src.it.unimi.dsi.fastutil.ints.IntArrayIndirectPriorityQueue 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 it.unimi.dsi.fastutil.ints.IntArrays;
import it.unimi.dsi.fastutil.AbstractIndirectPriorityQueue;
import java.util.NoSuchElementException;
/** A type-specific array-based semi-indirect priority queue.
*
* Instances of this class use as reference list a reference array,
* which must be provided to each constructor, and represent a priority queue
* using a backing array of integer indices—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. Moreover, it allows to enqueue several
* time the same index, without limitations.
*/
public class IntArrayIndirectPriorityQueue extends AbstractIndirectPriorityQueue implements IntIndirectPriorityQueue {
/** The reference array. */
protected int refArray[];
/** The backing array. */
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 without elements 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 null for the natural order.
*/
public IntArrayIndirectPriorityQueue( int[] refArray, int capacity, IntComparator c ) {
if ( capacity > 0 ) this.array = new int[ capacity ];
this.refArray = refArray;
this.c = c;
}
/** Creates a new empty queue with given capacity and using the natural order.
*
* @param refArray the reference array.
* @param capacity the initial capacity of this queue.
*/
public IntArrayIndirectPriorityQueue( int[] 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.
*
* @param refArray the reference array.
* @param c the comparator used in this queue, or null for the natural order.
*/
public IntArrayIndirectPriorityQueue( int[] refArray, IntComparator 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.
* @param refArray the reference array.
*/
public IntArrayIndirectPriorityQueue( int[] 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.
*
* @param refArray the reference array.
* @param a an array of indices into refArray.
* @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 IntArrayIndirectPriorityQueue( final int[] refArray, final int[] a, int size, final IntComparator c ) {
this( refArray, 0, 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 refArray the reference array.
* @param a an array of indices into refArray.
* @param c the comparator used in this queue, or null for the natural order.
*/
public IntArrayIndirectPriorityQueue( final int[] refArray, final int[] a, final IntComparator 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.
*
* @param refArray the reference array.
* @param a an array of indices into refArray.
* @param size the number of elements to be included in the queue.
*/
public IntArrayIndirectPriorityQueue( final int[] 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.
*
* @param refArray the reference array.
* @param a an array of indices into refArray.
*/
public IntArrayIndirectPriorityQueue( final int[] refArray, final int[] a ) {
this( refArray, a, a.length );
}
/** Returns the index (in {@link #array}) of the smallest element. */
@SuppressWarnings("unchecked")
private int findFirst() {
if ( firstIndexValid ) return this.firstIndex;
firstIndexValid = true;
int i = size;
int firstIndex = --i;
int first = refArray[ array[ firstIndex ] ];
if ( c == null ) while( i-- != 0 ) { if ( ( (refArray[ array[ i ] ]) < (first) ) ) first = refArray[ array[ firstIndex = i ] ]; }
else while( i-- != 0 ) { if ( c.compare( refArray[ array[ i ] ], first ) < 0 ) first = refArray[ array[ firstIndex = i ] ]; }
return this.firstIndex = firstIndex;
}
/** Returns the index (in {@link #array}) of the largest element. */
@SuppressWarnings("unchecked")
private int findLast() {
int i = size;
int lastIndex = --i;
int last = refArray[ array[ lastIndex ] ];
if ( c == null ) { while( i-- != 0 ) if ( ( (last) < (refArray[ array[ i ] ]) ) ) last = refArray[ array[ lastIndex = i ] ]; }
else { while( i-- != 0 ) if ( c.compare( last, refArray[ array[ i ] ] ) < 0 ) last = refArray[ array[ lastIndex = i ] ]; }
return lastIndex;
}
protected final void ensureNonEmpty() {
if ( size == 0 ) throw new NoSuchElementException();
}
/** Ensures that the given index is a firstIndexValid reference.
*
* @param index an index in the reference array.
* @throws IndexOutOfBoundsException if the given index is negative or larger than the reference array length.
*/
protected void ensureElement( final int index ) {
if ( index < 0 ) throw new IndexOutOfBoundsException( "Index (" + index + ") is negative" );
if ( index >= refArray.length ) throw new IndexOutOfBoundsException( "Index (" + index + ") is larger than or equal to reference array size (" + refArray.length + ")" );
}
/** Enqueues a new element.
*
*
Note that for efficiency reasons this method will not throw an exception
* when x is already in the queue. However, the queue state will become
* inconsistent and the following behaviour will not be predictable.
*/
@SuppressWarnings("unchecked")
public void enqueue( int x ) {
ensureElement( x );
if ( size == array.length ) array = IntArrays.grow( array, size + 1 );
if ( firstIndexValid ) {
if ( c == null ) { if ( ( (refArray[ x ]) < (refArray[ array[ firstIndex ] ]) ) ) firstIndex = size; }
else if ( c.compare( refArray[ x ], refArray[ array[ firstIndex ] ] ) < 0 ) firstIndex = size;
}
else firstIndexValid = false;
array[ size++ ] = x;
}
public int dequeue() {
ensureNonEmpty();
final int firstIndex = findFirst();
final int result = array[ firstIndex ];
if ( --size != 0 ) System.arraycopy( array, firstIndex + 1, array, firstIndex, size - firstIndex );
firstIndexValid = false;
return result;
}
public int first() {
ensureNonEmpty();
return array[ findFirst() ];
}
public int last() {
ensureNonEmpty();
return array[ findLast() ];
}
public void changed() {
ensureNonEmpty();
firstIndexValid = false;
}
/** {@inheritDoc}
*
*
Note that for efficiency reasons this method will not throw an exception
* when index is not in the queue.
*/
public void changed( int index ) {
ensureElement( index );
if ( index == firstIndex ) firstIndexValid = false;
}
public void allChanged() {
firstIndexValid = false;
}
public boolean remove( int index ) {
ensureElement( index );
final int[] a = array;
int i = size;
while( i-- != 0 ) if ( a[ i ] == index ) break;
if ( i < 0 ) return false;
firstIndexValid = false;
if ( --size != 0 ) System.arraycopy( a, i + 1, a, i, size - i );
return true;
}
public int front( int[] a ) {
final int top = refArray[ array[ findFirst() ] ];
int i = size, c = 0;
while( i-- != 0 ) if ( ( (top) == (refArray[ array[ i ] ]) ) ) a[ c++ ] = array[ i ];
return c;
}
public int size() { return size; }
public void clear() { size = 0; firstIndexValid = false; }
/** Trims the backing array so that it has exactly {@link #size()} elements.
*/
public void trim() {
array = IntArrays.trim( array, size );
}
public IntComparator comparator() { return c; }
public String toString() {
StringBuffer s = new StringBuffer();
s.append( "[" );
for ( int i = 0; i < size; i++ ) {
if ( i != 0 ) s.append( ", " );
s.append( refArray[ array [ i ] ] );
}
s.append( "]" );
return s.toString();
}
}