Richard Fateman CS 282 Lecture 41 Polynomial representations Lecture 4.
Lecture 41: Course Review
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Transcript of Lecture 41: Course Review
LECTURE 41:COURSE REVIEW
CSC 212 – Data Structures
Thurs., Dec. 15th from 12:30 – 2:30PM in OM 200
Plan on exam taking full 2 hours If major problem, come talk to me ASAP
Exam covers material from entire semester Open-book & open-note so bring what
you’ve got My handouts, solutions, & computers are
not allowed Cannot collaborate with a neighbor on the
exam Problems will be in a similar style to 2
midterms
Final Exam
Inheritance
implements & extends used for relationships Both imply there exists an IS-A relationship
public class Student extends Person {…}
public class Cat extends Mammal { … }
public class AQ<E> implements Queue<E>{…}
All Java classes extend exactly 1 other class All fields & methods inherited from the
superclass Within subclass, can access non-private
members Private methods inherited, but cannot be
accessed Classes can implement any number of
interfaces Must implement methods from the
interface
Inheritance
Subclass can override/overload inherited methods Instance’s type determines which method is
called Parameter list stays the same to override the
method Overload method by modifying parameter list
Field in superclass hidden by redeclaring in subclass 2 fields with the same name now in subclass Use the field for variable’s type
Overriding & Hiding
Exceptions in Java
throw an exception when an error detected Exceptions are objects - need an instance to throw
try executing code & catch errors to handle try only when you will catch 1 or more exceptions
Do not need to catch every exception If it is never caught, program will crash Not a bad thing – had an unfixable error!
Exceptions listed in methods’ throws clause Uncaught exception only need to be listed Should list even if thrown by another method
Abstract Methods
Methods declared abstract cannot have body IOU for subclasses which will eventually
define it abstract methods only in abstract
classes Cannot instantiate an abstract class But could still have fields & (non-abstract)
methods abstract methods declared by
interfaces Interfaces cannot declare fields public abstract methods only in
interfaces
Concrete implementations used to hold data
Not ADTs Arrays are easier to use & provide
quicker access Also are impossible to grow Implementing ADTs harder due to lack of
flexibility Slower access & more complex to use
linked lists Implementing ADTs easier with increased
flexibility Can be singly, doubly, or circularly linked
Arrays vs. Linked Lists
Stack vs. Queue
Access data with Stack in LIFO order Last In-First Out is totally unfair (unless
always late) Data accessed in Queue using FIFO
order First In-First Out ensures early bird gets
the worm
Ord
er r
ead
if Q
ueue
Order read if S
tack
Queue Stack Deque
Simplest ADTs
DEQUE QUEUE STACK
addFront()addLast()
enqueue() push()
getFront()getLast()
front() top()
removeFront()removeLast()
dequeue() pop()
ADT Operations
import java.util.Iterator;import java.lang.Iterable;
public interface Iterator<E> { E next() throws NoSuchElementException; boolean hasNext(); void remove() throws UnsupportedOperationException;}
public interface Iterable<E> { Iterator<E> iterator();}
Iterators & Iterables
Abstract work in processing with IteratorIterable<Integer> myList;Iterator<Integer> it;...for (it = myList.iterator(); it.hasNext(); ) { Integer i = it.next(); ...}
Process Iterable objects in an even easier way
...for (Integer i : myList) { ...}
More Iterator & Iterable
Collection which we can access all elements Add element before an existing one Return the 3rd element in List Loop over all elements without removing
them LIST ADTs differ in how they provide
access INDEXLIST uses indices for absolution
positioning Can only use relative positions in NODELIST
All LISTS are ITERABLE
IndexList & NodeList
Sequence ADT
Combines DEQUE, INDEXLIST, & POSITIONLIST Includes all methods defined by these
interfaces Adds 2 methods to convert between
systems Get Position at index using atIndex(i) indexOf(pos) returns index of a Position
Sequence ADT
Combines DEQUE, INDEXLIST, & POSITIONLIST Includes all methods defined by these
interfaces Adds 2 methods to convert between
systems Get Position at index using atIndex(i) indexOf(pos) returns index of a Position
Trees vs. Binary Trees
Both represent parent-child relationships Both consist of single "root" node & its
descendants Nodes can have at most one parent
Root nodes are orphans -- do not have a parent
All others, the non-root nodes must have parent
Children not required for any node in the tree No limit to number of children for non-
binary trees 2 children for node in binary tree is the
maximum
Traversal Methods
Many traversals, differ in order nodes visited Do parent then do each kid in pre-order
traversal
Traversal Methods
Many traversals, differ in order nodes visited Do parent then do each kid in pre-order
traversal Post-order traversal does kids before doing
parents
Traversal Methods
Many traversals, differ in order nodes visited Do parent then do each kid in pre-order
traversal Post-order traversal does kids before doing
parents Do left kid, parent, then right kid in in-order
traversal
Tree
D
Visualization of Tree
B
DA
C E
F
B
A F
C E
Tree
root
size6
BinaryTree
Picturing Linked BinaryTree
B
CA
D
B
A C
D
BinaryTree
root
size4
Priority Queue ADT
Priority queue uses strict ordering of data Values assigned priority when added to the
queue Priorities used to process in completely
biased order
First you get the sugar,
then you get the power,
then you get the women
Priority Queue ADT
PriorityQueue yet another Collection Prioritize each datum contained in the
collection PQ is organized from lowest to highest
priority Access smallest priority only sort of like Queue min() & removeMin() return priority & value
Implementation not defined: this is still an ADT Remember that organization & order is
theoretical only
PriorityQueue yet another Collection Prioritize each datum contained in the
collection PQ is organized from lowest to highest
priority Access smallest priority only sort of like Queue min() & removeMin() return priority & value
Implementation not defined: this is still an ADT Remember that organization & order is
theoretical only
Priority Queue ADT
order is theoretical only
Entrys in a PriorityQueue
PriorityQueues use Entry to hold data As with Position, implementations may
differ Entry has 2 items that define how it
gets used PQ will only use key – the priority given to
the Entry Value is important data to be processed by
program
Sequence-based Priority Queue Simplest implementation of a Priority
Queue Instance of Sequence used to store Entrys
Many implementations possible for Sequence But we already know how to do that, so… Assume O(1) access and ignore all other
details But how to store Entrys in the Sequence? Order Entrys by priority within the Sequence
-OR- Sequence unordered & searched when
needed
Heaps
Binary-tree based PQ implementation Still structured using parent-child
relationship At most 2 children & 1 parent for each node
in tree Heaps must also satisfy 2 additional
properties Parent at least as important as its children Structure must form a complete binary tree
2
95
67
Hints for Studying
Will NOT require memorizing: ADT’s methods Node implementations Big-Oh time proofs (Memorizing anything)
You should know (& be ready to look up): How ADT implementations work (tracing &
more) For each method what it does & what it
returns Where & why each ADT would be used For each ADT implementations, its pros &
cons How to compute big-Oh time complexity
Hints for Studying
1. What does the ADT do? Where in the real-world is this found?
2. How is the ADT used? What are the applications of this ADT? How is it used and why?
3. How do we implement the ADT? Given the implementation, why do we do it
like that? What tradeoffs does this implementation
make?
Studying For the Exam
“Subtle” Hint
Do NOT bother with
memorizationBe ready to lookup &use information quickly
Final Exam Schedule
Lab Mastery Exam is:Tues., Dec. 13th from 8:00 – 10:00PM in OM 119
Final Exam is: Thur., Dec. 15th from 12:30 – 2:30PM in OM 200