1. CS2468: Data Structures and Data Management
Lecturer: Lusheng Wang
Office: B6422
Phone:
TA (Assignment Marking and Tutorial)
Chao SHEN , Phone:
Zicheng ZHAO
Welcome to ask questions at ANY time.
The course Website: Canvas
Some Java Source code:
The course Website:
Text Book: Michael T. Goodrich and Roberto Tamassia, Data Structure and Algorithms in Java, John Wiley & Sons, Inc. 5th Edition
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2. Topics to be covered Analysis of Algorithms Data Structures
worst case time and space complexity
Data Structures
stack, queue, linked list, tree, priority queue, heap, hash, and graph,  
Searching algorithms
binary and AVL search trees;
Sorting algorithms
merge sort, quick sort, bucket sort and radix sort; (Reduce some contents)
Graph
data structure, depth first search and breadth first search. (add some interesting contents).
shortest path.
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3. Why This Course?
You will be able to evaluate the quality of a program (Analysis of Algorithms: Running time and memory space )
You will be able to write fast programs
You will be able to solve new problems
You will be able to give non-trivial methods to solve problems.
(Your algorithm (program) will be faster than others.)
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4. Course Evaluations Course work: 30% Final Exam: 70% Course Work:
Three assignments, 15%
One quiz or lab test 3%
One mid term exam 12%
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5. OBTL: Course Intended Learning Outcomes
1.Describe the functionality of a data structure as an abstract data type; 
2.Implement an abstract data type in a programming language; 
3.Implement and test data structures for common structures; 
4.Select an appropriate data structure from a given set of structures to solve a given problem;
 5.Design and implement data storage management with simple file structures. 
Will be tested in quiz or assignment or midterm.
For each item, you have to get 40% to pass.

6. Pre-requisites: CS2360 Java Programming /or Not known java?
Spend the rest of 8-10 days to study Java.
Read textbook p1-p53
Design a class with two integers C1 and C2 and a method f() to calculate the average value of c1 and c2.
If you cannot do that, you should worry…
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7. Data Structures Algorithms
A systematic way of organizing and accessing data. --No single data structure works well for ALL purposes.
Data stored
operation on data
Algorithms
an effective method expressed as a finite list of well-defined instructions for calculating a function. 
Algorithms are used for calculation, data processing, and automated reasoning.
In simple words an algorithm is a step-by-step procedure for calculations.
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8. How to describe algorithm?
Nature languages
Chinese, English, etc.
Not accurate.
Pseudo-code
Codes close to computer languages
Omits details that are not essential for human understanding
Intended for human reading rather than machine reading
Programs
C /C++ programs, Java programs.
Pseudo-code is preferred
Allow a well-trained programmer to be able to implement.
Allow an expert to be able to analyze the running time.
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9. An Example of an Algorithm
Algorithm sorting(X, n) Input array X of n integers Output array X sorted in a non-decreasing order for i  0 to n  1 do for j  i+1 to n-1 do if (X[i]>X[j]) then { s=X[i]; X[i]=X[j]; X[j]=s; } return X // after i-th round, the i-th smallest number is at i-th position.
Algorithm sorting(X, n)
Input array X of n integers
Output array X sorted in a non-decreasing order
for i from 0 to n  1 do
for j from i+1 to n-1 do
if X[i] is larger than X[j]
swap(X[i], X[j])
return X
// after i-th round, the i-th smallest number is at i-th position.
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10. Variables, Primitives A variable has its value Examples
A type is associated,
E.g., int, boolean, float, long, etc.
A value is assigned to the variable
The value is stored in the memory
The size of the value is determined umbigously; 64 bit machine, int 8 bytes, double 8 bytes, etc
Examples
int x;
int y=50;
char c, z=‘A’;
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11. Objects (extension of variables)
An object has both a state and behavior.
State defines the object,
Behavior defines what the object does.
What is the size of an object in the memory?

12. Class Class defines the type of an object
the kinds of operations that it performs.
A Java class uses variables to define data fields and methods to define behaviors.
A class provides a special type of methods,
known as constructors, which are invoked to construct objects from the class.

13. Classes

14. Class Diagram

15. State/attributes—variables Operation/action – methods
© 2003 Brooks/Cole Publishing / Thomson Learning™
State/attributes—variables
Operation/action – methods
Figure 2.3: Class
specification of Person

16. Figure 2.7: Providing methods to access the attributes of Person
© 2003 Brooks/Cole Publishing / Thomson Learning™
Figure 2.7: Providing
methods to access the
attributes of Person

17. Figure 2.8: An Instance fred of the Person class
© 2003 Brooks/Cole Publishing / Thomson Learning™
Figure 2.8: An
Instance fred of the
Person class

18. Figure 2.9: Using the access methods to set fred’s attributes
© 2003 Brooks/Cole Publishing / Thomson Learning™
Figure 2.9: Using the access methods
to set fred’s attributes

19. Constructors Circle() { } Circle(double newRadius) {
radius = newRadius;
Constructors are a special kind of methods that are invoked to construct objects.

20. Constructors, cont.
A constructor with no parameters is referred to as a no-arg constructor.
Constructors must have the same name as the class itself.
Constructors do not have a return type—not even void.
Constructors are invoked using the new operator when an object is created. Constructors play the role of initializing objects.

21. Creating Objects Using Constructors
new ClassName();
Example:
new Circle();
new Circle(5.0);

22. Declaring/Creating Objects in a Single Step
ClassName objectRefVar = new ClassName();
Example:
Circle myCircle = new Circle();
Assign object reference
Create an object

23. Accessing Objects Referencing the object’s data: objectRefVar.data
e.g., myCircle.radius
Invoking the object’s method:
objectRefVar.methodName(arguments)
e.g., myCircle.getArea()
Show a complete program
C7-TestCircle1.html

24. Part-B1 Stacks (p198-p213)

25. Abstract Data Types (ADTs)
an abstraction of a data structure
An ADT specifies:
Data stored
Operations on the data
Error conditions associated with operations
e.g. : ADT modeling a students record
The data stored are
Student name, id, as1, as2,as3, exam
The operations supported are
int averageAs(as1,as2,as3)
Int finalMark(as1, as2,as3, exam) )
Error conditions:
Calculate the final mark for absent student
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26. The Stack ADT (§5.1) Auxiliary stack operations:
object top()
returns the last inserted element without removing it
integer size()
returns the number of elements stored
boolean isEmpty()
indicates whether no elements are stored
The Stack ADT stores arbitrary objects
Insertions and deletions follow the last-in first-out (LIFO) scheme
Main stack operations:
push(object)
inserts an element
object pop()
removes and returns the last inserted element
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27. Applications of Stacks
Direct applications
Undo sequence in a text editor
Chain of method calls in the Java Virtual Machine
Indirect applications
Auxiliary data structure for algorithms
Component of other data structures
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28. Parentheses Matching An expression, i.e.,[(2+3)*x+5]*2.
Each “(”, “{”, or “[” must be paired with a matching “)”, “}”, or “[”
correct:
( )(( )){([( )])}
((( )(( )){([( )])}))
incorrect
)(( )){([( )])}(
({[ ])}
([)]) (
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29. Examples
Picture is from
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30. Examples ( ) ( ( ) ) { ( [ ( ) ] ) } ( ( ( ( { ( { [ ( { ( [ { [ ( { (
( ) ( ( ) ) { ( [ ( ) ] ) } ( ( ( ( { ( { [ ( { ( [ { [ ( { ( { {

31. Examples
( ) ( ( ] ) { ( [ ( ) ] ) }
Mismatch!!! ( ( ( (

32. Examples
( ) ( ( ) ) { ( [ ) ] ) }
Mismatch!!! ( ( ( ( { ( { [ ( { ( {

33. Examples ( ) ( ( ) ) { ( [ Mismatch!!! ( ( ( ( { ( { [ ( {
( ) ( ( ) ) { ( [
Mismatch!!!
(stack is non-empty) ( ( ( ( { ( { [ ( {

34. Examples
( ) ( ( ) ) )
Mismatch!!!
(pop empty stack) ( ( ( (

35. Parentheses Matching Algorithm
Algorithm ParenMatch(X,n): Input: An array X of n tokens, each of which is either a grouping symbol, a variable, an arithmetic operator, or a number Output: true if and only if all the grouping symbols in X match Let S be an empty stack for i=0 to n-1 do if X[i] is an opening grouping symbol then S.push(X[i]) else if X[i] is a closing grouping symbol then if S.isEmpty() then return false {nothing to match with} if S.pop() does not match the type of X[i] then return false {wrong type} return true {every symbol matched} else return false {some symbols were never matched}
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36. Parentheses Matching Example 1
Input: () (() [()]) i
X[i]
Operation
Stack
Output (
Push ( 1 )
Pop (
Test if ( and X[i] match? YES 2 3 (( 4
Test if ( and X[i] match? YES 5 [
Push [ ([
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37. Parentheses Matching Example 1
Input: () (() [()]) i
X[i]
Operation
Stack
Output 6 (
Push (
([( 7 )
Pop (
Test if ( and X[i] match? YES ([ 8 ]
Pop [
Test if [ and X[i] match? YES 9
Pop (
Test if ( and X[i] match? YES
Test if stack is Empty? YES
TRUE
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38. Parentheses Matching Example 2
Input: ( () [] ]() i
X[i]
Operation
Stack
Output (
Push ( 1 (( 2 )
Pop (
Test if ( and X[i] match? YES 3 [
Push [ ([ 4 ]
Pop [
Test if [ and X[i] match? YES 5
Pop (
Test if ( and X[i] match ? NO
FASLE
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39. Stack Interface in Java
public interface Stack {
public int size();
public boolean isEmpty();
public Object top() throws EmptyStackException;
public void push(Object o);
public Object pop() throws EmptyStackException; }
Java interface corresponding to our Stack ADT
Requires the definition of class EmptyStackException
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40. Exceptions
Attempting the execution of an operation of ADT may sometimes cause an error condition, called an exception
Exceptions are said to be “thrown” by an operation that cannot be executed
In the Stack ADT, operations pop and top cannot be performed if the stack is empty
Attempting the execution of pop or top on an empty stack throws an EmptyStackException
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41. Array-based Stack (Implementation)
Algorithm size()
return t + 1
Algorithm pop()
if isEmpty() then
throw EmptyStackException
else
t  t  1
return S[t + 1]
A simple way of implementing the Stack ADT uses an array
We add elements from left to right
A variable t keeps track of the index of the top element … S 1 2 t
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42. Array-based Stack (cont.)
The array storing the stack elements may become full
A push operation will then throw a FullStackException
Limitation of the array-based implementation
Not intrinsic to the Stack ADT
Algorithm push(o)
if t = S.length  1 then
throw FullStackException
else
t  t + 1
S[t]  o S 1 2 t …
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43. Array-based Stack (Cont.)
Algorithm isEmpty()
if t<0 then return true
else return false
Algorithm top()
if isEmpty() then
throw EmptyStackException
return S[t ]
A Stack might be empty
top returns the element at the top of the Stack, but does not remove the top element. When the Stack is empty, an error occurs. … S 1 2 t
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