Package it.unimi.dsi.fastutil

Interface IndirectPriorityQueue<K>

All Known Subinterfaces:
ByteIndirectPriorityQueue, CharIndirectPriorityQueue, DoubleIndirectPriorityQueue, FloatIndirectPriorityQueue, IntIndirectPriorityQueue, LongIndirectPriorityQueue, ShortIndirectPriorityQueue
All Known Implementing Classes:
AbstractIndirectPriorityQueue, ByteArrayIndirectPriorityQueue, ByteHeapIndirectPriorityQueue, ByteHeapSemiIndirectPriorityQueue, CharArrayIndirectPriorityQueue, CharHeapIndirectPriorityQueue, CharHeapSemiIndirectPriorityQueue, DoubleArrayIndirectPriorityQueue, DoubleHeapIndirectPriorityQueue, DoubleHeapSemiIndirectPriorityQueue, FloatArrayIndirectPriorityQueue, FloatHeapIndirectPriorityQueue, FloatHeapSemiIndirectPriorityQueue, IndirectPriorityQueues.EmptyIndirectPriorityQueue, IndirectPriorityQueues.SynchronizedIndirectPriorityQueue, IntArrayIndirectPriorityQueue, IntHeapIndirectPriorityQueue, IntHeapSemiIndirectPriorityQueue, LongArrayIndirectPriorityQueue, LongHeapIndirectPriorityQueue, LongHeapSemiIndirectPriorityQueue, ObjectArrayIndirectPriorityQueue, ObjectHeapIndirectPriorityQueue, ObjectHeapSemiIndirectPriorityQueue, ShortArrayIndirectPriorityQueue, ShortHeapIndirectPriorityQueue, ShortHeapSemiIndirectPriorityQueue
public interface IndirectPriorityQueue<K>
An indirect priority queue.

An indirect priority queue provides a way to enqueue by index elements taken from a given reference list, and to dequeue them in some specified order. Elements that are smaller in the specified order are dequeued first. It is also possible to get the index of the first element, that is, the index that would be dequeued next.

Additionally, the queue may provide a method to peek at the index of the element that would be dequeued last.

The reference list should not change during queue operations (or, more precisely, the relative order of the elements corresponding to indices in the queue should not change). Nonetheless, some implementations may give the caller a way to notify the queue that the first element has changed its relative position in the order.

Optionally, an indirect priority queue may even provide methods to notify the change of any element of the reference list, to check the presence of an index in the queue, and to remove an index from the queue. It may even allow to notify that all elements have changed.

It is always possible to enqueue two distinct indices corresponding to equal elements of the reference list. However, depending on the implementation, it may or may not be possible to enqueue twice the same index.

Note that all element manipulation happens via indices.

  • Method Summary

    Modifier and Type
    Method
    Description
    default void
    allChanged()
    Notifies this queue that the all elements have changed (optional operation).
    default void
    changed()
    Notifies this queue that the first element has changed (optional operation).
    default 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.
    default boolean
    contains(int index)
    Checks whether a given index belongs to this queue (optional operation).
    int
    dequeue()
    Dequeues the first element from this queue.
    void
    enqueue(int index)
    Enqueues a new element.
    int
    first()
    Returns the first element of this queue.
    default int
    front(int[] a)
    Retrieves the front of this queue in a given array (optional operation).
    default boolean
    isEmpty()
    Checks whether this queue is empty.
    default int
    last()
    Returns the last element of this queue, that is, the element the would be dequeued last (optional operation).
    default boolean
    remove(int index)
    Removes the specified element from this queue (optional operation).
    int
    size()
    Returns the number of elements in this queue.

  • Method Details

    • enqueue

      void enqueue(int index)
      Enqueues a new element.
      Parameters:
      index - the element to enqueue.

    • dequeue

      int dequeue()
      Dequeues the first element from this queue.
      Returns:
      the dequeued element.
      Throws:
      NoSuchElementException - if this queue is empty.

    • isEmpty

      default boolean isEmpty()
      Checks whether this queue is empty.

      This default implementation checks whether size() is zero.

      Returns:
      true if this queue is empty.

    • size

      int size()
      Returns the number of elements in this queue.
      Returns:
      the number of elements in this queue.

    • clear

      void clear()
      Removes all elements from this queue.

    • first

      int first()
      Returns the first element of this queue.
      Returns:
      the first element.
      Throws:
      NoSuchElementException - if this queue is empty.

    • last

      default int last()
      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.

      Returns:
      the last element.
      Throws:
      NoSuchElementException - if this queue is empty.

    • changed

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

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

    • comparator

      Comparator<? super K> comparator()
      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.

    • changed

      default 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.

      Parameters:
      index - the element that has changed.
      Throws:
      NoSuchElementException - if the specified element is not in this queue.

    • allChanged

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

      This default implementation just throws an UnsupportedOperationException.

    • contains

      default boolean contains(int index)
      Checks whether a given index belongs to this queue (optional operation).

      This default implementation just throws an UnsupportedOperationException.

      Parameters:
      index - an index possibly in the queue.
      Returns:
      true if the specified index belongs to this queue.

    • remove

      default boolean remove(int index)
      Removes the specified element from this queue (optional operation).

      This default implementation just throws an UnsupportedOperationException.

      Parameters:
      index - the element to be removed.
      Returns:
      true if the index was in the queue.

    • front

      default int front(int[] a)
      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.

      This default implementation just throws an UnsupportedOperationException.

      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).