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Class: Heap
Object
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+--Collection
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+--SequenceableCollection
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+--Heap
- Package:
- stx:libbasic2
- Category:
- Collections-Sequenceable
- Version:
- rev:
1.9
date: 2019/02/10 13:51:26
- user: cg
- file: Heap.st directory: libbasic2
- module: stx stc-classLibrary: libbasic2
Class Heap implements a special data structure commonly referred to as 'heap'.
Heaps are more efficient than SortedCollections if:
a) Elements are only removed at the beginning
b) Elements are added with arbitrary sort order.
The sort time for a heap is O(n log n) in all cases.
Instance variables:
array <Array> the data repository
tally <Integer> the number of elements in the heap
sortBlock <Block|nil> a two-argument block defining the sort order,
or nil in which case the default sort order is
[:element1 :element2| element1 <= element2]
examples
-
documentation
-
Class Heap implements a special data structure commonly referred to as 'heap'.
Heaps are more efficient than SortedCollections if:
a) Elements are only removed at the beginning
b) Elements are added with arbitrary sort order.
The sort time for a heap is O(n log n) in all cases.
Instance variables:
array <Array> the data repository
tally <Integer> the number of elements in the heap
sortBlock <Block|nil> a two-argument block defining the sort order,
or nil in which case the default sort order is
[:element1 :element2| element1 <= element2]
-
examples
-
Create a sorted collection of numbers, remove the elements
sequentially and add new objects randomly.
Note: This is the kind of benchmark a heap is designed for.
[exBegin]
| n rnd array time sorted |
n := 50000.
rnd := Random new.
array := (1 to: n) collect:[:i| rnd next].
time := Time millisecondsToRun:[
sorted := Heap withAll: array.
1 to: n do:[:i|
sorted removeFirst.
sorted add: rnd next].
].
Transcript showCR:'Time for Heap: ', time printString,' msecs'.
time := Time millisecondsToRun:[
sorted := SortedCollection withAll: array.
1 to: n do:[:i|
sorted removeFirst.
sorted add: rnd next].
].
Transcript showCR:'Time for SortedCollection: ', time printString,' msecs'.
[exEnd]
Sort a random collection of Floats and compare the results with
SortedCollection (using the quick-sort algorithm) and
[exBegin]
| n rnd array out time sorted |
n := 40000.
rnd := Random new.
array := (1 to: n) collect:[:i| rnd next].
out := Array new: n.
time := Time millisecondsToRun:[
sorted := Heap withAll: array.
1 to: n do:[:i| sorted removeFirst].
].
Transcript showCR:'Time for heap-sort: ', time printString,' msecs'.
time := Time millisecondsToRun:[
sorted := SortedCollection withAll: array.
].
Transcript showCR:'Time for quick-sort: ', time printString,' msecs'.
[exEnd]
instance creation
-
new
-
-
new: n
-
-
sortBlock: aBlock
-
Create a new heap sorted by the given block
-
withAll: aCollection
-
Create a new heap with all the elements from aCollection
-
withAll: aCollection sortBlock: sortBlock
-
Create a new heap with all the elements from aCollection
accessing
-
at: index
-
Return the element at the given position within the receiver
-
at: index put: newObject
-
Heaps are accessed with #add: not #at:put:
-
first
-
Return the first element in the receiver
usage example(s):
-
firstOrNil
-
-
reSort
-
Resort the entire heap
-
size
-
Answer how many elements the receiver contains.
-
sortBlock
-
-
sortBlock: aBlock
-
adding
-
add: anObject
-
Include newObject as one of the receiver's elements. Answer newObject.
comparing
-
= anObject
-
enumerating
-
do: aBlock
-
Evaluate aBlock with each of the receiver's elements as the argument.
growing
-
grow
-
Become larger.
-
growSize
-
Return the size by which the receiver should grow if there are no empty slots left.
-
growTo: newSize
-
Grow to the requested size.
-
trim
-
Remove any empty slots in the receiver.
private
-
array
-
-
privateRemoveAt: index
-
Remove the element at the given index and make sure the sorting order is okay.
Return the removed object
-
setCollection: aCollection
-
-
setCollection: aCollection tally: newTally
-
-
species
-
private-heap
-
downHeap: anIndex
-
Check the heap downwards for correctness starting at anIndex.
Everything above (i.e. left of) anIndex is ok.
-
downHeapSingle: anIndex
-
This version is optimized for the case when only one element in the receiver can be at a wrong position. It avoids one comparison at each node when travelling down the heap and checks the heap upwards after the element is at a bottom position. Since the probability for being at the bottom of the heap is much larger than for being somewhere in the middle this version should be faster.
-
upHeap: anIndex
-
Check the heap upwards for correctness starting at anIndex.
Everything below anIndex is ok.
queries
-
isEmpty
-
Answer whether the receiver contains any elements.
-
sorts: element1 before: element2
-
Return true if element1 should be sorted before element2.
This method defines the sort order in the receiver
removing
-
remove: oldObject ifAbsent: aBlock
-
Remove the first occurrence of oldObject as one of the receiver's elements.
If several of the elements are equal to oldObject, only one is removed.
If no element is equal to oldObject, answer the result of evaluating anExceptionBlock.
Otherwise, answer the removed object
(which may be non-identical, but equal to oldObject)
-
removeAt: index
-
Remove the element at given position
-
removeFirst
-
Remove the first element from the receiver
-
removeIdentical: oldObject ifAbsent: aBlock
-
Remove the first occurrence of oldObject as one of the receiver's elements.
If oldObject is present multiple times, only the first occurrence is removed.
If oldObject is not present, answer the result of evaluating anExceptionBlock.
Otherwise, answer the argument, oldObject.
testing
-
isFixedSize
-
return true if the receiver cannot grow
-
isHeap
-
Create a sorted collection of numbers, remove the elements
sequentially and add new objects randomly.
Note: This is the kind of benchmark a heap is designed for.
| n rnd array time sorted |
n := 50000.
rnd := Random new.
array := (1 to: n) collect:[:i| rnd next].
time := Time millisecondsToRun:[
sorted := Heap withAll: array.
1 to: n do:[:i|
sorted removeFirst.
sorted add: rnd next].
].
Transcript showCR:'Time for Heap: ', time printString,' msecs'.
time := Time millisecondsToRun:[
sorted := SortedCollection withAll: array.
1 to: n do:[:i|
sorted removeFirst.
sorted add: rnd next].
].
Transcript showCR:'Time for SortedCollection: ', time printString,' msecs'.
|
Sort a random collection of Floats and compare the results with
SortedCollection (using the quick-sort algorithm) and
| n rnd array out time sorted |
n := 40000.
rnd := Random new.
array := (1 to: n) collect:[:i| rnd next].
out := Array new: n.
time := Time millisecondsToRun:[
sorted := Heap withAll: array.
1 to: n do:[:i| sorted removeFirst].
].
Transcript showCR:'Time for heap-sort: ', time printString,' msecs'.
time := Time millisecondsToRun:[
sorted := SortedCollection withAll: array.
].
Transcript showCR:'Time for quick-sort: ', time printString,' msecs'.
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