609 |
> |
*/ |
| 610 |
> |
private void siftDown(int k, E x) { |
| 611 |
> |
if (comparator != null) |
| 612 |
> |
siftDownUsingComparator(k, x); |
| 613 |
> |
else |
| 614 |
> |
siftDownComparable(k, x); |
| 615 |
> |
} |
| 616 |
> |
|
| 617 |
> |
private void siftDownComparable(int k, E x) { |
| 618 |
> |
Comparable<? super E> key = (Comparable<? super E>)x; |
| 619 |
> |
int half = size >>> 1; // loop while a non-leaf |
| 620 |
> |
while (k < half) { |
| 621 |
> |
int child = (k << 1) + 1; // assume left child is least |
| 622 |
> |
Object c = queue[child]; |
| 623 |
> |
int right = child + 1; |
| 624 |
> |
if (right < size && |
| 625 |
> |
((Comparable<? super E>) c).compareTo((E) queue[right]) > 0) |
| 626 |
> |
c = queue[child = right]; |
| 627 |
> |
if (key.compareTo((E) c) <= 0) |
| 628 |
> |
break; |
| 629 |
> |
queue[k] = c; |
| 630 |
> |
k = child; |
| 631 |
> |
} |
| 632 |
> |
queue[k] = key; |
| 633 |
> |
} |
| 634 |
> |
|
| 635 |
> |
private void siftDownUsingComparator(int k, E x) { |
| 636 |
> |
int half = size >>> 1; |
| 637 |
> |
while (k < half) { |
| 638 |
> |
int child = (k << 1) + 1; |
| 639 |
> |
Object c = queue[child]; |
| 640 |
> |
int right = child + 1; |
| 641 |
> |
if (right < size && |
| 642 |
> |
comparator.compare((E) c, (E) queue[right]) > 0) |
| 643 |
> |
c = queue[child = right]; |
| 644 |
> |
if (comparator.compare(x, (E) c) <= 0) |
| 645 |
> |
break; |
| 646 |
> |
queue[k] = c; |
| 647 |
> |
k = child; |
| 648 |
|
} |
| 649 |
+ |
queue[k] = x; |
| 650 |
|
} |
| 651 |
|
|
| 652 |
|
/** |
| 654 |
|
* assuming nothing about the order of the elements prior to the call. |
| 655 |
|
*/ |
| 656 |
|
private void heapify() { |
| 657 |
< |
for (int i = size/2; i >= 1; i--) |
| 658 |
< |
fixDown(i); |
| 657 |
> |
for (int i = (size >>> 1) - 1; i >= 0; i--) |
| 658 |
> |
siftDown(i, (E) queue[i]); |
| 659 |
|
} |
| 660 |
|
|
| 661 |
|
/** |
| 662 |
|
* Returns the comparator used to order the elements in this |
| 663 |
< |
* queue, or <tt>null</tt> if this queue is sorted according to |
| 663 |
> |
* queue, or {@code null} if this queue is sorted according to |
| 664 |
|
* the {@linkplain Comparable natural ordering} of its elements. |
| 665 |
|
* |
| 666 |
|
* @return the comparator used to order this queue, or |
| 667 |
< |
* <tt>null</tt> if this queue is sorted according to the |
| 668 |
< |
* natural ordering of its elements. |
| 667 |
> |
* {@code null} if this queue is sorted according to the |
| 668 |
> |
* natural ordering of its elements |
| 669 |
|
*/ |
| 670 |
|
public Comparator<? super E> comparator() { |
| 671 |
|
return comparator; |
| 672 |
|
} |
| 673 |
|
|
| 674 |
|
/** |
| 675 |
< |
* Save the state of the instance to a stream (that |
| 676 |
< |
* is, serialize it). |
| 675 |
> |
* Saves the state of the instance to a stream (that |
| 676 |
> |
* is, serializes it). |
| 677 |
|
* |
| 678 |
|
* @serialData The length of the array backing the instance is |
| 679 |
< |
* emitted (int), followed by all of its elements (each an |
| 680 |
< |
* <tt>Object</tt>) in the proper order. |
| 679 |
> |
* emitted (int), followed by all of its elements |
| 680 |
> |
* (each an {@code Object}) in the proper order. |
| 681 |
|
* @param s the stream |
| 682 |
|
*/ |
| 683 |
|
private void writeObject(java.io.ObjectOutputStream s) |
| 685 |
|
// Write out element count, and any hidden stuff |
| 686 |
|
s.defaultWriteObject(); |
| 687 |
|
|
| 688 |
< |
// Write out array length |
| 689 |
< |
s.writeInt(queue.length); |
| 688 |
> |
// Write out array length, for compatibility with 1.5 version |
| 689 |
> |
s.writeInt(Math.max(2, size + 1)); |
| 690 |
|
|
| 691 |
< |
// Write out all elements in the proper order. |
| 692 |
< |
for (int i=1; i<=size; i++) |
| 691 |
> |
// Write out all elements in the "proper order". |
| 692 |
> |
for (int i = 0; i < size; i++) |
| 693 |
|
s.writeObject(queue[i]); |
| 694 |
|
} |
| 695 |
|
|
| 696 |
|
/** |
| 697 |
< |
* Reconstitute the <tt>PriorityQueue</tt> instance from a stream |
| 698 |
< |
* (that is, deserialize it). |
| 697 |
> |
* Reconstitutes the {@code PriorityQueue} instance from a stream |
| 698 |
> |
* (that is, deserializes it). |
| 699 |
> |
* |
| 700 |
|
* @param s the stream |
| 701 |
|
*/ |
| 702 |
|
private void readObject(java.io.ObjectInputStream s) |
| 704 |
|
// Read in size, and any hidden stuff |
| 705 |
|
s.defaultReadObject(); |
| 706 |
|
|
| 707 |
< |
// Read in array length and allocate array |
| 708 |
< |
int arrayLength = s.readInt(); |
| 700 |
< |
queue = new Object[arrayLength]; |
| 701 |
< |
|
| 702 |
< |
// Read in all elements in the proper order. |
| 703 |
< |
for (int i=1; i<=size; i++) |
| 704 |
< |
queue[i] = (E) s.readObject(); |
| 705 |
< |
} |
| 707 |
> |
// Read in (and discard) array length |
| 708 |
> |
s.readInt(); |
| 709 |
|
|
| 710 |
+ |
queue = new Object[size]; |
| 711 |
+ |
|
| 712 |
+ |
// Read in all elements. |
| 713 |
+ |
for (int i = 0; i < size; i++) |
| 714 |
+ |
queue[i] = s.readObject(); |
| 715 |
+ |
|
| 716 |
+ |
// Elements are guaranteed to be in "proper order", but the |
| 717 |
+ |
// spec has never explained what that might be. |
| 718 |
+ |
heapify(); |
| 719 |
+ |
} |
| 720 |
|
} |
