CS 340 DATA STRUCTURESInstructor: Xenia Mountrouidou

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Who am I?• Dr. X – Computer Scientist• PhD at North Carolina State University – Optical networks

performance • Worked for IBM – Software Performance Engineer• Post doc at College of William and Mary• Scuba diver, manga comics collector, science fiction

reader.

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Who am I?

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Course Objectives• At the end of this class you will be able to:

• Make design decisions on which data structure is best to use regarding • performance, • memory, and • implementation efficiency.

• Devise or use the most efficient algorithm in your projects.• Understand algorithmic complexity.• Think analytically and identify complexity of a program.

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Course Objectives (cont.)• At the end of this class you will be able to:

• Apply object oriented programming principles when you develop software.

• Use and understand third party code.• Detect inefficiency of data structures and algorithms of third party

code.• Develop projects using agile test driven approach (Junit).• Employ the Java API.

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Why do you need CS 340?• Scenario:

• You are a senior developer for Amazon. • You are working on their e-commerce application server!• You are a java guru, OO programming is second nature to you…

but you do not understand data structures and algorithms.• BIG DEAL! Everything runs perfectly. Until one day…• You need to use a sorting algorithm to sort all potential sellers of a

product based on price or ranking or relevance.

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Why do you need CS 340?• Scenario (cont.):

• On every click for a product search, your sorting algorithm will be used.

• You choose bubble sort. After all, it has a cool name!• Let’s see what happens:• http://www.sorting-algorithms.com/

Software is not just coding… It is design, performance, memory consumptionIt is an art, a riddle to be solved with every project

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More motivation• Social networks

• Do you know which data structures FB developers are using?• Which data structure is better to use for a social network?

• Do you know how Google search works?• What is the best algorithm and why?• Do they use any data structures?

• Have you heard about Big Data?

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Lectures• We meet at 11:00-12:45, every Tues/Thurs, at Merritt

Penticoff Science Bld, Room 116A• Check the schedule on the class webpage• Reading and examples will be posted online• Lectures will be interactive. This means:

• You will need to study the new material before every lecture (slides and book or online material)

• We will have a lab every week, you will need to code• You will have a test every week:

• A couple of questions on last week’s topics • A couple of questions about current week’s topics

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Lectures• I will not talk more than half an hour (hopefully!)• During lectures I will demonstrate coding• Your questions are important!• However, you should not interrupt the flow of class• I will have specific slides/time during lecture or coding

when you can ask questions

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Electronic Devices• You may use your laptop to take notes and complete

programming assignments during class• You will use the classroom computers to take tests• Smart phones will be on silent mode during class time• You may record the lectures

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QUESTIONS?

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How to get help• Join my office hours at MP 203 (2nd floor)

• Monday 1:00 - 3:00 pm, • Tuesday 9:00-11:00 am, and • Thursday 1:00-2:00 pm

• Use the tutoring sessions at the CS Society meetings (schedule will be announced soon)

• Use the tutor’s office hours (schedule will be announced soon)• Set an appointment with me via e-mail(xmountr at ju.edu)• Use the textbooks:

• Data Structures and Algorithm Analysis in Java, Mark Allen Weiss, 3rd Edition, Pearson

• Thinking in Java, Bruce Eckel, 3rd Edition. Free E-Book and textbook website.

• Experiment with code. It’s fun…

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GradingFinal exam 25%

Homework 20%

Programming projects 30%

Tests 25%

Total 100%

Homework and Programming Projects will be posted online on BlackBoard and on the class website

You will upload your completed assignments on BlackBoard

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Programming Projects• They involve

• Data Structures & Algorithms• Design• Coding• Testing• Debugging

• These will be done in pairs• You need to send me an e-mail until the end of the second

week of classes with your team members• I will assign teams if you do not find a team

• Each team member will evaluate his/her team mate• Each team member will contribute equally to coding,

design, and testing

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Homework• It will involve:

• Analytical thinking• Computational thinking• A little bit of math

• Homework will be completed individually

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Policies• Cheating means “submitting, without proper attribution, any

computer code that is directly traceable to the computer code written by another person.”

• Or even better:• “Any form of cheating, including concealed notes during exams, copying or

allowing others to copy from an exam, students substituting for one another in exams, submission of another person’s work for evaluation, preparing work for another person’s submission, unauthorized collaboration on an assignment, submission of the same or substantially similar work for two courses without the permission of the professors. Plagiarism is a form of Academic Misconduct that involves taking either direct quotes or slightly altered, paraphrased material from a source without proper citations and thereby failing to credit the original author. Cutting and pasting from any source including the Internet, as well as purchasing papers, are forms of plagiarism.”

• I give students a failing homework grade for any cheating. • A second cheating attempt will be escalated

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Policies• You may discuss homework problems with classmates,

after you have made a serious effort in trying the homework on your own.

• You can use ideas from the literature (with proper citation).

• You can use anything from the textbooks/notes.• The code you submit must be written completely by

you.

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Policies• Read the collaboration policy carefully.• Late policy:

• 1% is reduced by every day the homework is late

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Principles of Pair Programming

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Principles of Pair Programming• All I Really Need to Know about pair programming I

Learned in Kindergarten• Share everything.• Play fair.• Don’t hit people.• Put things back where you found them.• Clean up your own mess.• Don’t take things that aren’t yours.• Say you’re sorry when you hurt somebody.

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Principles of Pair Programming• Wash your hands before you eat.• Flush.• Warm cookies and cold milk are good for you.• Live a balanced life – learn some and think some and draw and

paint and sing and• Dance and play and work every day some.• Take a nap every afternoon.• When you go out into the world, watch out for traffic, hold hands

and stick together.• Be aware of wonder.

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Programming languages… a bit of history

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Programming Language Evolution• 1st generation: Machine language • 2nd generation: Assembler• 3rd generation: COBOL, FORTRAN, C, ALGOL,

BASIC, C, C++, C#, Pascal, Ada and … Java• 4th generation: SQL, spreadsheets, Mathematica,

MATLAB, SAS • 5th generation: (example, anyone?)

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Why So Many Languages?• Bring the language “closer” to the problem.• But 4GLs are typically focused on specialized domains

(e.g., relational databases).• We want a language that is general purpose, yet can

easily be “tailored” to any domain.

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QUESTIONS?

Java vs C#

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Java vs C#• Not so different from each other

• C# versus Java : syntactic differences• C# versus Java : a developer's perspective

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Java vs C#: Program StructureJava C#

package hello;

public class HelloWorld { public static void main(String[] args) { String name = "Java"; // See if an argument was passed from the command line if (args.length == 1) name = args[0];

System.out.println("Hello, " + name + "!"); } }

using System;

namespace Hello { public class HelloWorld { public static void Main(string[] args) { string name = "C#";

// See if an argument was passed from the command line if (args.Length == 1) name = args[0];

Console.WriteLine("Hello, " + name + "!"); } } }

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Java vs C#: CommentsJava C#

// Single line/* Multiple line *//** Javadoc documentation comments */

// Single line/* Multiple line *//// XML comments on a single line /** XML comments on multiple lines */

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Java vs C#: Data TypesJava C#

Primitive Types boolean byte char short, int, long float, double

Reference Types Object (superclass of all other classes) Stringarrays, classes, interfaces

Value Types bool byte, sbyte char short, ushort, int, uint, long, ulong float, double, decimalstructures, enumerations

Reference Types object (superclass of all other classes) stringarrays, classes, interfaces, delegates

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Java vs C#: Data TypesJava C#

Conversions

// int to String int x = 123; String y = Integer.toString(x); // y is "123"

// String to int y = "456"; x = Integer.parseInt(y); // x is 456

// double to int double z = 3.5; x = (int) z; // x is 3 (truncates decimal)

Conversions

// int to string int x = 123; String y = x.ToString(); // y is "123"

// string to int y = "456"; x = int.Parse(y); // or x = Convert.ToInt32(y);

// double to int double z = 3.5; x = (int) z; // x is 3 (truncates decimal)

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Java vs C#: ConstantsJava C#

// May be initialized in a constructor final double PI = 3.14;

const double PI = 3.14;

// Can be set to a const or a variable. //May be initialized in a constructor. readonly int MAX_HEIGHT = 9;

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Java vs C#: OperatorsJava C#

Comparison == < > <= >= !=

Arithmetic + - * / % (mod) / (integer division if both operands are ints) Math.Pow(x, y)

Assignment = += -= *= /= %= &= |= ^= <<= >>= >>>= ++ --

Bitwise & | ^ ~ << >> >>>

Comparison == < > <= >= !=

Arithmetic + - * / % (mod) / (integer division if both operands are ints) Math.Pow(x, y)

Assignment = += -= *= /= %= &= |= ^= <<= >>= ++ --

Bitwise & | ^ ~ << >>

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Java vs C#: OperatorsJava C#

Logical && || & | ^ !

Note: && and || perform short-circuit logical evaluations

String Concatenation +

Logical && || & | ^ !

Note: && and || perform short-circuit logical evaluations

String Concatenation +

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QUESTIONS?

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Java vs C#: ChoicesJava C#

greeting = age < 20 ? "What's up?" : "Hello";

if (x < y) System.out.println("greater");

if (x != 100) { x *= 5; y *= 2; } else z *= 6;

greeting = age < 20 ? "What's up?" : "Hello";

if (x < y) Console.WriteLine("greater");

if (x != 100) { x *= 5; y *= 2; } else z *= 6;

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Java vs C#: ChoicesJava C#

int selection = 2;switch (selection) { // Must be byte, short, int, char, or enum case 1: x++; // Falls through to next case if no break case 2: y++; break; case 3: z++; break; default: other++; }

string color = "red";switch (color) { // Can be any predefined type case "red": r++; break; // break is mandatory; no fall-through case "blue": b++; break; case "green": g++; break; default: other++; break; // break necessary on default }

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Java vs C#: LoopsJava C#

while (i < 10) i++;

for (i = 2; i <= 10; i += 2) System.out.println(i);

do i++; while (i < 10);

for (int i : numArray) // foreach construct sum += i;

while (i < 10) i++;

for (i = 2; i <= 10; i += 2) Console.WriteLine(i);

do i++; while (i < 10);

foreach (int i in numArray) sum += i;

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Java vs C#: LoopsJava C#

// for loop can be used to iterate through any Collection import java.util.ArrayList; ArrayList<Object> list = new ArrayList<Object>();list.add(10); // boxing converts to instance of Integerlist.add("Bisons");list.add(2.3); // boxing converts to instance of Double

for (Object o : list) System.out.println(o);

// foreach can be used to iterate through any collection using System.Collections; ArrayList list = new ArrayList(); list.Add(10); list.Add("Bisons"); list.Add(2.3);

foreach (Object o in list) Console.WriteLine(o);

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Java vs C#: ArraysJava C#

int nums[] = {1, 2, 3}; or int[] nums = {1, 2, 3};for (int i = 0; i < nums.length; i++) System.out.println(nums[i]);

String names[] = new String[5]; names[0] = "David";

float twoD[][] = new float[rows][cols]; twoD[2][0] = 4.5;

int[][] jagged = new int[3][]; jagged[0] = new int[5]; jagged[1] = new int[2]; jagged[2] = new int[3]; jagged[0][4] = 5;

int[] nums = {1, 2, 3};for (int i = 0; i < nums.Length; i++) Console.WriteLine(nums[i]);

string[] names = new string[5]; names[0] = "David";

float[,] twoD = new float[rows, cols]; twoD[2,0] = 4.5f;

int[][] jagged = new int[3][] { new int[5], new int[2], new int[3] };

jagged[0][4] = 5;

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Java vs C#: FunctionsJava C#

// Return single valueint Add(int x, int y) { return x + y; }

int sum = Add(2, 3);

// Return no valuevoid PrintSum(int x, int y) { System.out.println(x + y); }

PrintSum(2, 3);

// Return single valueint Add(int x, int y) { return x + y; }

int sum = Add(2, 3);

// Return no valuevoid PrintSum(int x, int y) { Console.WriteLine(x + y); }

PrintSum(2, 3);

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Java vs C#: FunctionsJava C#

// Primitive types and references are always passed by valuevoid TestFunc(int x, Point p) { x++; p.x++; // Modifying property of the object p = null; // Remove local reference to object }

class Point { public int x, y; }

Point p = new Point(); p.x = 2; int a = 1; TestFunc(a, p); System.out.println(a + " " + p.x + " " + (p == null) ); // 1 3 false

// Pass by value (default), in/out-reference (ref), and out-reference (out) void TestFunc(int x, ref int y, out int z, Point p1, ref Point p2) { x++; y++; z = 5; p1.x++; // Modifying property of the object p1 = null; // Remove local reference to object p2 = null; // Free the object }

class Point { public int x, y; }

Point p1 = new Point(); Point p2 = new Point(); p1.x = 2; int a = 1, b = 1, c; // Output param doesn't need initializing TestFunc(a, ref b, out c, p1, ref p2); Console.WriteLine("{0} {1} {2} {3} {4}", a, b, c, p1.x, p2 == null); // 1 2 5 3 True

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Java vs C#: FunctionsJava C#

// Accept variable number of arguments int Sum(int ... nums) { int sum = 0; for (int i : nums) sum += i; return sum; }

int total = Sum(4, 3, 2, 1); // returns 10

// Accept variable number of arguments int Sum(params int[] nums) { int sum = 0; foreach (int i in nums) sum += i; return sum; }

int total = Sum(4, 3, 2, 1); // returns 10

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Java vs C#: StringsJava C#

// String concatenationString school = "Harding "; school = school + "University"; // school is "Harding University"

// String comparison String mascot = "Bisons"; if (mascot == "Bisons") // Not the correct way to do string comparisons if (mascot.equals("Bisons")) // true if (mascot.equalsIgnoreCase("BISONS")) // true if (mascot.compareTo("Bisons") == 0) // true

System.out.println(mascot.substring(2, 5)); // Prints "son"

// String concatenationstring school = "Harding "; school = school + "University"; // school is "Harding University"

// String comparison string mascot = "Bisons"; if (mascot == "Bisons") // true if (mascot.Equals("Bisons")) // true if (mascot.ToUpper().Equals("BISONS")) // true if (mascot.CompareTo("Bisons") == 0) // true

Console.WriteLine(mascot.Substring(2, 3)); // Prints "son"

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Java vs C#: StringsJava C#

// My birthday: Oct 12, 1973 java.util.Calendar c = new java.util.GregorianCalendar(1973, 10, 12); String s = String.format("My birthday: %1$tb %1$te, %1$tY", c);

// Mutable string StringBuffer buffer = new StringBuffer("two "); buffer.append("three "); buffer.insert(0, "one "); buffer.replace(4, 7, "TWO"); System.out.println(buffer); // Prints "one TWO three"

// My birthday: Oct 12, 1973 DateTime dt = new DateTime(1973, 10, 12); string s = "My birthday: " + dt.ToString("MMM dd, yyyy");

// Mutable string System.Text.StringBuilder buffer = new System.Text.StringBuilder("two "); buffer.Append("three "); buffer.Insert(0, "one "); buffer.Replace("two", "TWO"); Console.WriteLine(buffer); // Prints "one TWO three"

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QUESTIONS?

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Java vs C#: Exception HandlingJava C#

// Must be in a method that is declared to throw this exception Exception ex = new Exception("Something is really wrong."); throw ex;

try { y = 0; x = 10 / y; } catch (Exception ex) { System.out.println(ex.getMessage()); } finally { // Code that always gets executed }

Exception up = new Exception("Something is really wrong."); throw up; // ha ha

try { y = 0; x = 10 / y; } catch (Exception ex) { // Variable "ex" is optional Console.WriteLine(ex.Message); } finally { // Code that always gets executed }

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Java vs C#: NamespacesJava C#

package harding.compsci.graphics;

// Import single classimport harding.compsci.graphics.Rectangle;

// Import all classesimport harding.compsci.graphics.*;

namespace Harding.Compsci.Graphics { ... }

or

namespace Harding { namespace Compsci { namespace Graphics { ... } } } // Import single classusing Rectangle = Harding.CompSci.Graphics.Rectangle;

// Import all classusing Harding.Compsci.Graphics;

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Java vs C#: Classes / InterfacesJava C#

Accessibility keywords public private protected static

// Inheritanceclass FootballGame extends Competition { ... }

Accessibility keywords public private internal protected protected internal static

// Inheritanceclass FootballGame : Competition { ... }

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Java vs C#: Classes / InterfacesJava C#

// Interface definitioninterface IAlarmClock { ... }

// Extending an interface interface IAlarmClock extends IClock { ... }

// Interface implementationclass WristWatch implements IAlarmClock, ITimer { ... }

// Interface definitioninterface IAlarmClock { ... }

// Extending an interface interface IAlarmClock : IClock { ... }

// Interface implementationclass WristWatch : IAlarmClock, ITimer { ... }

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Java vs C#: Constructors / DestructorsJava C#

class SuperHero { private int mPowerLevel;

public SuperHero() { mPowerLevel = 0; }

public SuperHero(int powerLevel) { this.mPowerLevel= powerLevel; }

// No destructors, just override the finalize method protected void finalize() throws Throwable { super.finalize(); // Always call parent's finalizer } }

class SuperHero { private int mPowerLevel;

public SuperHero() { mPowerLevel = 0; }

public SuperHero(int powerLevel) { this.mPowerLevel= powerLevel; }

~SuperHero() { // Destructor code to free unmanaged resources. // Implicitly creates a Finalize method. } }

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Java vs C#: ObjectsJava C#

SuperHero hero = new SuperHero();

hero.setName("SpamMan"); hero.setPowerLevel(3);

hero.Defend("Laura Jones"); SuperHero.Rest(); // Calling static method

SuperHero hero2 = hero; // Both refer to same object hero2.setName("WormWoman"); System.out.println(hero.getName()); // Prints WormWoman

hero = null; // Free the object

if (hero == null) hero = new SuperHero();

Object obj = new SuperHero(); System.out.println("object's type: " + obj.getClass().toString()); if (obj instanceof SuperHero) System.out.println("Is a SuperHero object.");

SuperHero hero = new SuperHero();

hero.Name = "SpamMan"; hero.PowerLevel = 3;

hero.Defend("Laura Jones"); SuperHero.Rest(); // Calling static method

SuperHero hero2 = hero; // Both refer to same object hero2.Name = "WormWoman"; Console.WriteLine(hero.Name); // Prints WormWoman

hero = null; // Free the object

if (hero == null) hero = new SuperHero();

Object obj = new SuperHero(); Console.WriteLine("object's type: " + obj.GetType().ToString()); if (obj is SuperHero) Console.WriteLine("Is a SuperHero object.");

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Java vs C#: PropertiesJava C#

private int mSize;

public int getSize() { return mSize; } public void setSize(int value) { if (value < 0) mSize = 0; else mSize = value; }

int s = shoe.getSize(); shoe.setSize(s+1);

private int mSize;

public int Size { get { return mSize; } set { if (value < 0) mSize = 0; else mSize = value; } }

shoe.Size++;

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Java vs C#: Console I/OJava C#

java.io.DataInput in = new java.io.DataInputStream(System.in); System.out.print("What is your name? "); String name = in.readLine(); System.out.print("How old are you? "); int age = Integer.parseInt(in.readLine()); System.out.println(name + " is " + age + " years old.");

int c = System.in.read(); // Read single char System.out.println(c); // Prints 65 if user enters "A"

// The studio costs $499.00 for 3 months. System.out.printf("The %s costs $%.2f for %d months.%n", "studio", 499.0, 3);

// Today is 06/25/04 System.out.printf("Today is %tD\n", new java.util.Date());

Console.Write("What's your name? "); string name = Console.ReadLine(); Console.Write("How old are you? "); int age = Convert.ToInt32(Console.ReadLine());Console.WriteLine(name + " is " + age + " years old.");

int c = Console.Read(); // Read single char Console.WriteLine(c); // Prints 65 if user enters "A"

// The studio costs $499.00 for 3 months. Console.WriteLine("The {0} costs {1:C} for {2} months.\n", "studio", 499.0, 3);

// Today is 06/25/2004 Console.WriteLine("Today is " + DateTime.Now.ToShortDateString());

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Java vs C#: File I/OJava C#

import java.io.*;

// Character stream writingFileWriter writer = new FileWriter("c:\\myfile.txt");

writer.write("Out to file.\n"); writer.close();

// Character stream readingFileReader reader = new FileReader("c:\\myfile.txt");BufferedReader br = new BufferedReader(reader); String line = br.readLine(); while (line != null) { System.out.println(line); line = br.readLine(); } reader.close();

using System.IO;

// Character stream writingStreamWriter writer = File.CreateText("c:\\myfile.txt"); writer.WriteLine("Out to file."); writer.Close();

// Character stream readingStreamReader reader = File.OpenText("c:\\myfile.txt"); string line = reader.ReadLine(); while (line != null) { Console.WriteLine(line); line = reader.ReadLine(); } reader.Close();

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QUESTIONS?

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References• C# versus Java : syntactic differences http://

www.harding.edu/fmccown/java_csharp_comparison.html