it.unimi.dsi.fastutil.ints

Class IntArrayIndirectPriorityQueue

java.lang.Object

it.unimi.dsi.fastutil.AbstractIndirectPriorityQueue<Integer>

it.unimi.dsi.fastutil.ints.IntArrayIndirectPriorityQueue

All Implemented Interfaces:

IndirectPriorityQueue<Integer>

public class IntArrayIndirectPriorityQueue
extends AbstractIndirectPriorityQueue<Integer>

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 IntComparator	c The type-specific comparator used in this queue.
protected int[]	refArray The reference array.
protected int	size The number of elements in this queue.

Constructor Summary

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
void	allChanged() Notifies this queue that the all elements have changed (optional operation).
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.
IntComparator	comparator() Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
int	dequeue() Dequeues an element.
void	enqueue(int x) Enqueues a new element.
protected void	ensureElement(int index) Ensures that the given index is a valid reference.
protected void	ensureNonEmpty()
int	first() Returns the first element of this queue.
int	front(int[] a) Retrieves the front of this queue in a given array (optional operation).
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 it.unimi.dsi.fastutil.AbstractIndirectPriorityQueue

contains, isEmpty

Methods inherited from class java.lang.Object

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

Field Detail

refArray

protected int[] refArray

The reference array.

array

protected int[] array

The backing array.

size

protected int size

The number of elements in this queue.

c

protected IntComparator c

The type-specific comparator used in this queue.

Constructor Detail

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] refArray,
                             int capacity,
                             IntComparator 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] refArray,
                             IntComparator 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] refArray,
                             int[] a,
                             int size,
                             IntComparator 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] refArray,
                             int[] a,
                             IntComparator 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] 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.

IntArrayIndirectPriorityQueue

public IntArrayIndirectPriorityQueue(int[] 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 valid 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.

Parameters:

x - the element to enqueue..

dequeue

public int dequeue()

Dequeues an element.

Note that each call to this method requires a complete scan of the backing array. Please consider caching its result.

Returns:

the dequeued element.

first

public int first()

Description copied from interface: IndirectPriorityQueue

Returns the first element of this queue.

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).

Specified by:

last in interface IndirectPriorityQueue<Integer>

Overrides:

last in class AbstractIndirectPriorityQueue<Integer>

Returns:

the last element.

changed

public void changed()

Description copied from interface: IndirectPriorityQueue

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

Specified by:

changed in interface IndirectPriorityQueue<Integer>

Overrides:

changed in class AbstractIndirectPriorityQueue<Integer>

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.

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<Integer>

Overrides:

changed in class AbstractIndirectPriorityQueue<Integer>

Parameters:

index - the element that has changed.

allChanged

public void allChanged()

Description copied from interface: IndirectPriorityQueue

Notifies this queue that the all elements have changed (optional operation).

Specified by:

allChanged in interface IndirectPriorityQueue<Integer>

Overrides:

allChanged in class AbstractIndirectPriorityQueue<Integer>

remove

public boolean remove(int index)

Description copied from interface: IndirectPriorityQueue

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

Specified by:

remove in interface IndirectPriorityQueue<Integer>

Overrides:

remove in class AbstractIndirectPriorityQueue<Integer>

Parameters:

index - the element to be removed.

Returns:

true if the index was in the queue.

front

public int front(int[] a)

Description copied from interface: IndirectPriorityQueue

Retrieves the front of this queue in a given array (optional operation).

The front of an indirect queue is the set of indices whose associated elements in the reference array are equal to the element associated to the first index. These indices can be always obtain by dequeueing, but this method should retrieve efficiently such indices in the given array without modifying the state of this queue.

Parameters:

a - an array large enough to hold the front (e.g., at least long as the reference array).

Returns:

the number of elements actually written (starting from the first position of a).

size

public int size()

Description copied from interface: IndirectPriorityQueue

Returns the number of elements in this queue.

Returns:

the number of elements in this queue.

clear

public void clear()

Description copied from interface: IndirectPriorityQueue

Removes all elements from this queue.

trim

public void trim()

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

comparator

public IntComparator comparator()

Description copied from interface: IndirectPriorityQueue

Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.

Returns:

the comparator associated with this sorted set, or null if it uses its elements' natural ordering.

toString

public String toString()

Overrides:

toString in class Object