it.unimi.dsi.fastutil.longs

Class LongArrayIndirectPriorityQueue

java.lang.Object

it.unimi.dsi.fastutil.longs.LongArrayIndirectPriorityQueue

All Implemented Interfaces:

IndirectPriorityQueue<Long>, LongIndirectPriorityQueue

public class LongArrayIndirectPriorityQueue
extends Object
implements LongIndirectPriorityQueue

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 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.

Field Summary

Fields

Modifier and Type	Field and Description
protected int[]	array The backing array.
protected LongComparator	c The type-specific comparator used in this queue.
protected int	firstIndex The first index, cached, if firstIndexValid is true.
protected boolean	firstIndexValid Whether firstIndex contains a valid value.
protected long[]	refArray The reference array.
protected int	size The number of elements in this queue.

Constructor Summary

Constructors

Constructor and Description
LongArrayIndirectPriorityQueue(long[] refArray) Creates a new empty queue with capacity equal to the length of the reference array and using the natural order.
LongArrayIndirectPriorityQueue(long[] refArray, int capacity) Creates a new empty queue with given capacity and using the natural order.
LongArrayIndirectPriorityQueue(long[] refArray, int[] a) Wraps a given array in a queue using the natural order.
LongArrayIndirectPriorityQueue(long[] refArray, int[] a, int size) Wraps a given array in a queue using the natural order.
LongArrayIndirectPriorityQueue(long[] refArray, int[] a, int size, LongComparator c) Wraps a given array in a queue using a given comparator.
LongArrayIndirectPriorityQueue(long[] refArray, int[] a, LongComparator c) Wraps a given array in a queue using a given comparator.
LongArrayIndirectPriorityQueue(long[] refArray, int capacity, LongComparator c) Creates a new empty queue without elements with a given capacity and comparator.
LongArrayIndirectPriorityQueue(long[] refArray, LongComparator c) Creates a new empty queue with capacity equal to the length of the reference array and a given comparator.

Method Summary

Modifier and Type	Method and Description
void	allChanged() Signals the queue that all elements have changed.
void	changed() Notifies this queue that the first element has changed (optional operation).
void	changed(int index) Notifies this queue that the specified element has changed (optional operation).
void	clear() Removes all elements from this queue.
LongComparator	comparator() Returns the type-specific comparator associated with this queue.
int	dequeue() Dequeues the first element from this queue.
void	enqueue(int x) Enqueues a new element.
protected void	ensureElement(int index) Ensures that the given index is a firstIndexValid reference.
protected void	ensureNonEmpty()
int	first() Returns the first element of this queue.
int	front(int[] a) Writes in the provided array the front of the queue, that is, the set of indices whose elements have the same priority as the top.
int	last() Returns the last element of this queue, that is, the element the would be dequeued last (optional operation).
boolean	remove(int index) Removes the specified element from this queue (optional operation).
int	size() Returns the number of elements in this queue.
String	toString()
void	trim() Trims the backing array so that it has exactly size() elements.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface it.unimi.dsi.fastutil.IndirectPriorityQueue

contains, isEmpty

Field Detail

refArray

protected long[] refArray

The reference array.

array

protected int[] array

The backing array.

size

protected int size

The number of elements in this queue.

c

protected LongComparator c

The type-specific comparator used in this queue.

firstIndex

protected int firstIndex

The first index, cached, if firstIndexValid is true.

firstIndexValid

protected boolean firstIndexValid

Whether firstIndex contains a valid value.

Constructor Detail

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      int capacity,
                                      LongComparator c)

Creates a new empty queue without elements with a given capacity and comparator.

Parameters:

refArray - the reference array.

capacity - the initial capacity of this queue.

c - the comparator used in this queue, or null for the natural order.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      int capacity)

Creates a new empty queue with given capacity and using the natural order.

Parameters:

refArray - the reference array.

capacity - the initial capacity of this queue.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      LongComparator c)

Creates a new empty queue with capacity equal to the length of the reference array and a given comparator.

Parameters:

refArray - the reference array.

c - the comparator used in this queue, or null for the natural order.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray)

Creates a new empty queue with capacity equal to the length of the reference array and using the natural order.

Parameters:

refArray - the reference array.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      int[] a,
                                      int size,
                                      LongComparator 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.

Parameters:

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.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      int[] a,
                                      LongComparator 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.

Parameters:

refArray - the reference array.

a - an array of indices into refArray.

c - the comparator used in this queue, or null for the natural order.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      int[] a,
                                      int size)

Wraps a given array in a queue using the natural order.

The queue returned by this method will be backed by the given array.

Parameters:

refArray - the reference array.

a - an array of indices into refArray.

size - the number of elements to be included in the queue.

LongArrayIndirectPriorityQueue

public LongArrayIndirectPriorityQueue(long[] refArray,
                                      int[] a)

Wraps a given array in a queue using the natural order.

The queue returned by this method will be backed by the given array.

Parameters:

refArray - the reference array.

a - an array of indices into refArray.

Method Detail

ensureNonEmpty

protected final void ensureNonEmpty()

ensureElement

protected void ensureElement(int index)

Ensures that the given index is a firstIndexValid reference.

Parameters:

index - an index in the reference array.

Throws:

IndexOutOfBoundsException - if the given index is negative or larger than the reference array length.

enqueue

public void enqueue(int x)

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.

Specified by:

enqueue in interface IndirectPriorityQueue<Long>

Parameters:

x - the element to enqueue.

dequeue

public int dequeue()

Description copied from interface: IndirectPriorityQueue

Dequeues the first element from this queue.

Specified by:

dequeue in interface IndirectPriorityQueue<Long>

Returns:

the dequeued element.

first

public int first()

Description copied from interface: IndirectPriorityQueue

Returns the first element of this queue.

Specified by:

first in interface IndirectPriorityQueue<Long>

Returns:

the first element.

last

public int last()

Description copied from interface: IndirectPriorityQueue

Returns the last element of this queue, that is, the element the would be dequeued last (optional operation).

This default implementation just throws an UnsupportedOperationException.

Specified by:

last in interface IndirectPriorityQueue<Long>

Returns:

the last element.

changed

public void changed()

Description copied from interface: IndirectPriorityQueue

Notifies this queue that the first element has changed (optional operation).

This default implementation just calls IndirectPriorityQueue.changed(int) with argument IndirectPriorityQueue.first().

Specified by:

changed in interface IndirectPriorityQueue<Long>

changed

public void changed(int index)

Notifies this queue that the specified element has changed (optional operation).

Note that the specified element must belong to this queue.

This default implementation just throws an UnsupportedOperationException.

Note that for efficiency reasons this method will not throw an exception when index is not in the queue.

Specified by:

changed in interface IndirectPriorityQueue<Long>

Parameters:

index - the element that has changed.

allChanged

public void allChanged()

Signals the queue that all elements have changed.

Specified by:

allChanged in interface IndirectPriorityQueue<Long>

remove

public boolean remove(int index)

Description copied from interface: IndirectPriorityQueue

Removes the specified element from this queue (optional operation).

This default implementation just throws an UnsupportedOperationException.

Specified by:

remove in interface IndirectPriorityQueue<Long>

Parameters:

index - the element to be removed.

Returns:

true if the index was in the queue.

front

public int front(int[] a)

Writes in the provided array the front of the queue, that is, the set of indices whose elements have the same priority as the top.

Specified by:

front in interface IndirectPriorityQueue<Long>

Parameters:

a - an array whose initial part will be filled with the frnot (must be sized as least as the heap size).

Returns:

the number of elements of the front.

size

public int size()

Description copied from interface: IndirectPriorityQueue

Returns the number of elements in this queue.

Specified by:

size in interface IndirectPriorityQueue<Long>

Returns:

the number of elements in this queue.

clear

public void clear()

Description copied from interface: IndirectPriorityQueue

Removes all elements from this queue.

Specified by:

clear in interface IndirectPriorityQueue<Long>

trim

public void trim()

Trims the backing array so that it has exactly size() elements.

comparator

public LongComparator comparator()

Description copied from interface: LongIndirectPriorityQueue

Returns the type-specific comparator associated with this queue.

Note that this specification strengthens the one given in IndirectPriorityQueue.

Specified by:

comparator in interface IndirectPriorityQueue<Long>

Specified by:

comparator in interface LongIndirectPriorityQueue

Returns:

the comparator associated with this queue.

See Also:

IndirectPriorityQueue.comparator()

toString

public String toString()

Overrides:

toString in class Object