Matakuliah
Tahun
Versi
: T0026/Struktur Data
: 2005
: 1/1
Pertemuan 20
Fibonacci Heap
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat merumuskan program
modular untuk mengimplementasikan
Binomial dan fibonacci heap
2
Fibonacci Heaps
Insert
Actual
O(1)
Amortized
O(1)
Remove min (or max) O(n)
O(log n)
Meld
O(1)
O(1)
Remove
O(n)
O(log n)
Decrease key (or
increase)
O(n)
O(1)
3
Single Source All Destinations
Shortest Paths
1
6
8
2
16
3
7
6
3
1
5
4
10
4
2
5
4
3
7
14
4
Greedy Single Source All Destinations
• Known as Dijkstra’s algorithm.
• Let d(i) be the length of a shortest one edge
extension of an already generated shortest
path, the one edge extension ends at vertex
i.
• The next shortest path is to an as yet
unreached vertex for which the d() value is
least.
• After the next shortest path is generated,
some d() values are updated (decreased).
Operations On d()
• Remove min.
– Done O(n) times, where n is the number of
vertices in the graph.
• Decrease d().
– Done O(e) times, where e is the number of
edges in the graph.
• Array.
– O(n2) overall complexity.
• Min heap.
– O(nlog n + elog n) overall complexity.
• Fibonacci heap.
– O(nlog n + e) overall complexity.
6
Prim’s Min-Cost Spanning Tree
Algorithm
• Array.
– O(n2) overall complexity.
• Min heap.
– O(nlog n + elog n) overall complexity.
• Fibonacci heap.
– O(nlog n + e) overall complexity.
7
Min Fibonacci Heap
• Collection of min trees.
• The min trees need not be Binomial
trees.
8
Node Structure
• Degree, Child, Data
• Left and Right Sibling
– Used for circular doubly linked list of siblings.
• Parent
– Pointer to parent node.
• ChildCut
– True if node has lost a child since it became a
child of its current parent.
– Set to false by remove min, which is the only
operation that makes one node a child of
another.
– Undefined for a root node.
9
Fibonacci Heap Representation
A
2
1
4
4
6
5
7
9
7
6
3
8
5
5
8
6
9
9
• Parent and ChildCut fields not shown.
10
Remove(theNode)
• theNode points to the Fibonacci heap
node that contains the element that is to
be removed.
• theNode points to min element => do a
remove min.
– In this case, complexity is the same as that
for remove min.
11
Remove(theNode)
6
1
5
theNode
2
4
6
5
7
6
7
4
9
10
5
3
9
8
9
8
Remove theNode from its doubly linked sibling list.
13
Remove(theNode)
1
7
2
4
6
5
7
9
6
5
3
8
6
8
Combine top-level list and children of theNode.
9
4
10
5
9
14
Remove(theNode)
10
1
5
6
9
2
4
5
7
7
9
6
5
3
9
8
6
8
15
DecreaseKey(theNode, theAmount)
6
1
5
theNode
2
4
6
8
5
7
6
7
4
9
10
5
3
9
8
9
If theNode is not a root and new key < parent
key, remove subtree rooted at theNode from its
doubly linked sibling list.
Insert into top-level list.
16
DecreaseKey(theNode, theAmount)
0
10
1
5
2
9
4
6
7
5
7
9
6
5
3
9
8
6
8
17
Cascading Cut
• When theNode is cut out of its sibling list in
a remove or decrease key operation, follow
path from parent of theNode to the root.
• Encountered nodes (other than root) with
ChildCut = true are cut from their sibling lists
and inserted into top-level list.
• Stop at first node with ChildCut = false.
• For this node, set ChildCut = true.
18
Cascading Cut Example
1
2 F
3
7
8
T
5
T 7
6
4
6
9
8
theNode
9
8
9
Decrease key by 2.
19
Cascading Cut Example
1
6
2 F
3
7
8
T
5
T 7
6
4
6
9
9
8
9
20
Cascading Cut Example
1
6
2 F
3
7
8
4
6
T
5
9
9
7
8
9
6
21
Cascading Cut Example
1
7
8
3
6
2 F
5
9
9
4
7
8
6
9
6
22
Cascading Cut Example
1
7
8
3
6
2 T
5
9
9
4
7
8
6
9
6
Actual complexity of cascading cut is O(h) = O(n).
23