it.unimi.dsi.fastutil.doubles

Class DoubleArrayPriorityQueue

java.lang.Object

it.unimi.dsi.fastutil.AbstractPriorityQueue<Double>

it.unimi.dsi.fastutil.doubles.AbstractDoublePriorityQueue

it.unimi.dsi.fastutil.doubles.DoubleArrayPriorityQueue

All Implemented Interfaces:

DoublePriorityQueue, PriorityQueue<Double>

public class DoubleArrayPriorityQueue
extends AbstractDoublePriorityQueue

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 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.

Field Summary

Fields

Modifier and Type	Field and Description
protected double[]	array The backing array.
protected DoubleComparator	c The type-specific comparator used in this queue.
protected int	size The number of elements in this queue.

Constructor Summary

Constructors

Constructor and Description
DoubleArrayPriorityQueue() Creates a new empty queue using the natural order.
DoubleArrayPriorityQueue(double[] a) Wraps a given array in a queue using the natural order.
DoubleArrayPriorityQueue(double[] a, DoubleComparator c) Wraps a given array in a queue using a given comparator.
DoubleArrayPriorityQueue(double[] a, int size) Wraps a given array in a queue using the natural order.
DoubleArrayPriorityQueue(double[] a, int size, DoubleComparator c) Wraps a given array in a queue using a given comparator.
DoubleArrayPriorityQueue(DoubleComparator c) Creates a new empty queue with a given comparator.
DoubleArrayPriorityQueue(int capacity) Creates a new empty queue with a given capacity and using the natural order.
DoubleArrayPriorityQueue(int capacity, DoubleComparator c) Creates a new empty queue with a given capacity and comparator.

Method Summary

Methods

Modifier and Type	Method and Description
void	changed() Notifies the queue that the first element has changed (optional operation).
void	clear() Removes all elements from this queue.
DoubleComparator	comparator() Returns the comparator associated with this sorted set, or null if it uses its elements' natural ordering.
double	dequeueDouble() Dequeues an element.
void	enqueue(double x) Enqueues a new element.
double	firstDouble() Returns the first element of the queue.
int	size() Returns the number of elements in this queue.
void	trim() Trims the underlying array so that it has exactly size() elements.

Methods inherited from class it.unimi.dsi.fastutil.doubles.AbstractDoublePriorityQueue

dequeue, enqueue, first, last, lastDouble

Methods inherited from class it.unimi.dsi.fastutil.AbstractPriorityQueue

isEmpty

Methods inherited from class java.lang.Object

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

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

isEmpty

Field Detail

array

protected double[] array

The backing array.

size

protected int size

The number of elements in this queue.

c

protected DoubleComparator c

The type-specific comparator used in this queue.

Constructor Detail

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(int capacity,
                        DoubleComparator c)

Creates a new empty queue with a given capacity and comparator.

Parameters:

capacity - the initial capacity of this queue.

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

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(int capacity)

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

Parameters:

capacity - the initial capacity of this queue.

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(DoubleComparator c)

Creates a new empty queue with a given comparator.

Parameters:

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

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue()

Creates a new empty queue using the natural order.

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(double[] a,
                        int size,
                        DoubleComparator 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:

a - an array.

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

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

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(double[] a,
                        DoubleComparator 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:

a - an array.

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

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(double[] 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:

a - an array.

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

DoubleArrayPriorityQueue

public DoubleArrayPriorityQueue(double[] 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:

a - an array.

Method Detail

enqueue

public void enqueue(double x)

Description copied from interface: DoublePriorityQueue

Enqueues a new element.

Parameters:

x - the element to enqueue.

dequeueDouble

public double dequeueDouble()

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.

firstDouble

public double firstDouble()

Description copied from interface: DoublePriorityQueue

Returns the first element of the queue.

Returns:

the first element.

changed

public void changed()

Description copied from interface: PriorityQueue

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

Specified by:

changed in interface PriorityQueue<Double>

Overrides:

changed in class AbstractPriorityQueue<Double>

size

public int size()

Description copied from interface: PriorityQueue

Returns the number of elements in this queue.

Returns:

the number of elements in this queue.

clear

public void clear()

Description copied from interface: PriorityQueue

Removes all elements from this queue.

trim

public void trim()

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

comparator

public DoubleComparator comparator()

Description copied from interface: DoublePriorityQueue

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

Note that this specification strengthens the one given in PriorityQueue.comparator().

Returns:

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

See Also:

PriorityQueue.comparator()