/*
	* Copyright (C) 2003-2019 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.ints;
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 trim() method to reduce its size, if necessary. /**
 * A type-specific heap-based priority queue.
 *
 * <p>
 * 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 IntHeapPriorityQueue implements IntPriorityQueue, java.io.Serializable {
	private static final long serialVersionUID = 1L;
	
The heap array. /** The heap array. */

	protected transient int[] heap = IntArrays.EMPTY_ARRAY;
	
The number of elements in this queue. /** The number of elements in this queue. */
	protected int size;
	
The type-specific comparator used in this queue. /** The type-specific comparator used in this queue. */
	protected IntComparator c;
	
Creates a new empty queue with a given capacity and comparator.
Params:
capacity – 
           the initial capacity of this queue.
c –  the comparator used in this queue, or null for the natural order./**
	 * 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 IntHeapPriorityQueue(int capacity, IntComparator c) {
		if (capacity > 0)
			this.heap = new int[capacity];
		this.c = c;
	}
	
Creates a new empty queue with a given capacity and using the natural order.
Params:
capacity – 
           the initial capacity of this queue./**
	 * Creates a new empty queue with a given capacity and using the natural order.
	 *
	 * @param capacity
	 *            the initial capacity of this queue.
	 */
	public IntHeapPriorityQueue(int capacity) {
		this(capacity, null);
	}
	
Creates a new empty queue with a given comparator.
Params:
c –  the comparator used in this queue, or null for the natural order./**
	 * 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 IntHeapPriorityQueue(IntComparator c) {
		this(0, c);
	}
	
Creates a new empty queue using the natural order.
/**
	 * Creates a new empty queue using the natural order.
	 */
	public IntHeapPriorityQueue() {
		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 size element of the array will be rearranged so to form a heap (this is more efficient than enqueing the elements of a one by one). 
Params:
a – 
           an array.
size – 
           the number of elements to be included in the queue.
c –  the comparator used in this queue, or null for the natural order./**
	 * Wraps a given array in a queue using a given comparator.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final int[] a, int size, final IntComparator c) {
		this(c);
		this.heap = a;
		this.size = size;
		IntHeaps.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 a one by one). 
Params:
a – 
           an array.
c –  the comparator used in this queue, or null for the natural order./**
	 * Wraps a given array in a queue using a given comparator.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final int[] a, final IntComparator 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 size element of the array will be rearranged so to form a heap (this is more efficient than enqueing the elements of a one by one). 
Params:
a – 
           an array.
size – 
           the number of elements to be included in the queue./**
	 * Wraps a given array in a queue using the natural order.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final int[] 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 a one by one). 
Params:
a – 
           an array./**
	 * Wraps a given array in a queue using the natural order.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final int[] 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 collection one by one. 
Params:
collection – 
           a collection; its elements will be used to initialize the queue.
c –  the comparator used in this queue, or null for the natural order./**
	 * Creates a queue using the elements in a type-specific collection using a
	 * given comparator.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final IntCollection collection, final IntComparator c) {
		this(collection.toIntArray(), 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 collection one by one. 
Params:
collection – 
           a collection; its elements will be used to initialize the queue./**
	 * Creates a queue using the elements in a type-specific collection using the
	 * natural order.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final IntCollection 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 collection one by one. 
Params:
collection – 
           a collection; its elements will be used to initialize the queue.
c –  the comparator used in this queue, or null for the natural order./**
	 * Creates a queue using the elements in a collection using a given comparator.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final Collection<? extends Integer> collection, final IntComparator c) {
		this(collection.size(), c);
		final Iterator<? extends Integer> iterator = collection.iterator();
		final int size = collection.size();
		for (int i = 0; i < size; i++)
			heap[i] = ((Integer) (iterator.next())).intValue();
	}
	
Creates a queue using the elements in a collection using the natural order.
 This constructor is more efficient than enqueing the elements of collection one by one. 
Params:
collection – 
           a collection; its elements will be used to initialize the queue./**
	 * Creates a queue using the elements in a collection using the natural order.
	 *
	 * <p>
	 * 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 IntHeapPriorityQueue(final Collection<? extends Integer> collection) {
		this(collection, null);
	}
	@Override
	public void enqueue(int x) {
		if (size == heap.length)
			heap = IntArrays.grow(heap, size + 1);
		heap[size++] = x;
		IntHeaps.upHeap(heap, size, size - 1, c);
	}
	@Override
	public int dequeueInt() {
		if (size == 0)
			throw new NoSuchElementException();
		final int result = heap[0];
		heap[0] = heap[--size];
		if (size != 0)
			IntHeaps.downHeap(heap, size, 0, c);
		return result;
	}
	@Override
	public int firstInt() {
		if (size == 0)
			throw new NoSuchElementException();
		return heap[0];
	}
	@Override
	public void changed() {
		IntHeaps.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 size() elements. /**
	 * Trims the underlying heap array so that it has exactly {@link #size()}
	 * elements.
	 */
	public void trim() {
		heap = IntArrays.trim(heap, size);
	}
	@Override
	public IntComparator comparator() {
		return c;
	}
	private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
		s.defaultWriteObject();
		s.writeInt(heap.length);
		for (int i = 0; i < size; i++)
			s.writeInt(heap[i]);
	}

	private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
		s.defaultReadObject();
		heap = new int[s.readInt()];
		for (int i = 0; i < size; i++)
			heap[i] = s.readInt();
	}
}