it.unimi.dsi.fastutil.chars.CharHeapPriorityQueue Maven / Gradle / Ivy
/*
* Copyright (C) 2003-2017 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.chars;
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 CharHeapPriorityQueue extends AbstractCharPriorityQueue implements java.io.Serializable {
private static final long serialVersionUID = 1L;
/** The heap array. */
protected transient char[] heap = CharArrays.EMPTY_ARRAY;
/** The number of elements in this queue. */
protected int size;
/** The type-specific comparator used in this queue. */
protected CharComparator 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 CharHeapPriorityQueue(int capacity, CharComparator c) {
if (capacity > 0) this.heap = new char[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 CharHeapPriorityQueue(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 CharHeapPriorityQueue(CharComparator c) {
this(0, c);
}
/** Creates a new empty queue using the natural order.
*/
public CharHeapPriorityQueue() {
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).
*
* @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 CharHeapPriorityQueue(final char[] a, int size, final CharComparator c) {
this(c);
this.heap = a;
this.size = size;
CharHeaps.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).
*
* @param a an array.
* @param c the comparator used in this queue, or {@code null} for the natural order.
*/
public CharHeapPriorityQueue(final char[] a, final CharComparator 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).
*
* @param a an array.
* @param size the number of elements to be included in the queue.
*/
public CharHeapPriorityQueue(final char[] 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).
*
* @param a an array.
*/
public CharHeapPriorityQueue(final char[] 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.
*
* @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 CharHeapPriorityQueue(final CharCollection collection, final CharComparator c) {
this(collection.toCharArray(), 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.
*
* @param collection a collection; its elements will be used to initialize the queue.
*/
public CharHeapPriorityQueue(final CharCollection 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.
*
* @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 CharHeapPriorityQueue(final Collection collection, final CharComparator c) {
this(collection.size(), c);
final Iterator iterator = collection.iterator();
final int size = collection.size();
for(int i = 0 ; i < size; i++) heap[i] = ((((Character)(iterator.next())).charValue()));
}
/** 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.
*
* @param collection a collection; its elements will be used to initialize the queue.
*/
public CharHeapPriorityQueue(final Collection collection) {
this(collection, null);
}
@Override
public void enqueue(char x) {
if (size == heap.length) heap = CharArrays.grow(heap, size + 1);
heap[size++] = x;
CharHeaps.upHeap(heap, size, size - 1, c);
}
@Override
public char dequeueChar() {
if (size == 0) throw new NoSuchElementException();
final char result = heap[0];
heap[0] = heap[--size];
if (size != 0) CharHeaps.downHeap(heap, size, 0, c);
return result;
}
@Override
public char firstChar() {
if (size == 0) throw new NoSuchElementException();
return heap[0];
}
@Override
public void changed() {
CharHeaps.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 = CharArrays.trim(heap, size);
}
@Override
public CharComparator 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.writeChar(heap[i]);
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
heap = new char[s.readInt()];
for(int i = 0; i < size; i++) heap[i] = s.readChar();
}
}