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CSC 213 – Large Scale Programming. Lecture 39: The Rolling Stones, Masters of the Balanced Tree. (2,4) Trees: Pro & Con. Cons: Cannot reuse BST code , since it is not binary tree Pros: (2,4) Trees balance without rotations Fewer balancing cases than AVL or splay trees. - PowerPoint PPT Presentation
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LECTURE 39:THE ROLLING STONES, MASTERS OF THE BALANCED TREE
CSC 213 – Large Scale Programming
(2,4) Trees: Pro & Con
Cons: Cannot reuse BST code, since it is not
binary treePros: (2,4) Trees balance without rotations Fewer balancing cases than AVL or splay
trees
(2,4) Trees: Pro & Con
Cons: Cannot reuse BST code, since it is not
binary treePros: (2,4) Trees balance without rotations Fewer balancing cases than AVL or splay
trees
Sick, twisted, & wrong: n-node naming scheme is crime against
humanity
Red-Black Trees
Represents a (2,4) tree using binary tree Red node when Entry & parent’s Entry share
node (2,4) tree Black node’s Entry also in child of parent’s node
in (2,4) tree 2 6 73 54
4 62 7
53
35OR
Red-Black Trees
Represents a (2,4) tree using binary tree Red node when Entry & parent’s Entry share
node (2,4) tree Black node’s Entry also in child of parent’s node
in (2,4) tree
Maximizes code reuse, since subclass of BST
2 6 73 54
4 62 7
53
35OR
Red-Black Tree Properties
Root Property: Root node painted black External Property: Leaves are painted
black Internal Property: Red nodes’ children are
black Depth Property: Leaves have identical
black depth Number of black ancestors for the node
9
154
62 12
7
21
Insertion
Begins as BST insertion (just like splay & AVL)
New node’s initial color set by where it is If node is root, paint it black Other nodes colored red when insertion
completes
Insertion
Begins as BST insertion (just like splay & AVL)
New node’s initial color set by where it is If node is root, paint it black Other nodes colored red when insertion
completes Example: insert(3)
68
Insertion
Begins as BST insertion (just like splay & AVL)
New node’s initial color set by where it is If node is root, paint it black Other nodes colored red when insertion
completes Example: insert(3)
683
Insertion
Begins as BST insertion (just like splay & AVL)
New node’s initial color set by where it is If node is root, paint it black Other nodes colored red when insertion
completes Example: insert(3)
683
Insertion
New node’s initial color set by where it is If node is root, paint it black Other nodes colored red when insertion
completes If node’s parent is red, violates internal
property Must reorganize tree to remove double
red Example: insert(4)
683
4
Insertion
New node’s initial color set by where it is If node is root, paint it black Other nodes colored red when insertion
completes If node’s parent is red, violates internal
property Must reorganize tree to remove double
red Example: insert(4)makes tree
unbalanced
683
4
Double Red With Red Aunt
Double red represents creation of 5-node
Perform recoloring (equivalent to (2,4) tree split)
3 4 6 86
83
4
Double Red With Red Aunt
Parent & uncle painted black, grandparent red When grandparent is root, must paint it
black When easier, promote 2nd Entry to parent
As in splitting, double red may propagate up
2 4 6 7
Double Red With Red Aunt
Parent & uncle painted black, grandparent red When grandparent is root, must paint it
black When easier, promote 2nd Entry to parent
As in splitting, double red may propagate up
2 4 6 76 7
… 4 …
2
Double Red With Red Aunt
Parent & uncle painted black, grandparent red When grandparent is root, must paint it
black When easier, promote 2nd Entry to parent
As in splitting, double red may propagate up
2 4 6 76 7
… 4 …
2
4
672
Double Red With Red Aunt
Parent & uncle painted black, grandparent red When grandparent is root, must paint it
black When easier, promote 2nd Entry to parent
As in splitting, double red may propagate up
2 4 6 76 7
… 4 …
2
4
672
4
672
Double Red With Red Aunt
Parent & uncle painted black, grandparent red When grandparent is root, must paint it
black When easier, promote 2nd Entry to parent
As in splitting, double red may propagate up
2 4 6 76 7
… 4 …
2
4
672
4
672
Double Red With Black Aunt
Poorly balanced 4-node causes this double red Restore tree balance to use AVL tree
restructuring Preserves overall balance of the tree
3 4 6683
48
Double Red With Black Aunt
Rebalance tree using AVL tree restructuring
Recolor nodes, but no changes (2,4) tree 4
672
Double Red With Black Aunt
Rebalance tree using AVL tree restructuring
Recolor nodes, but no changes (2,4) tree 4
672 4
67
2
Double Red With Black Aunt
Rebalance tree using AVL tree restructuring
Recolor nodes, but no changes (2,4) tree 4
672
4 6 7
.. 2 ..
46
72
Double Red With Black Aunt
Rebalance tree using AVL tree restructuring
Recolor nodes, but no changes (2,4) tree 4
672
4 6 7
.. 2 ..
46
72
4 6 7
.. 2 ..
Double Red Restructuring
4 different restructures needed to remedy Differ in how node, parent, & grandparent
related Identical result no matter where we start4
67
7
46
7
64
4
76
Double Red Restructuring
4 different restructures needed to remedy Differ in how node, parent, & grandparent
related Identical result no matter where we start4
67
7
46
7
64
4
76
4 76
Deletion
Start with normal BST deletion If Entry in red node or leafs’s sibling
red Leaf’s sibling is painted black
Example: remove(1)6
3 8
41
Deletion
Start with normal BST deletion If Entry in red node or leafs’s sibling
red Leaf’s sibling is painted black
Example: remove(1)6
3 8
41
Deletion
Start with normal BST deletion If Entry in red node or leafs’s sibling
red Leaf’s sibling is painted black
Example: remove(1)6
3 8
4
Deletion
Start with normal BST deletion If Entry in red node or leafs’s sibling
red Leaf’s sibling is painted black
Example: remove(1)6
3 8
4
What’s Blacker Than Black?
If removed Entry & leaf’s sibling already black Paint sibling double black This is an illegal state – violates internal
property Example: remove(8)6
3 8
4
What’s Blacker Than Black?
If removed Entry & leaf’s sibling already black Paint sibling double black This is an illegal state – violates internal
property Example: remove(8)6
3 8
4
What’s Blacker Than Black?
If removed Entry & leaf’s sibling already black Paint sibling double black This is an illegal state – violates internal
property Example: remove(8)6
3
4
What’s Blacker Than Black?
If removed Entry & leaf’s sibling already black Paint sibling double black This is an illegal state – violates internal
property Example: remove(8) causes double
black6
3
4
Remedying Double Black
Case 1: sibling is black with red child Reorder nodes using AVL tree restructure
Case 2: sibling and its children are black Equal to (2,4) tree underflow, so recolor
nodes
Remedying Double Black
Case 1: sibling is black with red child Reorder nodes using AVL tree restructure
Case 2: sibling and its children are black Equal to (2,4) tree underflow, so recolor
nodes Case 3: sibling is red
Adjust subtree to better represent 3-node Once complete apply case 1 or case 2
Black Sibling With Red Niece Solve double black using (2,4) tree
transfer…9…
6 8 10
9
6 10
8
Black Sibling With Red Niece Solve double black using (2,4) tree
transfer…9…
6 8
9
6
8
Black Sibling With Red Niece Solve double black using (2,4) tree
transfer …8…
6 9
…9…
6 8
9
6
8
Black Sibling With Red Niece Solve double black using (2,4) tree
transfer …8…
6 9
…9…
6 8
9
6
8
8
6 9
Black Sibling With Red Niece Solve double black using AVL
restructuring …8…
6 9
…9…
6 8
9
6
8
8
6 9
Sibling & Children are Black Solve double black using (2,4) tree
fusion5 9
6 10
5
10
9
6
…
…
Sibling & Children are Black Solve double black using (2,4) tree
fusion5 9
6
5
9
6
…
…
Sibling & Children are Black Solve double black using (2,4) tree
fusion5 9
6
5
9
6
…
…
5
… 6 9
Sibling & Children are Black Solve double black recoloring
parent & sibling5 9
6
5
9
6
…
…
5
… 6 9
5
9
6
…
Sibling & Children are Black Solve double black recoloring
parent & sibling5 9
6
5
9
6
…
…
5
… 6 9
5
9
6
…
Sibling & Children are Black If parent already black, it becomes
double black 4
1 10 1 4
41 10
41
4
Sibling is Red
Adjusting double black stalls for time Transforms situation into something we can
fix
9
5 10
4
Sibling is Red
Adjusting double black stalls for time Transforms situation into something we can
fix
9
5 10
4
Sibling is Red
Adjusting double black stalls for time Transforms situation into something we can
fix
9
5
4
Sibling is Red
Adjusting double black stalls for time Transforms situation into something we can
fix
9
5
4
Sibling is Red
Adjusting double black stalls for time Transforms situation into something we can
fix Once completed, re-examine double black
node9
5
4
54 9
Do the Activity
For Next Lecture
Weekly assignment available to test skills Due at regular time next Tuesday Talk to me if struggling on problems
Look at what all this means in real world code What are B-trees? How are they related to (2,4) & red-black
trees? Where are they used?
Reminder: project #3 tests due today