 All Implemented Interfaces:
IntPriorityQueue
,Copyable<IntBinaryHeap>
Priority order: IntBinaryHeap instances are created via factory methods with names
beginning with create
. The priority order depends upon the factory method used to
create the IntBinaryHeap. Methods named createMinHeap
produce a min heap with
priority order minimumpriorityfirstout. Methods named createMaxHeap
produce a max
heap with priority order maximumpriorityfirstout.
Creating instances: To create an instance, use one of the factory methods. In this example an IntBinaryHeap with an element domain of [0,100) is created:
IntBinaryHeap<String> pq = IntBinaryHeap.createMinHeap(100);
In the above example, the element domain is [0,100) and the IntBinaryHeap is initially empty.
Purpose: The purpose of such an IntBinaryHeap is to support implementations of
algorithms that require such a specialized case. For example, some graph algorithms such as
Dijkstra's algorithm for singlesource shortest paths, and Prim's algorithm for minimum spanning
tree, rely on a priority queue of the vertex ids, which are usually ints in some finite range.
Although such applications could use the classes that instead implement the PriorityQueue
interface, using Java's wrapper type Integer
, the classes that implement IntPriorityQueue
that specialize the element type to int are optimized for this special case.
For a more general purpose binary heap, see the BinaryHeap
class.
Method runtimes: The asymptotic runtime of the methods of this class are as follows (where n is the current size of the heap):
 O(1):
contains(int)
,createMaxHeap(int)
,createMinHeap(int)
,domain()
,isEmpty()
,peek()
,peekPriority()
,peekPriority(int)
,size()
 O(lg n):
change(int,int)
,demote(int,int)
,offer(int, int)
,poll()
,promote(int,int)
 O(n):
clear()
,copy()

Method Summary
Modifier and TypeMethodDescriptionboolean
change
(int element, int priority) Changes the priority of an element if the element is present in the IntPriorityQueue, and otherwise adds the (element, priority) pair to the IntPriorityQueue.final void
clear()
Clears the IntPriorityQueue, removing all elements.final boolean
contains
(int element) Checks if an element is in the IntPriorityQueue.copy()
Creates an identical copy of this object.static IntBinaryHeap
createMaxHeap
(int n) Initializes an empty maxheap of (int, priority) pairs, such that the domain of the elements are the integers in [0, n).static IntBinaryHeap
createMinHeap
(int n) Initializes an empty minheap of (int, priority) pairs, such that the domain of the elements are the integers in [0, n).boolean
demote
(int element, int priority) Demotes an element relative to priority order if the element is present in the IntPriorityQueue.final int
domain()
Returns the domain of this IntPriorityQueue.final boolean
isEmpty()
Checks if the IntPriorityQueue is empty.boolean
offer
(int element, int priority) Adds an (element, priority) pair to the IntPriorityQueue with a specified priority, provided the element is not already in the IntPriorityQueue.final int
peek()
Gets the next element in priority order from this IntPriorityQueue, without removing it.int
Gets the priority of the next element in priority order in the IntPriorityQueue.int
peekPriority
(int element) Gets the current priority of a specified element in the IntPriorityQueue.final int
poll()
Gets and removes the next element in priority order from this IntPriorityQueue.boolean
promote
(int element, int priority) Promotes an element relative to priority order if the element is present in the IntPriorityQueue.final int
size()
Gets the current size of the IntPriorityQueue, which is the number of (element, priority) pairs that it contains.

Method Details

copy
Description copied from interface:Copyable
Creates an identical copy of this object. Specified by:
copy
in interfaceCopyable<IntBinaryHeap>
 Returns:
 an identical copy of this object.

change
public boolean change(int element, int priority) Changes the priority of an element if the element is present in the IntPriorityQueue, and otherwise adds the (element, priority) pair to the IntPriorityQueue. Specified by:
change
in interfaceIntPriorityQueue
 Parameters:
element
 The element whose priority is to change.priority
 Its new priority. Returns:
 true if and only if the IntPriorityQueue changed as a consequence of this method call.
 Throws:
IndexOutOfBoundsException
 if element is negative, or if element is greater than or equal to the domain n.

clear
public final void clear()Description copied from interface:IntPriorityQueue
Clears the IntPriorityQueue, removing all elements. Specified by:
clear
in interfaceIntPriorityQueue

contains
public final boolean contains(int element) Checks if an element is in the IntPriorityQueue. Specified by:
contains
in interfaceIntPriorityQueue
 Parameters:
element
 The element to check for containment. Returns:
 true if and only if there exists an (element, priority) pair for the specified element.
 Throws:
IndexOutOfBoundsException
 if element is negative, or if element is greater than or equal to the domain n.

createMaxHeap
Initializes an empty maxheap of (int, priority) pairs, such that the domain of the elements are the integers in [0, n). Parameters:
n
 The size of the domain of the elements of the maxheap. Returns:
 an empty maxheap
 Throws:
IllegalArgumentException
 if n is nonpositive

createMinHeap
Initializes an empty minheap of (int, priority) pairs, such that the domain of the elements are the integers in [0, n). Parameters:
n
 The size of the domain of the elements of the minheap. Returns:
 an empty minheap
 Throws:
IllegalArgumentException
 if n is nonpositive

demote
public boolean demote(int element, int priority) Demotes an element relative to priority order if the element is present in the IntPriorityQueue. For a minheap, demotion means increasing the element's priority, while for a maxheap, demotion means decreasing its priority. If the element is not in the IntPriorityQueue, or if its new priority is not a demotion, then this method does nothing. Specified by:
demote
in interfaceIntPriorityQueue
 Parameters:
element
 The element whose priority is to change.priority
 Its new priority. Returns:
 true if and only if the IntPriorityQueue changed as a consequence of this method call.
 Throws:
IndexOutOfBoundsException
 if element is negative, or if element is greater than or equal to the domain n.

domain
public final int domain()Description copied from interface:IntPriorityQueue
Returns the domain of this IntPriorityQueue. Note that the domain is not the same thing as the size. The domain defines the elements that are allowed in the IntPriorityQueue, whether or not they actually appear within it. Specified by:
domain
in interfaceIntPriorityQueue
 Returns:
 the domain of this IntPriorityQueue

isEmpty
public final boolean isEmpty()Description copied from interface:IntPriorityQueue
Checks if the IntPriorityQueue is empty. Specified by:
isEmpty
in interfaceIntPriorityQueue
 Returns:
 true if and only if it is empty

offer
public boolean offer(int element, int priority) Adds an (element, priority) pair to the IntPriorityQueue with a specified priority, provided the element is not already in the IntPriorityQueue. Specified by:
offer
in interfaceIntPriorityQueue
 Parameters:
element
 The element.priority
 The priority of the element. Returns:
 true if the (element, priority) pair was added, and false if the IntPriorityQueue already contained the element.
 Throws:
IndexOutOfBoundsException
 if element is negative, or if element is greater than or equal to the domain n.

peek
public final int peek()Description copied from interface:IntPriorityQueue
Gets the next element in priority order from this IntPriorityQueue, without removing it. Behavior is undefined if it is empty. Specified by:
peek
in interfaceIntPriorityQueue
 Returns:
 the next element in priority order.

peekPriority
public int peekPriority()Description copied from interface:IntPriorityQueue
Gets the priority of the next element in priority order in the IntPriorityQueue. Behavior is undefined if it is empty. Specified by:
peekPriority
in interfaceIntPriorityQueue
 Returns:
 the priority of the next element in priority order.

peekPriority
public int peekPriority(int element) Gets the current priority of a specified element in the IntPriorityQueue. Behavior is undefined if the IntPriorityQueue doesn't contain the element. Specified by:
peekPriority
in interfaceIntPriorityQueue
 Parameters:
element
 the element whose priority is returned Returns:
 the current priority of element.
 Throws:
IndexOutOfBoundsException
 if element is negative, or if element is greater than or equal to the domain n.

poll
public final int poll()Description copied from interface:IntPriorityQueue
Gets and removes the next element in priority order from this IntPriorityQueue. Behavior is undefined if it is empty. Specified by:
poll
in interfaceIntPriorityQueue
 Returns:
 the next element in priority order.

promote
public boolean promote(int element, int priority) Promotes an element relative to priority order if the element is present in the IntPriorityQueue. For a minheap, promotion means decreasing the element's priority, while for a maxheap, promotion means increasing its priority. If the element is not in the IntPriorityQueue, or if its new priority is not a promotion, then this method does nothing. Specified by:
promote
in interfaceIntPriorityQueue
 Parameters:
element
 The element whose priority is to change.priority
 Its new priority. Returns:
 true if and only if the IntPriorityQueue changed as a consequence of this method call.
 Throws:
IndexOutOfBoundsException
 if element is negative, or if element is greater than or equal to the domain n.

size
public final int size()Description copied from interface:IntPriorityQueue
Gets the current size of the IntPriorityQueue, which is the number of (element, priority) pairs that it contains. Specified by:
size
in interfaceIntPriorityQueue
 Returns:
 the current size of the IntPriorityQueue.
