Package it.unimi.dsi.fastutil.objects

Class ObjectHeapSemiIndirectPriorityQueue<K>

java.lang.Object
it.unimi.dsi.fastutil.objects.ObjectHeapSemiIndirectPriorityQueue<K>
All Implemented Interfaces:
IndirectPriorityQueue<K>
Direct Known Subclasses:
ObjectHeapIndirectPriorityQueue
public class ObjectHeapSemiIndirectPriorityQueue<K> extends Object implements IndirectPriorityQueue<K>
A type-specific heap-based semi-indirect priority queue.

Instances of this class use as reference list a reference array, which must be provided to each constructor. The priority queue is represented using a heap. The heap is enlarged as needed, but it is never shrunk. Use the trim() method to reduce its size, if necessary.

Implementation Specification:
This implementation allows one to enqueue several time the same index, but you must be careful when calling changed().

  • Constructor Details

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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. The first size element of the array will be rearranged so to form a heap (this is more efficient than enqueing the elements of a one by one).

      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.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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. The elements of the array will be rearranged so to form a heap (this is more efficient than enqueing the elements of a one by one).

      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.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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. The first size element of the array will be rearranged so to form a heap (this is more efficient than enqueing the elements of a one by one).

      Parameters:
      refArray - the reference array.
      a - an array of indices into refArray.
      size - the number of elements to be included in the queue.

    • ObjectHeapSemiIndirectPriorityQueue

      public ObjectHeapSemiIndirectPriorityQueue(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. The elements of the array will be rearranged so to form a heap (this is more efficient than enqueing the elements of a one by one).

      Parameters:
      refArray - the reference array.
      a - an array of indices into refArray.

  • Method Details

    • enqueue

      public void enqueue(int x)
      Description copied from interface: IndirectPriorityQueue
      Enqueues a new element.
      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.

    • changed

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

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

      The caller must guarantee that when this method is called the index of the first element appears just once in the queue. Failure to do so will bring the queue in an inconsistent state, and will cause unpredictable behaviour.

      Specified by:
      changed in interface IndirectPriorityQueue<K>

    • allChanged

      public void allChanged()
      Rebuilds this heap in a bottom-up fashion (in linear time).
      Specified by:
      allChanged in interface IndirectPriorityQueue<K>

    • 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.

    • 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.

    • toString

      public String toString()
      Overrides:
      toString in class Object