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package java.util; |
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/* |
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* @(#)PriorityQueue.java 1.8 05/08/27 |
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* |
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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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 heap. |
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* 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 java.util.TreeSet} and |
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* {@link java.util.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 java.util.Comparator}, depending on which |
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* constructor is used. |
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* <p>The <em>head</em> of this queue is the <em>least</em> element with |
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* respect to the specified ordering. |
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* If multiple elements are tied for least value, the |
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* head is one of those elements. A priority queue does not permit |
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* <tt>null</tt> elements. |
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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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* |
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* <p>The {@link #remove()} and {@link #poll()} methods remove and |
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* return the head of the queue. |
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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>The {@link #element()} and {@link #peek()} methods return, but do |
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* not delete, the head of the queue. |
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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>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. |
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* 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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* |
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* <p>The 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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* <p>This class and its iterator implement all of the |
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* <em>optional</em> methods of the {@link Collection} and {@link |
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* Iterator} interfaces. The Iterator provided in method {@link |
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* #iterator()} is <em>not</em> guaranteed to traverse the elements of |
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* the priority queue in any particular order. If you need ordered |
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* traversal, consider using <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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* 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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* <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 1.8, 08/27/05 |
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* @author Josh Bloch |
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* @param <E> the type of elements held in this collection |
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*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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implements Queue<E>, java.io.Serializable { |
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implements java.io.Serializable { |
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private static final long serialVersionUID = -7720805057305804111L; |
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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 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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* Creates a <tt>PriorityQueue</tt> with the default initial |
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* capacity (11) that orders its elements according to their |
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* {@linkplain Comparable natural ordering}. |
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*/ |
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public PriorityQueue() { |
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this(DEFAULT_INITIAL_CAPACITY, null); |
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} |
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/** |
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* Creates a <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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* Creates a <tt>PriorityQueue</tt> 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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* @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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* 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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* @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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* less than 1 |
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*/ |
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public PriorityQueue(int initialCapacity, |
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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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throw new IllegalArgumentException(); |
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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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* 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 without fixups. |
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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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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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/** |
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* Initially fill elements of the queue array that is |
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* not to our knowledge sorted, so we must add them |
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* one by one. |
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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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add(i.next()); |
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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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* 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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* <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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* |
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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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* @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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* queue's ordering |
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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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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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> |
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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|
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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. |
| 234 |
< |
* @throws NullPointerException if <tt>c</tt> or any element within it |
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< |
* is <tt>null</tt> |
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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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> |
* ordered according to the same ordering as the given priority |
| 226 |
> |
* queue. |
| 227 |
> |
* |
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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 |
| 231 |
> |
* compared to one another according to <tt>c</tt>'s |
| 232 |
> |
* ordering |
| 233 |
> |
* @throws NullPointerException if the specified priority queue or any |
| 234 |
> |
* of its elements are null |
| 235 |
|
*/ |
| 236 |
|
public PriorityQueue(PriorityQueue<? extends E> c) { |
| 237 |
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initializeArray(c); |
| 241 |
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|
| 242 |
|
/** |
| 243 |
|
* Creates a <tt>PriorityQueue</tt> containing the elements in the |
| 244 |
< |
* specified collection. The priority queue has an initial |
| 245 |
< |
* capacity of 110% of the size of the specified collection or 1 |
| 246 |
< |
* if the collection is empty. This priority queue will be sorted |
| 247 |
< |
* according to the same comparator as the given collection, or |
| 248 |
< |
* according to its elements' natural order if the collection is |
| 249 |
< |
* sorted according to its elements' natural order. |
| 250 |
< |
* |
| 251 |
< |
* @param c the collection whose elements are to be placed |
| 252 |
< |
* into this priority queue. |
| 253 |
< |
* @throws ClassCastException if elements of the specified collection |
| 254 |
< |
* cannot be compared to one another according to the priority |
| 255 |
< |
* queue's ordering. |
| 245 |
< |
* @throws NullPointerException if <tt>c</tt> or any element within it |
| 246 |
< |
* is <tt>null</tt> |
| 244 |
> |
* specified sorted set. The priority queue has an initial |
| 245 |
> |
* capacity of 110% of the size of the specified sorted set or 1 |
| 246 |
> |
* if the sorted set is empty. This priority queue will be ordered |
| 247 |
> |
* according to the same ordering as the given sorted set. |
| 248 |
> |
* |
| 249 |
> |
* @param c the sorted set whose elements are to be placed |
| 250 |
> |
* into this priority queue. |
| 251 |
> |
* @throws ClassCastException if elements of the specified sorted |
| 252 |
> |
* set cannot be compared to one another according to the |
| 253 |
> |
* sorted set's ordering |
| 254 |
> |
* @throws NullPointerException if the specified sorted set or any |
| 255 |
> |
* of its elements are null |
| 256 |
|
*/ |
| 257 |
|
public PriorityQueue(SortedSet<? extends E> c) { |
| 258 |
|
initializeArray(c); |
| 261 |
|
} |
| 262 |
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|
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|
/** |
| 264 |
< |
* Resize array, if necessary, to be able to hold given index |
| 264 |
> |
* Resize array, if necessary, to be able to hold given index. |
| 265 |
|
*/ |
| 266 |
|
private void grow(int index) { |
| 267 |
|
int newlen = queue.length; |
| 273 |
|
if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow |
| 274 |
|
newlen = Integer.MAX_VALUE; |
| 275 |
|
else |
| 276 |
< |
newlen <<= 2; |
| 276 |
> |
newlen <<= 1; |
| 277 |
|
} |
| 278 |
< |
Object[] newQueue = new Object[newlen]; |
| 270 |
< |
System.arraycopy(queue, 0, newQueue, 0, queue.length); |
| 271 |
< |
queue = newQueue; |
| 278 |
> |
queue = Arrays.copyOf(queue, newlen); |
| 279 |
|
} |
| 273 |
– |
|
| 274 |
– |
// Queue Methods |
| 275 |
– |
|
| 280 |
|
|
| 281 |
+ |
/** |
| 282 |
+ |
* Inserts the specified element into this priority queue. |
| 283 |
+ |
* |
| 284 |
+ |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
| 285 |
+ |
* @throws ClassCastException if the specified element cannot be |
| 286 |
+ |
* compared with elements currently in this priority queue |
| 287 |
+ |
* according to the priority queue's ordering |
| 288 |
+ |
* @throws NullPointerException if the specified element is null |
| 289 |
+ |
*/ |
| 290 |
+ |
public boolean add(E e) { |
| 291 |
+ |
return offer(e); |
| 292 |
+ |
} |
| 293 |
|
|
| 294 |
|
/** |
| 295 |
< |
* Add the specified element to this priority queue. |
| 295 |
> |
* Inserts the specified element into this priority queue. |
| 296 |
|
* |
| 297 |
< |
* @return <tt>true</tt> |
| 298 |
< |
* @throws ClassCastException if the specified element cannot be compared |
| 299 |
< |
* with elements currently in the priority queue according |
| 300 |
< |
* to the priority queue's ordering. |
| 301 |
< |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
| 297 |
> |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| 298 |
> |
* @throws ClassCastException if the specified element cannot be |
| 299 |
> |
* compared with elements currently in this priority queue |
| 300 |
> |
* according to the priority queue's ordering |
| 301 |
> |
* @throws NullPointerException if the specified element is null |
| 302 |
|
*/ |
| 303 |
< |
public boolean offer(E o) { |
| 304 |
< |
if (o == null) |
| 303 |
> |
public boolean offer(E e) { |
| 304 |
> |
if (e == null) |
| 305 |
|
throw new NullPointerException(); |
| 306 |
|
modCount++; |
| 307 |
|
++size; |
| 308 |
|
|
| 309 |
|
// Grow backing store if necessary |
| 310 |
< |
if (size >= queue.length) |
| 310 |
> |
if (size >= queue.length) |
| 311 |
|
grow(size); |
| 312 |
|
|
| 313 |
< |
queue[size] = o; |
| 313 |
> |
queue[size] = e; |
| 314 |
|
fixUp(size); |
| 315 |
|
return true; |
| 316 |
|
} |
| 317 |
|
|
| 318 |
< |
public E poll() { |
| 318 |
> |
public E peek() { |
| 319 |
|
if (size == 0) |
| 320 |
|
return null; |
| 305 |
– |
return (E) remove(1); |
| 306 |
– |
} |
| 307 |
– |
|
| 308 |
– |
public E peek() { |
| 321 |
|
return (E) queue[1]; |
| 322 |
|
} |
| 323 |
|
|
| 324 |
< |
// Collection Methods - the first two override to update docs |
| 324 |
> |
private int indexOf(Object o) { |
| 325 |
> |
if (o == null) |
| 326 |
> |
return -1; |
| 327 |
> |
for (int i = 1; i <= size; i++) |
| 328 |
> |
if (o.equals(queue[i])) |
| 329 |
> |
return i; |
| 330 |
> |
return -1; |
| 331 |
> |
} |
| 332 |
|
|
| 333 |
|
/** |
| 334 |
< |
* Adds the specified element to this queue. |
| 335 |
< |
* @return <tt>true</tt> (as per the general contract of |
| 336 |
< |
* <tt>Collection.add</tt>). |
| 337 |
< |
* |
| 338 |
< |
* @throws NullPointerException {@inheritDoc} |
| 339 |
< |
* @throws ClassCastException if the specified element cannot be compared |
| 340 |
< |
* with elements currently in the priority queue according |
| 341 |
< |
* to the priority queue's ordering. |
| 342 |
< |
*/ |
| 343 |
< |
public boolean add(E o) { |
| 344 |
< |
return super.add(o); |
| 345 |
< |
} |
| 346 |
< |
|
| 347 |
< |
|
| 348 |
< |
/** |
| 349 |
< |
* Adds all of the elements in the specified collection to this queue. |
| 350 |
< |
* The behavior of this operation is undefined if |
| 332 |
< |
* the specified collection is modified while the operation is in |
| 333 |
< |
* progress. (This implies that the behavior of this call is undefined if |
| 334 |
< |
* the specified collection is this queue, and this queue is nonempty.) |
| 335 |
< |
* <p> |
| 336 |
< |
* This implementation iterates over the specified collection, and adds |
| 337 |
< |
* each object returned by the iterator to this collection, in turn. |
| 338 |
< |
* @throws NullPointerException {@inheritDoc} |
| 339 |
< |
* @throws ClassCastException if any element cannot be compared |
| 340 |
< |
* with elements currently in the priority queue according |
| 341 |
< |
* to the priority queue's ordering. |
| 342 |
< |
*/ |
| 343 |
< |
public boolean addAll(Collection<? extends E> c) { |
| 344 |
< |
return super.addAll(c); |
| 334 |
> |
* Removes a single instance of the specified element from this queue, |
| 335 |
> |
* if it is present. More formally, removes an element <tt>e</tt> such |
| 336 |
> |
* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
| 337 |
> |
* elements. Returns true if this queue contained the specified element |
| 338 |
> |
* (or equivalently, if this queue changed as a result of the call). |
| 339 |
> |
* |
| 340 |
> |
* @param o element to be removed from this queue, if present |
| 341 |
> |
* @return <tt>true</tt> if this queue changed as a result of the call |
| 342 |
> |
*/ |
| 343 |
> |
public boolean remove(Object o) { |
| 344 |
> |
int i = indexOf(o); |
| 345 |
> |
if (i == -1) |
| 346 |
> |
return false; |
| 347 |
> |
else { |
| 348 |
> |
removeAt(i); |
| 349 |
> |
return true; |
| 350 |
> |
} |
| 351 |
|
} |
| 352 |
|
|
| 353 |
+ |
/** |
| 354 |
+ |
* Returns <tt>true</tt> if this queue contains the specified element. |
| 355 |
+ |
* More formally, returns <tt>true</tt> if and only if this queue contains |
| 356 |
+ |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 357 |
+ |
* |
| 358 |
+ |
* @param o object to be checked for containment in this queue |
| 359 |
+ |
* @return <tt>true</tt> if this queue contains the specified element |
| 360 |
+ |
*/ |
| 361 |
+ |
public boolean contains(Object o) { |
| 362 |
+ |
return indexOf(o) != -1; |
| 363 |
+ |
} |
| 364 |
|
|
| 365 |
< |
/** |
| 366 |
< |
* Removes a single instance of the specified element from this |
| 367 |
< |
* queue, if it is present. More formally, |
| 368 |
< |
* removes an element <tt>e</tt> such that <tt>(o==null ? e==null : |
| 369 |
< |
* o.equals(e))</tt>, if the queue contains one or more such |
| 370 |
< |
* elements. Returns <tt>true</tt> if the queue contained the |
| 371 |
< |
* specified element (or equivalently, if the queue changed as a |
| 355 |
< |
* result of the call). |
| 356 |
< |
* |
| 357 |
< |
* <p>This implementation iterates over the queue looking for the |
| 358 |
< |
* specified element. If it finds the element, it removes the element |
| 359 |
< |
* from the queue using the iterator's remove method.<p> |
| 365 |
> |
/** |
| 366 |
> |
* Returns an array containing all of the elements in this queue, |
| 367 |
> |
* The elements are in no particular order. |
| 368 |
> |
* |
| 369 |
> |
* <p>The returned array will be "safe" in that no references to it are |
| 370 |
> |
* maintained by this list. (In other words, this method must allocate |
| 371 |
> |
* a new array). The caller is thus free to modify the returned array. |
| 372 |
|
* |
| 373 |
+ |
* @return an array containing all of the elements in this queue. |
| 374 |
|
*/ |
| 375 |
< |
public boolean remove(Object o) { |
| 376 |
< |
if (o == null) |
| 377 |
< |
return false; |
| 375 |
> |
public Object[] toArray() { |
| 376 |
> |
return Arrays.copyOfRange(queue, 1, size+1); |
| 377 |
> |
} |
| 378 |
|
|
| 379 |
< |
if (comparator == null) { |
| 380 |
< |
for (int i = 1; i <= size; i++) { |
| 381 |
< |
if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) { |
| 382 |
< |
remove(i); |
| 383 |
< |
return true; |
| 384 |
< |
} |
| 385 |
< |
} |
| 386 |
< |
} else { |
| 387 |
< |
for (int i = 1; i <= size; i++) { |
| 388 |
< |
if (comparator.compare((E)queue[i], (E)o) == 0) { |
| 389 |
< |
remove(i); |
| 390 |
< |
return true; |
| 391 |
< |
} |
| 392 |
< |
} |
| 393 |
< |
} |
| 394 |
< |
return false; |
| 379 |
> |
/** |
| 380 |
> |
* Returns an array containing all of the elements in this queue. |
| 381 |
> |
* The elements are in no particular order. The runtime type of |
| 382 |
> |
* the returned array is that of the specified array. If the queue |
| 383 |
> |
* fits in the specified array, it is returned therein. |
| 384 |
> |
* Otherwise, a new array is allocated with the runtime type of |
| 385 |
> |
* the specified array and the size of this queue. |
| 386 |
> |
* |
| 387 |
> |
* <p>If the queue fits in the specified array with room to spare |
| 388 |
> |
* (i.e., the array has more elements than the queue), the element in |
| 389 |
> |
* the array immediately following the end of the collection is set to |
| 390 |
> |
* <tt>null</tt>. (This is useful in determining the length of the |
| 391 |
> |
* queue <i>only</i> if the caller knows that the queue does not contain |
| 392 |
> |
* any null elements.) |
| 393 |
> |
* |
| 394 |
> |
* @param a the array into which the elements of the queue are to |
| 395 |
> |
* be stored, if it is big enough; otherwise, a new array of the |
| 396 |
> |
* same runtime type is allocated for this purpose. |
| 397 |
> |
* @return an array containing the elements of the queue |
| 398 |
> |
* @throws ArrayStoreException if the runtime type of the specified array |
| 399 |
> |
* is not a supertype of the runtime type of every element in |
| 400 |
> |
* this queue |
| 401 |
> |
* @throws NullPointerException if the specified array is null |
| 402 |
> |
*/ |
| 403 |
> |
public <T> T[] toArray(T[] a) { |
| 404 |
> |
if (a.length < size) |
| 405 |
> |
// Make a new array of a's runtime type, but my contents: |
| 406 |
> |
return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass()); |
| 407 |
> |
System.arraycopy(queue, 1, a, 0, size); |
| 408 |
> |
if (a.length > size) |
| 409 |
> |
a[size] = null; |
| 410 |
> |
return a; |
| 411 |
|
} |
| 412 |
|
|
| 413 |
|
/** |
| 414 |
|
* Returns an iterator over the elements in this queue. The iterator |
| 415 |
|
* does not return the elements in any particular order. |
| 416 |
|
* |
| 417 |
< |
* @return an iterator over the elements in this queue. |
| 417 |
> |
* @return an iterator over the elements in this queue |
| 418 |
|
*/ |
| 419 |
|
public Iterator<E> iterator() { |
| 420 |
|
return new Itr(); |
| 421 |
|
} |
| 422 |
|
|
| 423 |
|
private class Itr implements Iterator<E> { |
| 424 |
+ |
|
| 425 |
|
/** |
| 426 |
|
* Index (into queue array) of element to be returned by |
| 427 |
|
* subsequent call to next. |
| 429 |
|
private int cursor = 1; |
| 430 |
|
|
| 431 |
|
/** |
| 432 |
< |
* Index of element returned by most recent call to next or |
| 433 |
< |
* previous. Reset to 0 if this element is deleted by a call |
| 434 |
< |
* to remove. |
| 432 |
> |
* Index of element returned by most recent call to next, |
| 433 |
> |
* unless that element came from the forgetMeNot list. |
| 434 |
> |
* Reset to 0 if element is deleted by a call to remove. |
| 435 |
|
*/ |
| 436 |
|
private int lastRet = 0; |
| 437 |
|
|
| 442 |
|
*/ |
| 443 |
|
private int expectedModCount = modCount; |
| 444 |
|
|
| 445 |
+ |
/** |
| 446 |
+ |
* A list of elements that were moved from the unvisited portion of |
| 447 |
+ |
* the heap into the visited portion as a result of "unlucky" element |
| 448 |
+ |
* removals during the iteration. (Unlucky element removals are those |
| 449 |
+ |
* that require a fixup instead of a fixdown.) We must visit all of |
| 450 |
+ |
* the elements in this list to complete the iteration. We do this |
| 451 |
+ |
* after we've completed the "normal" iteration. |
| 452 |
+ |
* |
| 453 |
+ |
* We expect that most iterations, even those involving removals, |
| 454 |
+ |
* will not use need to store elements in this field. |
| 455 |
+ |
*/ |
| 456 |
+ |
private ArrayList<E> forgetMeNot = null; |
| 457 |
+ |
|
| 458 |
+ |
/** |
| 459 |
+ |
* Element returned by the most recent call to next iff that |
| 460 |
+ |
* element was drawn from the forgetMeNot list. |
| 461 |
+ |
*/ |
| 462 |
+ |
private Object lastRetElt = null; |
| 463 |
+ |
|
| 464 |
|
public boolean hasNext() { |
| 465 |
< |
return cursor <= size; |
| 465 |
> |
return cursor <= size || forgetMeNot != null; |
| 466 |
|
} |
| 467 |
|
|
| 468 |
|
public E next() { |
| 469 |
|
checkForComodification(); |
| 470 |
< |
if (cursor > size) |
| 470 |
> |
E result; |
| 471 |
> |
if (cursor <= size) { |
| 472 |
> |
result = (E) queue[cursor]; |
| 473 |
> |
lastRet = cursor++; |
| 474 |
> |
} |
| 475 |
> |
else if (forgetMeNot == null) |
| 476 |
|
throw new NoSuchElementException(); |
| 477 |
< |
E result = (E) queue[cursor]; |
| 478 |
< |
lastRet = cursor++; |
| 477 |
> |
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; |
| 484 |
> |
} |
| 485 |
|
return result; |
| 486 |
|
} |
| 487 |
|
|
| 488 |
|
public void remove() { |
| 429 |
– |
if (lastRet == 0) |
| 430 |
– |
throw new IllegalStateException(); |
| 489 |
|
checkForComodification(); |
| 490 |
|
|
| 491 |
< |
PriorityQueue.this.remove(lastRet); |
| 492 |
< |
cursor--; |
| 493 |
< |
lastRet = 0; |
| 491 |
> |
if (lastRet != 0) { |
| 492 |
> |
E moved = PriorityQueue.this.removeAt(lastRet); |
| 493 |
> |
lastRet = 0; |
| 494 |
> |
if (moved == null) { |
| 495 |
> |
cursor--; |
| 496 |
> |
} else { |
| 497 |
> |
if (forgetMeNot == null) |
| 498 |
> |
forgetMeNot = new ArrayList<E>(); |
| 499 |
> |
forgetMeNot.add(moved); |
| 500 |
> |
} |
| 501 |
> |
} else if (lastRetElt != null) { |
| 502 |
> |
PriorityQueue.this.remove(lastRetElt); |
| 503 |
> |
lastRetElt = null; |
| 504 |
> |
} else { |
| 505 |
> |
throw new IllegalStateException(); |
| 506 |
> |
} |
| 507 |
> |
|
| 508 |
|
expectedModCount = modCount; |
| 509 |
|
} |
| 510 |
|
|
| 519 |
|
} |
| 520 |
|
|
| 521 |
|
/** |
| 522 |
< |
* Remove all elements from the priority queue. |
| 522 |
> |
* Removes all of the elements from this priority queue. |
| 523 |
> |
* The queue will be empty after this call returns. |
| 524 |
|
*/ |
| 525 |
|
public void clear() { |
| 526 |
|
modCount++; |
| 532 |
|
size = 0; |
| 533 |
|
} |
| 534 |
|
|
| 535 |
+ |
public E poll() { |
| 536 |
+ |
if (size == 0) |
| 537 |
+ |
return null; |
| 538 |
+ |
modCount++; |
| 539 |
+ |
|
| 540 |
+ |
E result = (E) queue[1]; |
| 541 |
+ |
queue[1] = queue[size]; |
| 542 |
+ |
queue[size--] = null; // Drop extra ref to prevent memory leak |
| 543 |
+ |
if (size > 1) |
| 544 |
+ |
fixDown(1); |
| 545 |
+ |
|
| 546 |
+ |
return result; |
| 547 |
+ |
} |
| 548 |
+ |
|
| 549 |
|
/** |
| 550 |
< |
* Removes and returns the ith element from queue. Recall |
| 551 |
< |
* that queue is one-based, so 1 <= i <= size. |
| 550 |
> |
* Removes and returns the ith element from queue. (Recall that queue |
| 551 |
> |
* is one-based, so 1 <= i <= size.) |
| 552 |
|
* |
| 553 |
+ |
* Normally this method leaves the elements at positions from 1 up to i-1, |
| 554 |
+ |
* inclusive, untouched. Under these circumstances, it returns null. |
| 555 |
+ |
* Occasionally, in order to maintain the heap invariant, it must move |
| 556 |
+ |
* the last element of the list to some index in the range [2, i-1], |
| 557 |
+ |
* and move the element previously at position (i/2) to position i. |
| 558 |
+ |
* Under these circumstances, this method returns the element that was |
| 559 |
+ |
* previously at the end of the list and is now at some position between |
| 560 |
+ |
* 2 and i-1 inclusive. |
| 561 |
|
*/ |
| 562 |
< |
private E remove(int i) { |
| 563 |
< |
assert i <= size; |
| 562 |
> |
private E removeAt(int i) { |
| 563 |
> |
assert i > 0 && i <= size; |
| 564 |
|
modCount++; |
| 565 |
|
|
| 566 |
< |
E result = (E) queue[i]; |
| 567 |
< |
queue[i] = queue[size]; |
| 566 |
> |
E moved = (E) queue[size]; |
| 567 |
> |
queue[i] = moved; |
| 568 |
|
queue[size--] = null; // Drop extra ref to prevent memory leak |
| 569 |
< |
if (i <= size) |
| 569 |
> |
if (i <= size) { |
| 570 |
|
fixDown(i); |
| 571 |
< |
return result; |
| 571 |
> |
if (queue[i] == moved) { |
| 572 |
> |
fixUp(i); |
| 573 |
> |
if (queue[i] != moved) |
| 574 |
> |
return moved; |
| 575 |
> |
} |
| 576 |
> |
} |
| 577 |
> |
return null; |
| 578 |
|
} |
| 579 |
|
|
| 580 |
|
/** |
| 590 |
|
if (comparator == null) { |
| 591 |
|
while (k > 1) { |
| 592 |
|
int j = k >> 1; |
| 593 |
< |
if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0) |
| 593 |
> |
if (((Comparable<? super E>)queue[j]).compareTo((E)queue[k]) <= 0) |
| 594 |
|
break; |
| 595 |
|
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 596 |
|
k = j; |
| 597 |
|
} |
| 598 |
|
} else { |
| 599 |
|
while (k > 1) { |
| 600 |
< |
int j = k >> 1; |
| 600 |
> |
int j = k >>> 1; |
| 601 |
|
if (comparator.compare((E)queue[j], (E)queue[k]) <= 0) |
| 602 |
|
break; |
| 603 |
|
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 619 |
|
int j; |
| 620 |
|
if (comparator == null) { |
| 621 |
|
while ((j = k << 1) <= size && (j > 0)) { |
| 622 |
< |
if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
| 622 |
> |
if (j<size && |
| 623 |
> |
((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
| 624 |
|
j++; // j indexes smallest kid |
| 625 |
< |
if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
| 625 |
> |
|
| 626 |
> |
if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0) |
| 627 |
|
break; |
| 628 |
|
Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp; |
| 629 |
|
k = j; |
| 630 |
|
} |
| 631 |
|
} else { |
| 632 |
|
while ((j = k << 1) <= size && (j > 0)) { |
| 633 |
< |
if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
| 633 |
> |
if (j<size && |
| 634 |
> |
comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
| 635 |
|
j++; // j indexes smallest kid |
| 636 |
|
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |
| 637 |
|
break; |
| 641 |
|
} |
| 642 |
|
} |
| 643 |
|
|
| 644 |
+ |
/** |
| 645 |
+ |
* Establishes the heap invariant (described above) in the entire tree, |
| 646 |
+ |
* assuming nothing about the order of the elements prior to the call. |
| 647 |
+ |
*/ |
| 648 |
+ |
private void heapify() { |
| 649 |
+ |
for (int i = size/2; i >= 1; i--) |
| 650 |
+ |
fixDown(i); |
| 651 |
+ |
} |
| 652 |
|
|
| 653 |
|
/** |
| 654 |
< |
* Returns the comparator used to order this collection, or <tt>null</tt> |
| 655 |
< |
* if this collection is sorted according to its elements natural ordering |
| 656 |
< |
* (using <tt>Comparable</tt>). |
| 657 |
< |
* |
| 658 |
< |
* @return the comparator used to order this collection, or <tt>null</tt> |
| 659 |
< |
* if this collection is sorted according to its elements natural ordering. |
| 654 |
> |
* Returns the comparator used to order the elements in this |
| 655 |
> |
* queue, or <tt>null</tt> if this queue is sorted according to |
| 656 |
> |
* the {@linkplain Comparable natural ordering} of its elements. |
| 657 |
> |
* |
| 658 |
> |
* @return the comparator used to order this queue, or |
| 659 |
> |
* <tt>null</tt> if this queue is sorted according to the |
| 660 |
> |
* natural ordering of its elements. |
| 661 |
|
*/ |
| 662 |
|
public Comparator<? super E> comparator() { |
| 663 |
|
return comparator; |
| 681 |
|
s.writeInt(queue.length); |
| 682 |
|
|
| 683 |
|
// Write out all elements in the proper order. |
| 684 |
< |
for (int i=0; i<size; i++) |
| 684 |
> |
for (int i=1; i<=size; i++) |
| 685 |
|
s.writeObject(queue[i]); |
| 686 |
|
} |
| 687 |
|
|
| 688 |
|
/** |
| 689 |
< |
* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is, |
| 690 |
< |
* deserialize it). |
| 689 |
> |
* Reconstitute the <tt>PriorityQueue</tt> instance from a stream |
| 690 |
> |
* (that is, deserialize it). |
| 691 |
|
* @param s the stream |
| 692 |
|
*/ |
| 693 |
|
private void readObject(java.io.ObjectInputStream s) |
| 700 |
|
queue = new Object[arrayLength]; |
| 701 |
|
|
| 702 |
|
// Read in all elements in the proper order. |
| 703 |
< |
for (int i=0; i<size; i++) |
| 704 |
< |
queue[i] = s.readObject(); |
| 703 |
> |
for (int i=1; i<=size; i++) |
| 704 |
> |
queue[i] = (E) s.readObject(); |
| 705 |
|
} |
| 706 |
|
|
| 707 |
|
} |
| 595 |
– |
|
