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/*
* Copyright (C) 2003-2024 Paolo Boldi and Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package it.unimi.dsi.fastutil.bytes;
import java.util.Iterator;
import java.util.Collection;
import java.util.NoSuchElementException;
/** A type-specific heap-based priority queue.
*
* Instances of this class represent a priority queue using a heap. The heap is enlarged as needed, but
* it is never shrunk. Use the {@link #trim()} method to reduce its size, if necessary.
*/
public class ByteHeapPriorityQueue implements BytePriorityQueue , java.io.Serializable {
private static final long serialVersionUID = 1L;
/** The heap array. */
protected transient byte[] heap = ByteArrays.EMPTY_ARRAY;
/** The number of elements in this queue. */
protected int size;
/** The type-specific comparator used in this queue. */
protected ByteComparator c;
/** Creates a new empty queue with a given capacity and comparator.
*
* @param capacity the initial capacity of this queue.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ByteHeapPriorityQueue(int capacity, ByteComparator c) {
if (capacity > 0) this.heap = new byte[capacity];
this.c = c;
}
/** Creates a new empty queue with a given capacity and using the natural order.
*
* @param capacity the initial capacity of this queue.
*/
public ByteHeapPriorityQueue(int capacity) {
this(capacity, null);
}
/** Creates a new empty queue with a given comparator.
*
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ByteHeapPriorityQueue(ByteComparator c) {
this(0, c);
}
/** Creates a new empty queue using the natural order.
*/
public ByteHeapPriorityQueue() {
this(0, null);
}
/** Wraps a given array in a queue using a given comparator.
*
*
The queue returned by this method will be backed by the given array.
* The first {@code size} element of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of {@code a} one by one).
*
* @param a an array.
* @param size the number of elements to be included in the queue.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ByteHeapPriorityQueue(final byte[] a, int size, final ByteComparator c) {
this(c);
this.heap = a;
this.size = size;
ByteHeaps.makeHeap(a, size, c);
}
/** Wraps a given array in a queue using a given comparator.
*
*
The queue returned by this method will be backed by the given array.
* The elements of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of {@code a} one by one).
*
* @param a an array.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ByteHeapPriorityQueue(final byte[] a, final ByteComparator c) {
this(a, a.length, c);
}
/** Wraps a given array in a queue using the natural order.
*
*
The queue returned by this method will be backed by the given array.
* The first {@code size} element of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of {@code a} one by one).
*
* @param a an array.
* @param size the number of elements to be included in the queue.
*/
public ByteHeapPriorityQueue(final byte[] a, int size) {
this(a, size, null);
}
/** Wraps a given array in a queue using the natural order.
*
*
The queue returned by this method will be backed by the given array.
* The elements of the array will be rearranged so to form a heap (this is
* more efficient than enqueing the elements of {@code a} one by one).
*
* @param a an array.
*/
public ByteHeapPriorityQueue(final byte[] a) {
this(a, a.length);
}
/** Creates a queue using the elements in a type-specific collection using a given comparator.
*
*
This constructor is more efficient than enqueing the elements of {@code collection} one by one.
*
* @param collection a collection; its elements will be used to initialize the queue.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ByteHeapPriorityQueue(final ByteCollection collection, final ByteComparator c) {
this(collection.toByteArray(), c);
}
/** Creates a queue using the elements in a type-specific collection using the natural order.
*
*
This constructor is
* more efficient than enqueing the elements of {@code collection} one by one.
*
* @param collection a collection; its elements will be used to initialize the queue.
*/
public ByteHeapPriorityQueue(final ByteCollection collection) {
this(collection, null);
}
/** Creates a queue using the elements in a collection using a given comparator.
*
*
This constructor is more efficient than enqueing the elements of {@code collection} one by one.
*
* @param collection a collection; its elements will be used to initialize the queue.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ByteHeapPriorityQueue(final Collection collection, final ByteComparator c) {
this(collection.size(), c);
final Iterator iterator = collection.iterator();
final int size = collection.size();
for(int i = 0 ; i < size; i++) heap[i] = ((Byte)(iterator.next())).byteValue();
}
/** Creates a queue using the elements in a collection using the natural order.
*
*
This constructor is
* more efficient than enqueing the elements of {@code collection} one by one.
*
* @param collection a collection; its elements will be used to initialize the queue.
*/
public ByteHeapPriorityQueue(final Collection collection) {
this(collection, null);
}
@Override
public void enqueue(byte x) {
if (size == heap.length) heap = ByteArrays.grow(heap, size + 1);
heap[size++] = x;
ByteHeaps.upHeap(heap, size, size - 1, c);
}
@Override
public byte dequeueByte() {
if (size == 0) throw new NoSuchElementException();
final byte result = heap[0];
heap[0] = heap[--size];
if (size != 0) ByteHeaps.downHeap(heap, size, 0, c);
return result;
}
@Override
public byte firstByte() {
if (size == 0) throw new NoSuchElementException();
return heap[0];
}
@Override
public void changed() {
ByteHeaps.downHeap(heap, size, 0, c);
}
@Override
public int size() { return size; }
@Override
public void clear() {
size = 0;
}
/** Trims the underlying heap array so that it has exactly {@link #size()} elements. */
public void trim() {
heap = ByteArrays.trim(heap, size);
}
@Override
public ByteComparator comparator() { return c; }
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
s.defaultWriteObject();
s.writeInt(heap.length);
final byte[] heap = this.heap;
for(int i = 0; i < size; i++) s.writeByte(heap[i]);
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
final byte[] heap = this.heap = new byte[s.readInt()];
for(int i = 0; i < size; i++) heap[i] = s.readByte();
}
}