Class BinaryArrayWeakHeap<K>
- Type Parameters:
K
- the type of keys maintained by this heap
- All Implemented Interfaces:
Serializable
,Heap<K>
- Direct Known Subclasses:
BinaryArrayBulkInsertWeakHeap
Comparator
provided at heap creation time, depending on which
constructor is used.
The implementation uses an array in order to store the elements and
automatically maintains the size of the array much like a
Vector
does, providing amortized O(log(n)) time cost for
the insert
and deleteMin
operations. Operation
findMin
, is a worst-case O(1) operation. The bounds are worst-case if
the user initializes the heap with a capacity larger or equal to the total
number of elements that are going to be inserted into the heap.
Constructing such a heap from an array of elements can be performed using the
method heapify(Object[])
or heapify(Object[], Comparator)
in linear time.
Note that the ordering maintained by a binary heap, like any heap, and
whether or not an explicit comparator is provided, must be consistent
with equals
if this heap is to correctly implement the
Heap
interface. (See Comparable
or Comparator
for a
precise definition of consistent with equals.) This is so because
the Heap
interface is defined in terms of the equals
operation, but a binary heap performs all key comparisons using its
compareTo
(or compare
) method, so two keys that are deemed
equal by this method are, from the standpoint of the binary heap, equal. The
behavior of a heap is well-defined even if its ordering is
inconsistent with equals
; it just fails to obey the general contract
of the Heap
interface.
Note that this implementation is not synchronized. If multiple threads access a heap concurrently, and at least one of the threads modifies the heap structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements or changing the key of some element.) This is typically accomplished by synchronizing on some object that naturally encapsulates the heap.
- See Also:
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
Default initial capacity of the binary heap.protected BitSet
Reverse bitsprivate static final long
Fields inherited from class org.jheaps.array.AbstractArrayWeakHeap
array, comparator, DOWNSIZING_MIN_HEAP_CAPACITY, MAX_HEAP_CAPACITY, MIN_HEAP_CAPACITY, minCapacity, size
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Constructor Summary
ConstructorsConstructorDescriptionConstructs a new, empty heap, using the natural ordering of its keys.BinaryArrayWeakHeap
(int capacity) Constructs a new, empty heap, with a provided initial capacity using the natural ordering of its keys.BinaryArrayWeakHeap
(Comparator<? super K> comparator) Constructs a new, empty heap, ordered according to the given comparator.BinaryArrayWeakHeap
(Comparator<? super K> comparator, int capacity) Constructs a new, empty heap, with a provided initial capacity ordered according to the given comparator. -
Method Summary
Modifier and TypeMethodDescriptionprotected int
dancestor
(int j) Return the distinguished ancestor of an element.Delete and return an element with the minimum key.protected void
ensureCapacity
(int capacity) Ensure that the array representation has the necessary capacity.findMin()
Find an element with the minimum key.protected void
fixdown
(int j) Downwards fix starting from a particular elementprotected void
fixdownWithComparator
(int j) Downwards fix starting from a particular element.protected void
fixup
(int j) Upwards fix starting from a particular elementprotected void
fixupWithComparator
(int j) Upwards fix starting from a particular element.static <K> BinaryArrayWeakHeap<K>
heapify
(K[] array) Create a heap from an array of elements.static <K> BinaryArrayWeakHeap<K>
heapify
(K[] array, Comparator<? super K> comparator) Create a heap from an array of elements.protected void
initCapacity
(int capacity) Initialize array representation.void
Insert a key into the heap.protected boolean
join
(int i, int j) Join two weak heaps into one.protected boolean
joinWithComparator
(int i, int j) Join two weak heaps into one.Methods inherited from class org.jheaps.array.AbstractArrayWeakHeap
checkCapacity, clear, comparator, isEmpty, size
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Field Details
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serialVersionUID
private static final long serialVersionUID- See Also:
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DEFAULT_HEAP_CAPACITY
public static final int DEFAULT_HEAP_CAPACITYDefault initial capacity of the binary heap.- See Also:
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reverse
Reverse bits
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Constructor Details
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BinaryArrayWeakHeap
public BinaryArrayWeakHeap()Constructs a new, empty heap, using the natural ordering of its keys.All keys inserted into the heap must implement the
Comparable
interface. Furthermore, all such keys must be mutually comparable:k1.compareTo(k2)
must not throw aClassCastException
for any keysk1
andk2
in the heap. If the user attempts to put a key into the heap that violates this constraint (for example, the user attempts to put a string key into a heap whose keys are integers), theinsert(Object key)
call will throw aClassCastException
.The initial capacity of the heap is
DEFAULT_HEAP_CAPACITY
and adjusts automatically based on the sequence of insertions and deletions. -
BinaryArrayWeakHeap
public BinaryArrayWeakHeap(int capacity) Constructs a new, empty heap, with a provided initial capacity using the natural ordering of its keys.All keys inserted into the heap must implement the
Comparable
interface. Furthermore, all such keys must be mutually comparable:k1.compareTo(k2)
must not throw aClassCastException
for any keysk1
andk2
in the heap. If the user attempts to put a key into the heap that violates this constraint (for example, the user attempts to put a string key into a heap whose keys are integers), theinsert(Object key)
call will throw aClassCastException
.The initial capacity of the heap is provided by the user and is adjusted automatically based on the sequence of insertions and deletions. The capacity will never become smaller than the initial requested capacity.
- Parameters:
capacity
- the initial heap capacity
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BinaryArrayWeakHeap
Constructs a new, empty heap, ordered according to the given comparator.All keys inserted into the heap must be mutually comparable by the given comparator:
comparator.compare(k1, k2)
must not throw aClassCastException
for any keysk1
andk2
in the heap. If the user attempts to put a key into the heap that violates this constraint, theinsert(Object key)
call will throw aClassCastException
.The initial capacity of the heap is
DEFAULT_HEAP_CAPACITY
and adjusts automatically based on the sequence of insertions and deletions.- Parameters:
comparator
- the comparator that will be used to order this heap. Ifnull
, the natural ordering of the keys will be used.
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BinaryArrayWeakHeap
Constructs a new, empty heap, with a provided initial capacity ordered according to the given comparator.All keys inserted into the heap must be mutually comparable by the given comparator:
comparator.compare(k1, k2)
must not throw aClassCastException
for any keysk1
andk2
in the heap. If the user attempts to put a key into the heap that violates this constraint, theinsert(Object key)
call will throw aClassCastException
.The initial capacity of the heap is provided by the user and is adjusted automatically based on the sequence of insertions and deletions. The capacity will never become smaller than the initial requested capacity.
- Parameters:
comparator
- the comparator that will be used to order this heap. Ifnull
, the natural ordering of the keys will be used.capacity
- the initial heap capacity
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Method Details
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heapify
Create a heap from an array of elements. The elements of the array are not destroyed. The method has linear time complexity.- Type Parameters:
K
- the type of keys maintained by the heap- Parameters:
array
- an array of elements- Returns:
- a heap
- Throws:
IllegalArgumentException
- in case the array is null
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heapify
Create a heap from an array of elements. The elements of the array are not destroyed. The method has linear time complexity.- Type Parameters:
K
- the type of keys maintained by the heap- Parameters:
array
- an array of elementscomparator
- the comparator to use- Returns:
- a heap
- Throws:
IllegalArgumentException
- in case the array is null
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findMin
Find an element with the minimum key. -
insert
Insert a key into the heap. -
deleteMin
Delete and return an element with the minimum key. If multiple such elements exists, only one of them will be deleted. -
initCapacity
protected void initCapacity(int capacity) Description copied from class:AbstractArrayWeakHeap
Initialize array representation.- Specified by:
initCapacity
in classAbstractArrayWeakHeap<K>
- Parameters:
capacity
- the capacity
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ensureCapacity
protected void ensureCapacity(int capacity) Ensure that the array representation has the necessary capacity.- Specified by:
ensureCapacity
in classAbstractArrayWeakHeap<K>
- Parameters:
capacity
- the requested capacity
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dancestor
protected int dancestor(int j) Return the distinguished ancestor of an element.- Parameters:
j
- the element- Returns:
- the distinguished ancestor of the element
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join
protected boolean join(int i, int j) Join two weak heaps into one.- Parameters:
i
- root of the first weak heapj
- root of the second weak heap- Returns:
- true if already a weak heap, false if a flip was needed
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joinWithComparator
protected boolean joinWithComparator(int i, int j) Join two weak heaps into one.- Parameters:
i
- root of the first weak heapj
- root of the second weak heap- Returns:
- true if already a weak heap, false if a flip was needed
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fixup
protected void fixup(int j) Description copied from class:AbstractArrayWeakHeap
Upwards fix starting from a particular element- Specified by:
fixup
in classAbstractArrayWeakHeap<K>
- Parameters:
j
- the index of the starting element
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fixupWithComparator
protected void fixupWithComparator(int j) Description copied from class:AbstractArrayWeakHeap
Upwards fix starting from a particular element. Performs comparisons using the comparator.- Specified by:
fixupWithComparator
in classAbstractArrayWeakHeap<K>
- Parameters:
j
- the index of the starting element
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fixdown
protected void fixdown(int j) Description copied from class:AbstractArrayWeakHeap
Downwards fix starting from a particular element- Specified by:
fixdown
in classAbstractArrayWeakHeap<K>
- Parameters:
j
- the index of the starting element
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fixdownWithComparator
protected void fixdownWithComparator(int j) Description copied from class:AbstractArrayWeakHeap
Downwards fix starting from a particular element. Performs comparisons using the comparator.- Specified by:
fixdownWithComparator
in classAbstractArrayWeakHeap<K>
- Parameters:
j
- the index of the starting element
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