src.it.unimi.dsi.fastutil.ints.IntArrayPriorityQueue Maven / Gradle / Ivy
/* Generic definitions */
/* Assertions (useful to generate conditional code) */
/* Current type and class (and size, if applicable) */
/* Value methods */
/* Interfaces (keys) */
/* Interfaces (values) */
/* Abstract implementations (keys) */
/* Abstract implementations (values) */
/* Static containers (keys) */
/* Static containers (values) */
/* Implementations */
/* Synchronized wrappers */
/* Unmodifiable wrappers */
/* Other wrappers */
/* Methods (keys) */
/* Methods (values) */
/* Methods (keys/values) */
/* Methods that have special names depending on keys (but the special names depend on values) */
/* Equality */
/* Object/Reference-only definitions (keys) */
/* Primitive-type-only definitions (keys) */
/* Object/Reference-only definitions (values) */
/*
* Copyright (C) 2003-2013 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.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.
*
*
This implementation is extremely inefficient, but it is difficult to beat
* when the size of the queue is very small.
*/
public class IntArrayPriorityQueue extends AbstractIntPriorityQueue {
/** The backing array. */
@SuppressWarnings("unchecked")
protected int array[] = IntArrays.EMPTY_ARRAY;
/** The number of elements in this queue. */
protected int size;
/** The type-specific comparator used in this queue. */
protected IntComparator c;
/** The first index, cached, if {@link #firstIndexValid} is true. */
protected int firstIndex;
/** Whether {@link #firstIndex} contains a valid value. */
protected 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 null for the natural order.
*/
@SuppressWarnings("unchecked")
public IntArrayPriorityQueue( int capacity, IntComparator c ) {
if ( capacity > 0 ) this.array = new int[ 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 IntArrayPriorityQueue( int capacity ) {
this( capacity, null );
}
/** Creates a new empty queue with a given comparator.
*
* @param c the comparator used in this queue, or null for the natural order.
*/
public IntArrayPriorityQueue( IntComparator c ) {
this( 0, c );
}
/** Creates a new empty queue using the natural order.
*/
public IntArrayPriorityQueue() {
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 null for the natural order.
*/
public IntArrayPriorityQueue( final int[] a, int size, final IntComparator 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 null for the natural order.
*/
public IntArrayPriorityQueue( 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.
*
* @param a an array.
* @param size the number of elements to be included in the queue.
*/
public IntArrayPriorityQueue( 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.
*
* @param a an array.
*/
public IntArrayPriorityQueue( final int[] a ) {
this( a, a.length );
}
/** Returns the index of the smallest element. */
@SuppressWarnings("unchecked")
private int findFirst() {
if ( firstIndexValid ) return this.firstIndex;
firstIndexValid = true;
int i = size;
int firstIndex = --i;
int 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();
}
@SuppressWarnings("unchecked")
public void enqueue( int x ) {
if ( size == array.length ) array = IntArrays.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;
}
public int dequeueInt() {
ensureNonEmpty();
final int first = findFirst();
final int result = array[ first ];
System.arraycopy( array, first + 1, array, first, --size - first );
firstIndexValid = false;
return result;
}
public int firstInt() {
ensureNonEmpty();
return array[ findFirst() ];
}
public void changed() {
ensureNonEmpty();
firstIndexValid = false;
}
public int size() { return size; }
public void clear() {
size = 0;
firstIndexValid = false;
}
/** Trims the underlying array so that it has exactly {@link #size()} elements.
*/
public void trim() {
array = IntArrays.trim( array, size );
}
public IntComparator comparator() { return c; }
}