CSC 212 Data Structures

1
CSC 212 Data Structures

• Lecture 30
• Midterm Review

2
Problem of the Day

• Can you make this equation correct by only moving
  the numbers around
• 76 24
• 72 49

3
Composing/Combining Classes

• When class has or uses another class
• Define field(s) or local(s) of latter class
• Do not use extends nor use implements
• Gives new class all functionality of original
• More than having or using certain capabilities
• I have an arm ! I am 5 fingers and a palm
• I use a fork ! I have 4 silver tines

4
Composing/Combining Classes

• When class is or includes another
• Suggests a subclass/superclass relationship
• Now use extends or implements
• Gives new class all functionality of original
• Prevents rewriting methods and automatically
  exposes functionality
• I am a bird ? I am an animal
• I am a CSC professor ? I am a geek

5
Interfaces

• Programming is already hard
• Law of Cybernetic Entomology
• There is always one more bug
• Why would we want to make it harder?
• I can only remember 3 things at once
• Want to limit complexity of my life
• Do not worry about code beyond method I am writing

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Interfaces

• Provide total abstraction of implementation
• Specifies number of public methods
• Classes must include implementation of every
  method
• Allows you to use simplified model
• Forcibly divorced from how it is implemented
• Similar to how you all use String
• In my system, takes 1000 lines of code
• Includes a HashMap!

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When To Break an Interface

• Break interface by getting actual class
• ONLY DO THIS WHEN NECESSARY!
• Only break what you make!
• Break interfaces only for objects the class
  creates
• Better to use methods in interface

8
Writing Debugging Classes

• Try limiting the amount of code to write
• Use other methods whenever possible
• Careful about replacing O(1) operation with O(n)
  method call
• Remember, writing code is hard
• Think about ways to simplify process

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Working With Linked Lists (1)
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Working With Linked Lists (2)
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Where We Are

• All these ADTs are types of Collections
• Serve similar purpose hold data for processing
• Collections usually have certain functions
• Method to add data to Collection
• Method to remove data from Collection
• Method to get datum from Collection
• Method to switch datum from Collection
• Classes differ in how to access data

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Where We Are (2)
Sequence
Collection of elementsAccess by rank
Collection of PositionsAccess via next prev
Collections of elementsAccess ends only
Deque
IndexList
PositionList
List
Queue
Stack
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Where We Are (3)

• Collections of Entrys
• Methods are named like IndexList, but
  uses the keys instead of ranks

Map
Dictionary
14
Your Turn

• Get back into groups and do activity

15
Before Next Lecture

• Keep up with your reading!
• Cannot stress this enough
• Continue Week 12 Assignment
• Read Programming Assignment 4
• Prepare for Midterm 2 next Monday
• Will also be open book, open note
• Covers from last midterm through this week