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Lecture 1

Intro

Some slides were borrowed from Josh Hug and Adam Jundt

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Reminders

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Plan for today

Introduction
Why JAVA??
Class Components (very brief)
Start an actual lecture

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About me

Marina Langlois: Marina, Dr. Langlois, Mrs. Langlois

Before UCSD:

PhD from UIC (Chicago)
Lecturer at UIC
Lecturer at Yeshiva (NYC)

At UCSD:

CSE 8A, 12, 20, 150
DSC 10, 20, 30, 80 and 95

Not working:

Having fun with my family

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Class overview

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Class Overview

Introduction to the basic data structures used in computer science:

Understand each data structure in detail
Analyze the algorithms that use them
Know limitations of each data structure

Practice designing and applying data structures to real world problems through coding.
Learn some Java as a programming language.

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Why Java for Data Science?

Java is fast

Great for developing back end of machine learning algos

Has good selection of libraries:

For ML

Understand someone else’s code
Understand terminology
Resume looks better
For this class in particular

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I am scared of Java

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In particular...

Efficiency

Good algorithms.
Good data structures.

Programming(efficiently)

Designing, building, testing, and debugging large programs.
Use of programming tools.

git, IntelliJ and JUnit

Java (not the main focus of this class)

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Why study algorithms and Data Structures?

To find a job.
To keep a job.

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Grade components:

Reading quizzes: 10%
Participation in class: 2% EXTRA CREDIT
Discussions: 4%
Programming Assignments: 36%
Two midterm exams: 20%
Final Exam: 30%

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Reading quizzes: 10%

You will have a reading assignment for each class

Check the schedule (website: DSC30.org)

Reading quizzes will be assigned for each class

Either on Canvas (3 attempts to complete it. Take the max score).
Or Zybooks. It has “activities” => will be considered as reading quizzes (demo)

Ideally be completed before each class (Deadline is Friday for all)

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Zybooks policies

If you decide to drop the class within a few weeks, zybooks gives your money back: Link
If I use it again and you have to retake the class it is either free or huge discount: Link

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Participation in class: 2% LUMVJP

I ask questions, you answer them :) using webclicker (like last quarter)
At least 70% of the questions to count.
Make sure to use your UCSD email address (i.e., @ucsd.edu) when creating an account. Only use lowercase when entering your email address.
Your password should have a length of at least 6
For student identifier, put in your PID
Make sure you are on the guest/public wifi for it to work.
Make sure your geolocation is on.

https://webclicker.web.app/

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Discussions: 4%

The purpose of discussions is to prepare you for taking exams on paper.

Process:

You will be given a few problems emulating exam questions and a limited time.
After the time is up, you will give your work to the tutor and then he/she will go over the solutions with you.
In order to record your participation, you will the weblicker app, so please bring your phones

Notes:

1 lowest discussion will be dropped.
If your exam score is above 90%, then 3 more discussions will be dropped.

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Programming Assignments (PAs): 36%

You will have ~one assignment per week (sometimes longer). Including weeks with midterms.
Write-up will on the website, I will announce it on Ed Discussion when published.
After each PA I will have a feedback form: 3 points for you PA (not EC)

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Assignments. Late submissions

You will have one assignment per week.
Write-up will be on the website

5 slip days: you can submit late within 24 hours without penalty.
Redeem: you can re-submit your HWs and get up 70% points back after the grades are released (1 week, only autograded part).

* Unless something exceptional had happened. Documentation will be required in some cases.

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Exams: 50% in total

Midterms are during the class period
You can’t skip/miss midterm unless you have a good reason.

Unless something exceptional had happened then you can make it up.

Final exam:

Gives you opportunity to replace your midterm (s) grade with the higher one.

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Collaboration

Asking questions is highly encouraged

Discuss all questions with each other (except exams and checkpoint quizzes)
Submit homeworks individually (or only with the partner when allowed), but feel free to discuss with others (general approach, the best data structure et)
Discussion: does NOT answer the question “HOW?”

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Collaboration

Asking questions is highly encouraged

Discuss all questions with each other (except exams and checkpoint quizzes)
Submit homeworks individually (or only with the partner when allowed), but feel free to discuss with others (general approach, the best data structure et)

The limits of collaboration

Don't share solutions with each other or look at someone’s code

Including Google

Academic integrity violations will result in failing the course

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ChatGPT: is it allowed?

Short Answer: No but Yes :)

NO: You can’t use it to solve the PAS. Remember the purpose of this class: practice as much as possible.

YES: One of the great advantage I see is the ability to generate questions that suit your needs.

Ask chatGPT to generate a problem without a solution.
Try to solve it.
Then ask for a solution and compare or ask for explanation. Be careful: it is wrong sometimes!

Bottom Line: Do not use PAS questions since you have nothing left to practice on for real!

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Not quite alone

Team of tutors (their zoom/lab hours will be on the calendar).

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First Java Program

“Hello World”

Wiki

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reminder

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Basic rules -1: Demo

All code in Java must be part of a class
For code to run you need to have

public static void main(String[] args)

We mark the beginning and end of segments of code using { and }
All statements in Java must end in a semi-colon: ;

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Print all numbers from 1 to 5

#print numbers from 1 to 5

x = 1

while x <= 5:

print(x)

x = x + 1

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Basic rules - 2

Before Java variables can be used, they must be declared
Java variable must have a specific type:

int, String, double, boolean etc

Types can never change
Types are verified before the code even runs

Big difference between Python and Java

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Discussion Question - 1

How many errors can you find in the code on the right?

A: 1

B: 2

C: 3

D: 4

E: 5 or more

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Functions

# defining functions�def smaller(x, y):� """ Returns smaller of the two """�� if (x < y):� return x� return y�� print(smaller(3, 4))

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Defining Functions. Basic Rules

Functions must be declared as part of a class in Java

A function that is inside a class is called a “method”
All functions in Java are methods

To define a function in Java we use “public static”

Other ways are later

All parameters must have a declared type
Return value of the function must have a declared type
Functions in Java return only one value

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Discussion Question

How many errors can you find?

A: 1

B: 2

C: 3

D: 4

E: 5 or more

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Documenting your code with Javadoc

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For loop in java

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For loop in java

What is the output? *

A: 1, 3, 5, 7, 9

B: 1, 3, 5, 7, 9, 11

C: 1, 4, 7, 10

D: 1, 4, 7

E: None of the above

* Assume that the output does not have commas and each number is on a new line.

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Main difference

You can modify “i” inside the loop and the change will be reflected in the header as well.

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Reflections on Static Typing

The Good:

�The Bad:

Talk to each other about pros and cons

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