Package it.unimi.dsi.fastutil.objects

Class ObjectArrayIndirectPriorityQueue<K>

java.lang.Object
it.unimi.dsi.fastutil.objects.ObjectArrayIndirectPriorityQueue<K>
All Implemented Interfaces:
IndirectPriorityQueue<K>
public class ObjectArrayIndirectPriorityQueue<K> extends Object implements IndirectPriorityQueue<K>
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.

Implementation Specification:
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

    Constructors
    Constructor
    Description
    ObjectArrayIndirectPriorityQueue(K[] refArray)
    Creates a new empty queue with capacity equal to the length of the reference array and using the natural order.
    ObjectArrayIndirectPriorityQueue(K[] refArray, int capacity)
    Creates a new empty queue with given capacity and using the natural order.
    ObjectArrayIndirectPriorityQueue(K[] refArray, int[] a)
    Wraps a given array in a queue using the natural order.
    ObjectArrayIndirectPriorityQueue(K[] refArray, int[] a, int size)
    Wraps a given array in a queue using the natural order.
    ObjectArrayIndirectPriorityQueue(K[] refArray, int[] a, int size, Comparator<? super K> c)
    Wraps a given array in a queue using a given comparator.
    ObjectArrayIndirectPriorityQueue(K[] refArray, int[] a, Comparator<? super K> c)
    Wraps a given array in a queue using a given comparator.
    ObjectArrayIndirectPriorityQueue(K[] refArray, int capacity, Comparator<? super K> c)
    Creates a new empty queue without elements with a given capacity and comparator.
    ObjectArrayIndirectPriorityQueue(K[] refArray, Comparator<? super K> 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
    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.
    Comparator<? super K>
    comparator()
    Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
    int
    dequeue()
    Dequeues the first element from this queue.
    void
    enqueue(int x)
    Enqueues a new element.
    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

    equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

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

    contains, isEmpty

  • Constructor Details

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] refArray, int capacity, Comparator<? super K> 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] refArray, Comparator<? super K> 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] refArray, int[] a, int size, Comparator<? super K> 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] refArray, int[] a, Comparator<? super K> 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] 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.

    • ObjectArrayIndirectPriorityQueue

      public ObjectArrayIndirectPriorityQueue(K[] 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 Details

    • 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<K>
      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<K>
      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<K>
      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<K>
      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<K>

    • 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<K>
      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<K>

    • 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<K>
      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<K>
      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<K>
      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<K>

    • trim

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

    • comparator

      public Comparator<? super K> comparator()
      Description copied from interface: IndirectPriorityQueue
      Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
      Specified by:
      comparator in interface IndirectPriorityQueue<K>
      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