Dictionary Implementations Chapter 18 Slides by Steve Armstrong LeTourneau University Longview, TX 2007, Prentice Hall

Dictionary Implementations

Chapter 18

Slides by Steve ArmstrongLeTourneau University

Longview, TX2007,Prentice Hall

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Chapter Contents

• Array-Based Implementations An Unsorted Array-Based Dictionary A Sorted Array-Based Dictionary

• Vector-Based Implementation

• Linked Implementations An Unsorted Linked Dictionary A Sorted Linked Dictionary


Array Based Implementations 1

• Each entry consists of two parts A search key A value

• Strategies Encapsulate the two parts into an object Use two parallel arrays

Text focuses on first approach

Text focuses on first approach


Array-Based Implementations

Fig. 18-1 Two possible ways to use arrays to represent dictionary

entries: (a) an array of objects that encapsulates

each search key and corresponding value …


Array-Based Implementations

Fig. 18-1 Two possible ways to use arrays to represent dictionary entries: (b) parallel

arrays of search keys and values


Unsorted Array-Based Dictionary

• Our implementation uses one array Each element in dictionary (the array) is an

instance of class Entry Entry will be private and internal to the

dictionary class

• Outer class stated in terms of type parameters K and V Data types of the search keys and the values

• View source code of ArrayDictionary


Unsorted Array-Based Dictionary 5

Fig. 18-2 Adding a new entry to an unsorted array-based dictionary.

Click to see method add()

Click to see method add()


Unsorted Array-Based Dictionary 6

Fig 18-3 Removing an entry from an unsorted array-based dictionary

Click to see method

remove()

Click to see method

remove()


Unsorted Array-Based Implementations 8

• Unsorted worst-case efficiencies Addition O(1) Removal O(n) Retrieval O(n) Traversal O(n)


Sorted Array-Based Dictionary 9

Fig. 18-3 Adding an entry to a sorted

array-based dictionary: (a) search;

(b) make room; (c) insert.


Sorted Array-Based Dictionary 11

• Some of implementation same as unsorted dictionary

• Differences Search key must be from class that

implements Comparable

• View class SortedArrayDictionary• Note methods

add locateIndex


Sorted Array-Based Implementations 15

• Sorted worst-case efficiencies Addition O(n) Removal O(n) Retrieval O(log n) Traversal O(n)


Vector-Based Implementations

• Similar in spirit to the array-based version

• With vector no need for … makeRoom doubleArray isArrayFull

Counting entries, vector does so for you

• View class SortedVectorDictionary Note private inner class KeyIterator


Linked Implementations 22

Fig. 18-6 Three possible ways to use linked nodes to represent the entries of a dictionary: (a) a chain of nodes

that each reference an entry object; …


Linked Implementations

Fig. 18-6 Three possible ways to use linked nodes to represent the entries of a dictionary: (b) parallel chains of

search keys and values …



Fig. 18-6 Three possible ways to use linked nodes to represent the entries of a dictionary: (c) a chain of

nodes that each reference a search key and a value


Unsorted Linked Implementations 23

• Unsorted worst-case efficiencies Addition O(1) Removal O(n) Retrieval O(n) Traversal O(n)



Fig. 18-7 Adding to an unsorted linked dictionary.


A Sorted Linked Dictionary 25

• When adding nodes Requires sequential search from beginning Need only search until desiredKey ≥ nodeKey

• View class SortedLinkedDictionary• Note private inner class KeyIterator


Sorted Linked Implementations 27

• Sorted worst-case efficiencies Addition O(n) Removal O(n) Retrieval O(n) Traversal O(n)

Documents

Dictionary Implementations Chapter 18 Slides by Steve Armstrong LeTourneau University Longview, TX 2007, Prentice Hall