it.unimi.dsi.fastutil.doubles
Class DoubleArrayIndirectPriorityQueue

java.lang.Object
  extended by it.unimi.dsi.fastutil.AbstractIndirectPriorityQueue<java.lang.Double>
      extended by it.unimi.dsi.fastutil.doubles.DoubleArrayIndirectPriorityQueue
All Implemented Interfaces:
IndirectPriorityQueue<java.lang.Double>
Direct Known Subclasses:
DoubleArrayIndirectDoublePriorityQueue

public class DoubleArrayIndirectPriorityQueue
extends AbstractIndirectPriorityQueue<java.lang.Double>

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.


Constructor Summary
DoubleArrayIndirectPriorityQueue(double[] refArray)
          Creates a new empty queue with capacity equal to the length of the reference array and using the natural order.
DoubleArrayIndirectPriorityQueue(double[] refArray, DoubleComparator c)
          Creates a new empty queue with capacity equal to the length of the reference array and a given comparator.
DoubleArrayIndirectPriorityQueue(double[] refArray, int capacity)
          Creates a new empty queue with given capacity and using the natural order.
DoubleArrayIndirectPriorityQueue(double[] refArray, int[] a)
          Wraps a given array in a queue using the natural order.
DoubleArrayIndirectPriorityQueue(double[] refArray, int[] a, DoubleComparator c)
          Wraps a given array in a queue using a given comparator.
DoubleArrayIndirectPriorityQueue(double[] refArray, int[] a, int size)
          Wraps a given array in a queue using the natural order.
DoubleArrayIndirectPriorityQueue(double[] refArray, int[] a, int size, DoubleComparator c)
          Wraps a given array in a queue using a given comparator.
DoubleArrayIndirectPriorityQueue(double[] refArray, int capacity, DoubleComparator c)
          Creates a new empty queue without elements with a given capacity and comparator.
 
Method Summary
 void allChanged()
          Notifies the queue that the all elements have changed (optional operation).
 void changed()
          Notifies the queue that the first element has changed (optional operation).
 void changed(int index)
          Notifies the queue that the specified element has changed (optional operation). Note that for efficiency reasons this method will not throw an exception when index is not in the queue.
 void clear()
          Removes all elements from this queue.
 DoubleComparator 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.
 int first()
          Returns the first element of the queue.
 int front(int[] a)
          Retrieves the front of the queue in a given array (optional operation).
 int last()
          Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).
 void remove(int index)
          Removes the specified element from the queue (optional operation).
 int size()
          Returns the number of elements in this queue.
 java.lang.String toString()
           
 void trim()
          Trims the backing array so that it has exactly size() elements.
 
Methods inherited from class it.unimi.dsi.fastutil.AbstractIndirectPriorityQueue
isEmpty
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] refArray,
                                        int capacity,
                                        DoubleComparator 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.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] 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.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] refArray,
                                        DoubleComparator 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.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] 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.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] refArray,
                                        int[] 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:
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.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] refArray,
                                        int[] 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:
refArray - the reference array.
a - an array of indices into refArray.
c - the comparator used in this queue, or null for the natural order.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] 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.

DoubleArrayIndirectPriorityQueue

public DoubleArrayIndirectPriorityQueue(double[] 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

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 the queue.

Returns:
the first element.

last

public int last()
Description copied from interface: IndirectPriorityQueue
Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).

Specified by:
last in interface IndirectPriorityQueue<java.lang.Double>
Overrides:
last in class AbstractIndirectPriorityQueue<java.lang.Double>
Returns:
the last element.

changed

public void changed()
Description copied from interface: IndirectPriorityQueue
Notifies the queue that the first element has changed (optional operation).

Specified by:
changed in interface IndirectPriorityQueue<java.lang.Double>
Overrides:
changed in class AbstractIndirectPriorityQueue<java.lang.Double>

changed

public void changed(int index)
Notifies the queue that the specified element has changed (optional operation).

Note that the specified element must belong to the 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<java.lang.Double>
Overrides:
changed in class AbstractIndirectPriorityQueue<java.lang.Double>
Parameters:
index - the element that has changed.

allChanged

public void allChanged()
Description copied from interface: IndirectPriorityQueue
Notifies the queue that the all elements have changed (optional operation).

Specified by:
allChanged in interface IndirectPriorityQueue<java.lang.Double>
Overrides:
allChanged in class AbstractIndirectPriorityQueue<java.lang.Double>

remove

public void remove(int index)
Description copied from interface: IndirectPriorityQueue
Removes the specified element from the queue (optional operation).

Note that the specified element must belong to the queue.

Specified by:
remove in interface IndirectPriorityQueue<java.lang.Double>
Overrides:
remove in class AbstractIndirectPriorityQueue<java.lang.Double>
Parameters:
index - the element to be removed.

front

public int front(int[] a)
Description copied from interface: IndirectPriorityQueue
Retrieves the front of the 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 the 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 DoubleComparator 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 java.lang.String toString()
Overrides:
toString in class java.lang.Object