I
NTRODUCTION
TO
T
REES
Contents
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Introduction: Trees and Binary Trees
{
Representing Trees
±
Test
Yourself #1
{
Tree Traversals
±
Test Yourself #2
±
Test Yourself #3
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Answers to Self

Study Questions
Introduction
Lists, stacks, and queues, are all
linear
structures: in all three data structures, one item follows another.
Trees will be our first nonlinear structure:
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More than one item can follow another.
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The number of items that follow can vary from one item to another.
Trees have many uses:
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representing family genealogies
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as the underlying structure in decisionmaking algorithms
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to represent priority queues (a special kind of tree called a
heap
)
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to provide fast access to information in a database (a special kind of tree called a
btree
)
Here is the conceptual picture of a tree (of letters):
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each letter represents one
node
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the arrows from one node to another are called
edges
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the topmost node (with no incoming edges) is the
root
(node A)
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the bottom nodes (with no outgoing edges) are the
leaves
(nodes D, I, G & J)
So a (computer science) tree is kind of like an upsidedown real tree.
..
Page 1 of 6
Introduction to Trees
2008/3/27
http://pages.cs.wisc.edu/~cs3671/topics/Trees/
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path
in a tree is a sequence of (zero or more) connected nodes; for example, here are 3 of the paths in
the tree shown above:
The
length
of a path is the number of nodes in the path, e.g.:
The
height
of a tree is the length of the longest path from the root to a leaf; for the above example, the
height is 4 (because the longest path from the root to a leaf is A
→
C
→
E
→
G, or A
→
C
→
E
→
J). An
empty tree has height = 0.
The
depth
of a node is the length of the path from the root to that node; for the above example:
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the depth of J is 4
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the depth of D is 3
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the depth of A is 1
Given two connected nodes like this:
Node A is called the
parent
, and node B is called the
child
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 Spring '08
 MarvinSolomon
 Data Structures, Tree traversal, Nested set model

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