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/*
* Copyright (C) 2003-2022 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 PACKAGE;
#if KEY_CLASS_Object
import java.util.Arrays;
import java.util.Comparator;
import it.unimi.dsi.fastutil.PriorityQueue;
#endif
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 {@link #trim()} method
* to reduce its size, if necessary.
*
* @implSpec This implementation is extremely inefficient, but it is difficult to beat
* when the size of the queue is very small.
*/
public class ARRAY_PRIORITY_QUEUE KEY_GENERIC implements PRIORITY_QUEUE KEY_GENERIC, java.io.Serializable {
private static final long serialVersionUID = 1L;
/** The backing array. */
SUPPRESS_WARNINGS_KEY_UNCHECKED
protected transient KEY_GENERIC_TYPE array[] = KEY_GENERIC_ARRAY_CAST ARRAYS.EMPTY_ARRAY;
/** The number of elements in this queue. */
protected int size;
/** The type-specific comparator used in this queue. */
protected KEY_COMPARATOR KEY_SUPER_GENERIC c;
/** The first index, cached, if {@link #firstIndexValid} is true. */
protected transient int firstIndex;
/** Whether {@link #firstIndex} contains a valid value. */
protected transient boolean firstIndexValid;
/** 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.
*/
SUPPRESS_WARNINGS_KEY_UNCHECKED
public ARRAY_PRIORITY_QUEUE(int capacity, KEY_COMPARATOR KEY_SUPER_GENERIC c) {
if (capacity > 0) this.array = KEY_GENERIC_ARRAY_CAST new KEY_TYPE[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 ARRAY_PRIORITY_QUEUE(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 ARRAY_PRIORITY_QUEUE(KEY_COMPARATOR KEY_SUPER_GENERIC c) {
this(0, c);
}
/** Creates a new empty queue using the natural order.
*/
public ARRAY_PRIORITY_QUEUE() {
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.
*
* @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 ARRAY_PRIORITY_QUEUE(final KEY_GENERIC_TYPE[] a, int size, final KEY_COMPARATOR KEY_SUPER_GENERIC 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.
*
* @param a an array.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public ARRAY_PRIORITY_QUEUE(final KEY_GENERIC_TYPE[] a, final KEY_COMPARATOR KEY_SUPER_GENERIC 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.
*
* @param a an array.
* @param size the number of elements to be included in the queue.
*/
public ARRAY_PRIORITY_QUEUE(final KEY_GENERIC_TYPE[] 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.
*
* @param a an array.
*/
public ARRAY_PRIORITY_QUEUE(final KEY_GENERIC_TYPE[] a) {
this(a, a.length);
}
/** Returns the index of the smallest element. */
SUPPRESS_WARNINGS_KEY_UNCHECKED
private int findFirst() {
if (firstIndexValid) return this.firstIndex;
firstIndexValid = true;
int i = size;
int firstIndex = --i;
KEY_GENERIC_TYPE first = array[firstIndex];
if (c == null) { while(i-- != 0) if (KEY_LESS(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
SUPPRESS_WARNINGS_KEY_UNCHECKED
public void enqueue(KEY_GENERIC_TYPE x) {
if (size == array.length) array = ARRAYS.grow(array, size + 1);
if (firstIndexValid) {
if (c == null) { if (KEY_LESS(x, array[firstIndex])) firstIndex = size; }
else if (c.compare(x, array[firstIndex]) < 0) firstIndex = size;
}
else firstIndexValid = false;
array[size++] = x;
}
@Override
public KEY_GENERIC_TYPE DEQUEUE() {
ensureNonEmpty();
final int first = findFirst();
final KEY_GENERIC_TYPE result = array[first];
System.arraycopy(array, first + 1, array, first, --size - first);
#if KEY_CLASS_Object
array[size] = null;
#endif
firstIndexValid = false;
return result;
}
@Override
public KEY_GENERIC_TYPE FIRST() {
ensureNonEmpty();
return array[findFirst()];
}
@Override
public void changed() {
ensureNonEmpty();
firstIndexValid = false;
}
@Override
public int size() { return size; }
@Override
public void clear() {
#if KEY_CLASS_Object
Arrays.fill(array, 0, size, null);
#endif
size = 0;
firstIndexValid = false;
}
/** Trims the underlying array so that it has exactly {@link #size()} elements. */
public void trim() {
array = ARRAYS.trim(array, size);
}
@Override
public KEY_COMPARATOR KEY_SUPER_GENERIC 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.WRITE_KEY(array[i]);
}
SUPPRESS_WARNINGS_KEY_UNCHECKED
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
array = KEY_GENERIC_ARRAY_CAST new KEY_TYPE[s.readInt()];
for(int i = 0; i < size; i++) array[i] = KEY_GENERIC_CAST s.READ_KEY();
}
}