Class PriorityQueue<T>

A PriorityQueue<T> holds elements on a priority heap, which orders the elements according to their natural order or according to the comparator specified at construction time. If the queue uses natural ordering, only elements that are comparable are permitted to be inserted into the queue.

The least element of the specified ordering is stored at the head of the queue and the greatest element is stored at the tail of the queue.

A PriorityQueue<T> is not synchronized.

Inheritance

System.Object

PriorityQueue<T>

Implements

System.Collections.Generic.ICollection<T>

System.Collections.Generic.IEnumerable<T>

System.Collections.IEnumerable

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: Lucene.Net.Support

Assembly: Lucene.Net.dll

Syntax

public class PriorityQueue<T> : ICollection<T>, IEnumerable<T>, IEnumerable where T : class

Type Parameters

Name	Description
T	Type of elements

Constructors

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PriorityQueue()

Constructs a priority queue with an initial capacity of 11 and natural ordering.

Declaration

public PriorityQueue()

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PriorityQueue(PriorityQueue<T>)

Creates a PriorityQueue<T> containing the elements in the specified priority queue. This priority queue will be ordered according to the same ordering as the given priority queue.

Declaration

public PriorityQueue(PriorityQueue<T> collection)

Parameters

Type	Name	Description
PriorityQueue<T>	collection	the priority queue whose elements are to be placed into this priority queue

Exceptions

Type	Condition
System.InvalidCastException	if elements of `collection` cannot be compared to one another according to `collection`'s ordering

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PriorityQueue(TreeSet<T>)

Creates a PriorityQueue<T> containing the elements in the specified TreeSet<T>. This priority queue will be ordered according to the same ordering as the given TreeSet<T>.

The constructed priority queue has the initial capacity of 110% of the size of the sorted set. The priority queue will have the same comparator as the sorted set.

Declaration

public PriorityQueue(TreeSet<T> collection)

Parameters

Type	Name	Description
TreeSet<T>	collection	the sorted set whose elements are to be placed into this priority queue

Exceptions

Type	Condition
System.InvalidCastException	if elements of `collection` cannot be compared to one another according to `collection`'s ordering
System.ArgumentNullException	if the specified collection or any of its elements are null

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PriorityQueue(ICollection<T>)

Creates a PriorityQueue<T> containing the elements in the specified collection. If the specified collection is an instance of a System.Collections.Generic.SortedSet<T>, TreeSet<T>, or is another PriorityQueue<T>, this priority queue will be ordered according to the same ordering. Otherwise, this priority queue will be ordered according to the System.IComparable<T> natural ordering of its elements.

Declaration

public PriorityQueue(ICollection<T> collection)

Parameters

Type	Name	Description
System.Collections.Generic.ICollection<T>	collection	collection to be inserted into priority queue

Exceptions

Type	Condition
System.InvalidCastException	if elements of the specified collection cannot be compared to one another according to the priority queue's ordering

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PriorityQueue(IComparer<T>)

Constructs a priority queue with the specified capacity and comparer.

Declaration

public PriorityQueue(IComparer<T> comparer)

Parameters

Type	Name	Description
System.Collections.Generic.IComparer<T>	comparer	The System.Collections.Generic.IComparer<T> that will be used to order this priority queue. If `null`, the System.IComparable<T> natural ordering of the elements will be used.

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PriorityQueue(SortedSet<T>)

Creates a PriorityQueue<T> containing the elements in the specified System.Collections.Generic.SortedSet<T>. This priority queue will be ordered according to the same ordering as the given System.Collections.Generic.SortedSet<T>.

The constructed priority queue has the initial capacity of 110% of the size of the sorted set. The priority queue will have the same comparator as the sorted set.

Declaration

public PriorityQueue(SortedSet<T> collection)

Parameters

Type	Name	Description
System.Collections.Generic.SortedSet<T>	collection	the sorted set whose elements are to be placed into this priority queue

Exceptions

Type	Condition
System.InvalidCastException	if elements of `collection` cannot be compared to one another according to `collection`'s ordering
System.ArgumentNullException	if the specified collection or any of its elements are null

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PriorityQueue(Int32)

Constructs a priority queue with the specified capacity and natural ordering.

Declaration

public PriorityQueue(int initialCapacity)

Parameters

Type	Name	Description
System.Int32	initialCapacity	initial capacity

Exceptions

Type	Condition
System.ArgumentOutOfRangeException	if the `initialCapacity` is less than 1.

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PriorityQueue(Int32, IComparer<T>)

Creates a PriorityQueue<T> with the specified initial capacity that orders its elements according to the specified comparer.

Declaration

public PriorityQueue(int initialCapacity, IComparer<T> comparer)

Parameters

Type	Name	Description
System.Int32	initialCapacity	the initial capacity for this priority queue
System.Collections.Generic.IComparer<T>	comparer	The System.Collections.Generic.IComparer<T> that will be used to order this priority queue. If `null`, the System.IComparable<T> natural ordering of the elements will be used.

Exceptions

Type	Condition
System.ArgumentOutOfRangeException	if the `initialCapacity` is less than 1

Properties

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Comparer

Gets the System.Collections.Generic.IComparer<T> used to order the elements in this queue, or Lucene.Net.Util.ArrayUtil.NaturalComparer`1 if this queue is sorted according to the System.IComparable<T> natural ordering of its elements.

Declaration

public virtual IComparer<T> Comparer { get; }

Property Value

Type	Description
System.Collections.Generic.IComparer<T>

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Count

Gets the size of the priority queue. If the size of the queue is greater than the System.Int32.MaxValue, then it returns System.Int32.MaxValue.

Declaration

public virtual int Count { get; }

Property Value

Type	Description
System.Int32

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IsReadOnly

Gets a value indicating whether the collection is read-only.

Declaration

public virtual bool IsReadOnly { get; }

Property Value

Type	Description
System.Boolean

Remarks

For priority queue this property returns false.

Methods

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Add(T)

Adds the specified object to the priority queue.

Declaration

public virtual void Add(T item)

Parameters

Type	Name	Description
T	item	the object to be added.

Exceptions

Type	Condition
System.InvalidCastException	if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering
System.ArgumentNullException	if `item` is `null`.

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AddAll(ICollection<T>)

Declaration

public virtual bool AddAll(ICollection<T> collection)

Parameters

Type	Name	Description
System.Collections.Generic.ICollection<T>	collection

Returns

Type	Description
System.Boolean

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Clear()

Removes all of the elements from this priority queue.

Declaration

public virtual void Clear()

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Contains(T)

Returns true if this queue contains the specified element. More formally, returns true if and only if this queue contains at least one element item such that o.Equals(item).

Declaration

public virtual bool Contains(T item)

Parameters

Type	Name	Description
T	item	The object to locate in the priority queue

Returns

Type	Description
System.Boolean	`true` if item is found in the priority queue; otherwise, `false.`

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CopyTo(T[], Int32)

Copies the elements of the priority queue to an Array, starting at a particular Array index.

Declaration

public virtual void CopyTo(T[] array, int arrayIndex)

Parameters

Type	Name	Description
T[]	array	The one-dimensional Array that is the destination of the elements copied from the priority queue. The Array must have zero-based indexing.
System.Int32	arrayIndex	The zero-based index in array at which copying begins.

Remarks

It is not guaranteed that items will be copied in the sorted order.

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Element()

Retrieves, but does not remove, the head of this queue. This method differs from Peek() only in that it throws an exception if this queue is empty.

This implementation returns the result of Peek() unless the queue is empty.

Declaration

public virtual T Element()

Returns

Type	Description
T	the head of this queue

Exceptions

Type	Condition
System.Collections.Generic.KeyNotFoundException	if this queue is empty

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GetEnumerator()

Gets the enumerator of the priority queue, which will not return elements in any specified ordering.

Declaration

public virtual IEnumerator<T> GetEnumerator()

Returns

Type	Description
System.Collections.Generic.IEnumerator<T>	The enumerator of the priority queue.

Remarks

Returned enumerator does not iterate elements in sorted order.

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Offer(T)

Inserts the specified element into this priority queue.

Declaration

public virtual bool Offer(T item)

Parameters

Type	Name	Description
T	item	the element to add to the priority queue.

Returns

Type	Description
System.Boolean	always `true`

Exceptions

Type	Condition
System.InvalidCastException	if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering
System.ArgumentNullException	if the specified element is null

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Peek()

Gets but does not remove the head of the queue.

Declaration

public virtual T Peek()

Returns

Type	Description
T	the head of the queue or null if the queue is empty.

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Poll()

Gets and removes the head of the queue.

Declaration

public virtual T Poll()

Returns

Type	Description
T	the head of the queue or null if the queue is empty.

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Remove()

Retrieves and removes the head of this queue. This method differs from Poll() only in that it throws an exception if this queue is empty.

This implementation returns the result of Poll() unless the queue is empty.

Declaration

public virtual T Remove()

Returns

Type	Description
T	the head of this queue

Exceptions

Type	Condition
System.Collections.Generic.KeyNotFoundException	if this queue is empty

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Remove(T)

Removes the specified object from the priority queue.

Declaration

public virtual bool Remove(T item)

Parameters

Type	Name	Description
T	item	the object to be removed.

Returns

Type	Description
System.Boolean	`true` if the object was in the priority queue, `false` if the object

Explicit Interface Implementations

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IEnumerable.GetEnumerator()

Returns an enumerator that iterates through the collection.

Declaration

IEnumerator IEnumerable.GetEnumerator()

Returns

Type	Description
System.Collections.IEnumerator	Enumerator

Remarks

Returned enumerator does not iterate elements in sorted order.

Implements

System.Collections.Generic.ICollection<T>

System.Collections.Generic.IEnumerable<T>

System.Collections.IEnumerable

Extension Methods

EnumerableExtensions.InPairs<T, TOut>(IEnumerable<T>, Func<T, T, TOut>)

Number.IsNumber(Object)

SetExtensions.RemoveAll<T>(ICollection<T>, IEnumerable<T>)

SetExtensions.AddAll<T>(ICollection<T>, IEnumerable<T>)