/*
	* 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.longs;
import java.util.NoSuchElementException;
A type-specific array-based priority queue.
 Instances of this class represent a priority queue using a backing array—all operations are performed directly on the array. The array is enlarged as needed, but it is never shrunk. Use the trim() method to reduce its size, if necessary. 

This implementation is extremely inefficient, but it is difficult to beat
when the size of the queue is very small.
/**
 * A type-specific array-based priority queue.
 *
 * <p>
 * Instances of this class represent a priority queue using a backing
 * array&mdash;all operations are performed directly on the array. The array is
 * enlarged as needed, but it is never shrunk. Use the {@link #trim()} method to
 * reduce its size, if necessary.
 *
 * <p>
 * This implementation is extremely inefficient, but it is difficult to beat
 * when the size of the queue is very small.
 */
public class LongArrayPriorityQueue implements LongPriorityQueue, java.io.Serializable {
	private static final long serialVersionUID = 1L;
	
The backing array. /** The backing array. */

	protected transient long array[] = LongArrays.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 LongComparator c;
	
The first index, cached, if firstIndexValid is true. /** The first index, cached, if {@link #firstIndexValid} is true. */
	protected transient int firstIndex;
	
Whether firstIndex contains a valid value. /** Whether {@link #firstIndex} contains a valid value. */
	protected transient boolean firstIndexValid;
	
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 LongArrayPriorityQueue(int capacity, LongComparator c) {
		if (capacity > 0)
			this.array = new long[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 LongArrayPriorityQueue(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 LongArrayPriorityQueue(LongComparator c) {
		this(0, c);
	}
	
Creates a new empty queue using the natural order.
/**
	 * Creates a new empty queue using the natural order.
	 */
	public LongArrayPriorityQueue() {
		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.
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.
	 *
	 * @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 LongArrayPriorityQueue(final long[] a, int size, final LongComparator c) {
		this(c);
		this.array = a;
		this.size = size;
	}
	
Wraps a given array in a queue using a given comparator.

The queue returned by this method will be backed by the given array.
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.
	 *
	 * @param a
	 *            an array.
	 * @param c
	 *            the comparator used in this queue, or {@code null} for the natural
	 *            order.
	 */
	public LongArrayPriorityQueue(final long[] a, final LongComparator 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.
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.
	 *
	 * @param a
	 *            an array.
	 * @param size
	 *            the number of elements to be included in the queue.
	 */
	public LongArrayPriorityQueue(final long[] 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.
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.
	 *
	 * @param a
	 *            an array.
	 */
	public LongArrayPriorityQueue(final long[] a) {
		this(a, a.length);
	}
	
Returns the index of the smallest element. /** Returns the index of the smallest element. */

	private int findFirst() {
		if (firstIndexValid)
			return this.firstIndex;
		firstIndexValid = true;
		int i = size;
		int firstIndex = --i;
		long first = array[firstIndex];
		if (c == null) {
			while (i-- != 0)
				if (((array[i]) < (first)))
					first = array[firstIndex = i];
		} else
			while (i-- != 0) {
				if (c.compare(array[i], first) < 0)
					first = array[firstIndex = i];
			}
		return this.firstIndex = firstIndex;
	}
	private void ensureNonEmpty() {
		if (size == 0)
			throw new NoSuchElementException();
	}
	@Override

	public void enqueue(long x) {
		if (size == array.length)
			array = LongArrays.grow(array, size + 1);
		if (firstIndexValid) {
			if (c == null) {
				if (((x) < (array[firstIndex])))
					firstIndex = size;
			} else if (c.compare(x, array[firstIndex]) < 0)
				firstIndex = size;
		} else
			firstIndexValid = false;
		array[size++] = x;
	}
	@Override
	public long dequeueLong() {
		ensureNonEmpty();
		final int first = findFirst();
		final long result = array[first];
		System.arraycopy(array, first + 1, array, first, --size - first);
		firstIndexValid = false;
		return result;
	}
	@Override
	public long firstLong() {
		ensureNonEmpty();
		return array[findFirst()];
	}
	@Override
	public void changed() {
		ensureNonEmpty();
		firstIndexValid = false;
	}
	@Override
	public int size() {
		return size;
	}
	@Override
	public void clear() {
		size = 0;
		firstIndexValid = false;
	}
	
Trims the underlying array so that it has exactly size() elements. /**
	 * Trims the underlying array so that it has exactly {@link #size()} elements.
	 */
	public void trim() {
		array = LongArrays.trim(array, size);
	}
	@Override
	public LongComparator comparator() {
		return c;
	}
	private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
		s.defaultWriteObject();
		s.writeInt(array.length);
		for (int i = 0; i < size; i++)
			s.writeLong(array[i]);
	}

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