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/** |
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* An unbounded priority queue based on a priority heap. This queue orders |
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* elements according to an order specified at construction time, which is |
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* specified in the same manner as {@link TreeSet} and {@link TreeMap}: |
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* specified in the same manner as {@link TreeSet} and {@link TreeMap}: |
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* elements are ordered |
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* either according to their <i>natural order</i> (see {@link Comparable}), or |
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* according to a {@link Comparator}, depending on which constructor is used. |
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* The <em>head</em> of this queue is the least element with respect to the |
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* specified ordering. 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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* specified ordering. 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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* |
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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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* |
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* @author Josh Bloch |
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*/ |
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public class PriorityQueue<E> extends AbstractQueue<E> |
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implements Queue<E>, Sorted, java.io.Serializable { |
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implements Queue<E>, java.io.Serializable { |
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|
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private static final int DEFAULT_INITIAL_CAPACITY = 11; |
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|
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* @param comparator the comparator used to order this priority queue. |
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* If <tt>null</tt> then the order depends on the elements' natural |
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* ordering. |
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* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less |
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* than 1 |
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*/ |
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public PriorityQueue(int initialCapacity, Comparator<E> comparator) { |
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if (initialCapacity < 1) |
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initialCapacity = 1; |
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throw new IllegalArgumentException(); |
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queue = (E[]) new Object[initialCapacity + 1]; |
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this.comparator = comparator; |
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} |
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/** |
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* Create a <tt>PriorityQueue</tt> containing the elements in the specified |
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* collection. The priority queue has an initial capacity of 110% of the |
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* size of the specified collection. If the specified collection |
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* size of the specified collection; or 1 if the collection is empty. |
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* If the specified collection |
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* implements the {@link Sorted} interface, the priority queue will be |
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* sorted according to the same comparator, or according to its elements' |
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* natural order if the collection is sorted according to its elements' |
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* <tt>Sorted</tt>, the priority queue is ordered according to |
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* its elements' natural order. |
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* |
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< |
* @param initialElements the collection whose elements are to be placed |
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> |
* @param c the collection whose elements are to be placed |
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* into this priority queue. |
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* @throws ClassCastException if elements of the specified collection |
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* cannot be compared to one another according to the priority |
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* queue's ordering. |
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* @throws NullPointerException if the specified collection or an |
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* element of the specified collection is <tt>null</tt>. |
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* @throws NullPointerException if <tt>c</tt> or any element within it |
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* is <tt>null</tt> |
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*/ |
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< |
public PriorityQueue(Collection<E> initialElements) { |
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< |
int sz = initialElements.size(); |
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> |
public PriorityQueue(Collection<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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queue = (E[]) new Object[initialCapacity + 1]; |
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|
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if (initialElements instanceof Sorted) { |
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< |
comparator = ((Sorted)initialElements).comparator(); |
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< |
for (Iterator<E> i = initialElements.iterator(); i.hasNext(); ) |
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> |
if (c instanceof Sorted) { |
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> |
// FIXME: this code assumes too much |
146 |
> |
comparator = ((Sorted)c).comparator(); |
147 |
> |
for (Iterator<E> i = c.iterator(); i.hasNext(); ) |
148 |
|
queue[++size] = i.next(); |
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} else { |
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comparator = null; |
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< |
for (Iterator<E> i = initialElements.iterator(); i.hasNext(); ) |
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> |
for (Iterator<E> i = c.iterator(); i.hasNext(); ) |
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add(i.next()); |
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} |
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} |
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|
|
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/** |
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* @throws NullPointerException if the specified element is <tt>null</tt>. |
202 |
+ |
* @throws ClassCastException if the specified element cannot be compared |
203 |
+ |
* with elements currently in the priority queue according |
204 |
+ |
* to the priority queue's ordering. |
205 |
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*/ |
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|
public boolean add(E element) { |
207 |
|
return super.add(element); |
208 |
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} |
209 |
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|
202 |
– |
// /** |
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– |
// * @throws NullPointerException if any element is <tt>null</tt>. |
204 |
– |
// */ |
205 |
– |
// public boolean addAll(Collection c) { |
206 |
– |
// return super.addAll(c); |
207 |
– |
// } |
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– |
|
210 |
|
/** |
211 |
< |
* @throws NullPointerException if the specified element is <tt>null</tt>. |
211 |
> |
* @throws NullPointerException if any element is <tt>null</tt>. |
212 |
> |
* @throws ClassCastException if any element cannot be compared |
213 |
> |
* with elements currently in the priority queue according |
214 |
> |
* to the priority queue's ordering. |
215 |
|
*/ |
216 |
+ |
public boolean addAll(Collection<? extends E> c) { |
217 |
+ |
return super.addAll(c); |
218 |
+ |
} |
219 |
+ |
|
220 |
|
public boolean remove(Object o) { |
221 |
|
if (o == null) |
222 |
< |
throw new NullPointerException(); |
222 |
> |
return false; |
223 |
|
|
224 |
|
if (comparator == null) { |
225 |
|
for (int i = 1; i <= size; i++) { |
239 |
|
return false; |
240 |
|
} |
241 |
|
|
234 |
– |
/** |
235 |
– |
* Returns an iterator over the elements in this priority queue. The |
236 |
– |
* elements of the priority queue will be returned by this iterator in the |
237 |
– |
* order specified by the queue, which is to say the order they would be |
238 |
– |
* returned by repeated calls to <tt>poll</tt>. |
239 |
– |
* |
240 |
– |
* @return an <tt>Iterator</tt> over the elements in this priority queue. |
241 |
– |
*/ |
242 |
|
public Iterator<E> iterator() { |
243 |
|
return new Itr(); |
244 |
|
} |