CSC 212

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CSC 212 Data Structures

• Lecture 24
• Sequences and Collections

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Question of the Day

• What three letter word completes the first word
  and starts the second one
• DON ??? CAR
• Key completes the first word (donkey) and a key
  starts a car

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List ADT

• Accesses all elements in a Collection
• Can access all elements without removals
• set added to accessors and removals
• Lists are Iterable
• Provide Iterator to loop through its element
• Differ in how they provide access
• IndexList access via integer ranks
• PositionList access via relative Position
• Want method to merges approaches

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Sequences

• Combine IndexList and PositionList ADTs
• Can discuss relative location of data
• Can also use numerical ranks
• Also converts between the two
• Returns Position at a given rank
• Gets the rank for a given Position

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Sequence Interface

• public interface SequenceltGgt extends
  IndexListltGgt, PositionListltGgt,
  DequeltGgt public PositionltGgt atRank(int r)
  throws BoundaryViolationExceptionpublic int
  rankOf(PositionltGgt p) throws InvalidPositionExcept
  ion
• Includes all methods from 3 interfaces
• Converts between rank and Position
• Implementation still not defined
• But must include Positions

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Sequences Applications

• Basic, general-purpose, data structure
• Useful for storing collection of elements
• Collections can be ordered or unordered
• Often used as basis of other data structures
• Can be used to implement stack, queue, deque, or
  list
• Also used for small, simple databases
• Basic building block of many other structures
• Many (though not all) use a Sequence somewhere
• Javas collections are derived from Sequences

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Linked list-based Sequence

• May/may not use special header trailer nodes
• Node class implements Position
• Position-based calls run in constant time
• Rank-based methods search through list

Nodes/Positions
elements
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Array-based Sequence
elements

• Use array in circular manner
• Array entries contains class
• Implements Position
• Also stores rank

0
1
2
3
positions
S
l
f
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Your Turn

• Get back into groups and do activity

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Before Next Lecture

• Keep up with your reading!
• Continue Week 10 Assignment
• Work on Programming Assignment 2