/*
	* 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.shorts;
import it.unimi.dsi.fastutil.ints.IntArrays;
import java.util.Arrays;
import java.util.NoSuchElementException;
A type-specific heap-based indirect priority queue.

Instances of this class use an additional inversion array, of the same length of the reference array, to keep track of the heap position containing a given element of the reference array. The priority queue is represented using a heap. The heap is enlarged as needed, but it is never shrunk. Use the ShortHeapSemiIndirectPriorityQueue.trim() method to reduce its size, if necessary. 

This implementation does not allow one to enqueue several times the
same index.
/**
 * A type-specific heap-based indirect priority queue.
 *
 * <p>
 * Instances of this class use an additional <em>inversion array</em>, of the
 * same length of the reference array, to keep track of the heap position
 * containing a given element of the reference array. The priority queue is
 * represented 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.
 *
 * <p>
 * This implementation does <em>not</em> allow one to enqueue several times the
 * same index.
 */
public class ShortHeapIndirectPriorityQueue extends ShortHeapSemiIndirectPriorityQueue {
	
The inversion array. /** The inversion array. */
	protected final int inv[];
	
Creates a new empty queue with a given capacity and comparator.
Params:
refArray – 
           the reference array.
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 refArray
	 *            the reference array.
	 * @param capacity
	 *            the initial capacity of this queue.
	 * @param c
	 *            the comparator used in this queue, or {@code null} for the natural
	 *            order.
	 */
	public ShortHeapIndirectPriorityQueue(short[] refArray, int capacity, ShortComparator c) {
		super(refArray, capacity, c);
		if (capacity > 0)
			this.heap = new int[capacity];
		this.c = c;
		this.inv = new int[refArray.length];
		Arrays.fill(inv, -1);
	}
	
Creates a new empty queue with a given capacity and using the natural order.
Params:
refArray – 
           the reference array.
capacity – 
           the initial capacity of this queue./**
	 * Creates a new empty queue with a given capacity and using the natural order.
	 *
	 * @param refArray
	 *            the reference array.
	 * @param capacity
	 *            the initial capacity of this queue.
	 */
	public ShortHeapIndirectPriorityQueue(short[] refArray, int capacity) {
		this(refArray, capacity, null);
	}
	
Creates a new empty queue with capacity equal to the length of the reference
array and a given comparator.
Params:
refArray – 
           the reference array.
c –  the comparator used in this queue, or null for the natural order./**
	 * Creates a new empty queue with capacity equal to the length of the reference
	 * array and a given comparator.
	 *
	 * @param refArray
	 *            the reference array.
	 * @param c
	 *            the comparator used in this queue, or {@code null} for the natural
	 *            order.
	 */
	public ShortHeapIndirectPriorityQueue(short[] refArray, ShortComparator c) {
		this(refArray, refArray.length, c);
	}
	
Creates a new empty queue with capacity equal to the length of the reference
array and using the natural order.
Params:
refArray – 
           the reference array./**
	 * Creates a new empty queue with capacity equal to the length of the reference
	 * array and using the natural order.
	 * 
	 * @param refArray
	 *            the reference array.
	 */
	public ShortHeapIndirectPriorityQueue(short[] refArray) {
		this(refArray, refArray.length, 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:
refArray – 
           the reference array.
a –  an array of indices into refArray.
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 refArray
	 *            the reference array.
	 * @param a
	 *            an array of indices into {@code refArray}.
	 * @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 ShortHeapIndirectPriorityQueue(final short[] refArray, final int[] a, final int size,
			final ShortComparator c) {
		this(refArray, 0, c);
		this.heap = a;
		this.size = size;
		int i = size;
		while (i-- != 0) {
			if (inv[a[i]] != -1)
				throw new IllegalArgumentException("Index " + a[i] + " appears twice in the heap");
			inv[a[i]] = i;
		}
		ShortIndirectHeaps.makeHeap(refArray, a, inv, 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:
refArray – 
           the reference array.
a –  an array of indices into refArray.
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 refArray
	 *            the reference array.
	 * @param a
	 *            an array of indices into {@code refArray}.
	 * @param c
	 *            the comparator used in this queue, or {@code null} for the natural
	 *            order.
	 */
	public ShortHeapIndirectPriorityQueue(final short[] refArray, final int[] a, final ShortComparator c) {
		this(refArray, 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:
refArray – 
           the reference array.
a –  an array of indices into refArray.
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 refArray
	 *            the reference array.
	 * @param a
	 *            an array of indices into {@code refArray}.
	 * @param size
	 *            the number of elements to be included in the queue.
	 */
	public ShortHeapIndirectPriorityQueue(final short[] refArray, final int[] a, int size) {
		this(refArray, 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:
refArray – 
           the reference array.
a –  an array of indices into refArray./**
	 * 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 refArray
	 *            the reference array.
	 * @param a
	 *            an array of indices into {@code refArray}.
	 */
	public ShortHeapIndirectPriorityQueue(final short[] refArray, final int[] a) {
		this(refArray, a, a.length);
	}
	@Override
	public void enqueue(final int x) {
		if (inv[x] >= 0)
			throw new IllegalArgumentException("Index " + x + " belongs to the queue");
		if (size == heap.length)
			heap = IntArrays.grow(heap, size + 1);
		inv[heap[size] = x] = size++;
		ShortIndirectHeaps.upHeap(refArray, heap, inv, size, size - 1, c);
	}
	@Override
	public boolean contains(final int index) {
		return inv[index] >= 0;
	}
	@Override
	public int dequeue() {
		if (size == 0)
			throw new NoSuchElementException();
		final int result = heap[0];
		if (--size != 0)
			inv[heap[0] = heap[size]] = 0;
		inv[result] = -1;
		if (size != 0)
			ShortIndirectHeaps.downHeap(refArray, heap, inv, size, 0, c);
		return result;
	}
	@Override
	public void changed() {
		ShortIndirectHeaps.downHeap(refArray, heap, inv, size, 0, c);
	}
	@Override
	public void changed(final int index) {
		final int pos = inv[index];
		if (pos < 0)
			throw new IllegalArgumentException("Index " + index + " does not belong to the queue");
		final int newPos = ShortIndirectHeaps.upHeap(refArray, heap, inv, size, pos, c);
		ShortIndirectHeaps.downHeap(refArray, heap, inv, size, newPos, c);
	}
	
Rebuilds this queue in a bottom-up fashion (in linear time). /** Rebuilds this queue in a bottom-up fashion (in linear time). */
	@Override
	public void allChanged() {
		ShortIndirectHeaps.makeHeap(refArray, heap, inv, size, c);
	}
	@Override
	public boolean remove(final int index) {
		final int result = inv[index];
		if (result < 0)
			return false;
		inv[index] = -1;
		if (result < --size) {
			inv[heap[result] = heap[size]] = result;
			final int newPos = ShortIndirectHeaps.upHeap(refArray, heap, inv, size, result, c);
			ShortIndirectHeaps.downHeap(refArray, heap, inv, size, newPos, c);
		}
		return true;
	}
	@Override
	public void clear() {
		size = 0;
		Arrays.fill(inv, -1);
	}
}