22C:21 Problem 4.3

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22C21 Problem 4.3

• Solution Outline

2
Trie

• Store characters in each node, not keys
• Use characters of the key to guide the search
  process
• From retrieval, but pronounced try

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Example
g
s
t
i
o
u
h
go
m
e
n
she
Make sure the word she is not found unless
it has been explicitly inserted!
sun
d
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shed
time
l
shell
4
Applications

• Spell checkers
• Data compression
• Computational biology
• Routing tables for IP addresses
• Storing/Querying XML documents
• and many other

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Building block - Class Node
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Class Trie

• Specify root node
• Insert method
• public void insert (String s)
• Search method
• public boolean search (String s)

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T.insert(tick)
g
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go
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sun
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shed
time
tick
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shell
place a marker
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T.insert(tick)
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tick
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T.search(group)
g
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o
null
u
h
Failure return false
go
m
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n
sun
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shed
time
tick
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T.search(timer)
g
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go
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sun
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shed
time
tick
l
Failure return false
null
shell
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T.search(she)
g
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go
m
c
e
n
String found. But no marker!
sun
Failure return false
d
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k
shed
time
tick
l
shell
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T.search(shed)
g
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go
m
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sun
String found. Marker found!
d
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shed
time
tick
Success return true
l
shell
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Quiz 4 Problem 4.2

• Draw a trie corresponding to the collection of
  words
• abacus, abode, dreaded, dust, dusty, planar,
  east
• Write a main() method that defines a trie and
  performs successive insertions of the above
  strings.