15-121 Introduction to Data Structures 1 September 2020 Margaret Reid-Miller
Today • Course Logistics • Course Topics • A (very basic) Java introduction • Course website: https://www.cs.cmu.edu/~mrmiller/15-121 Fall 2020 15-121 (Reid-Miller) 2
Me Margaret Reid-Miller mrmiller@cs.cmu.edu Gates 6003, x 8-2640 I am an Assistant Teaching Professor • CS Upperclass Academic Advisor • What to call me? Margaret, please (or formally, Professor Reid-Miller) Fall 2020 15-121 (Reid-Miller) 3
You • Take 15-121 if you are an IS major, or if you don’t plan to take CS core courses. • Take 15-122 if you are a CS or ECE major or minor, or plan to take more CS classes. • Why learn Java? • One of the most common languages used in industry. • Used for large applications • It's objected-oriented. Fall 2020 15-121 (Reid-Miller) 4
Office Hours For extra help on the class material or assignments you may reach out to our two Teaching Assistants or me. Office Hours: (tentatively) Sean Tavares (TA): Saturday 2:00 pm – 4:00 pm Leah Watko (TA): Sunday 2:00 pm – 4:00 pm Margaret: Monday 10:00 am – 12:00pm (noon) Other times by appointment Assignments are due Monday nights. What office-hour times are best for you? Fall 2020 15-121 (Reid-Miller) 6
OHQueue • During office hours, when you have a question open your personal Zoom meeting. • Go to the OHQueue (see webpage sidebar) and select 15-121 P (not 15-121 Q). It may be the last in the list. • (You can pin 15-121 P to the top of the list by clicking the red asterisk.) • Include a link to your Zoom meeting in the Question part. • When it is your turn a TA or I will join your Zoom meeting to help you. Fall 2020 15-121 (Reid-Miller) 7
Prerequisites • Formally: 15-112 • You will need: • Laptop or desktop computer • The Java JDK and an editor or IDE – Eclipse (what I will use in class) – DrJava (only runs Java 6 on Mac) Under Resource, see Extra Help for instructions on how to install Java JDK and Eclipse Fall 2020 15-121 (Reid-Miller) 8
Why Data Structures? Data structures are ways to organize and store data and perform operations on the data efficiently. • Understand and create new algorithms • Analyze algorithms (time/space efficiency) • Which data structures we use will depend on • What operations we expect to perform often on our data. • What are performance tradeoffs for access/update. • Efficient algorithms are essential with big data. (Think Google, databases, Amazon, Facebook,…) Fall 2020 15-121 (Reid-Miller) 9
Introduction to Data Structures • This course provides a foundation for organizing large data sets for efficiency. Two parts: • Conceptual information about various data structures • How to use and implement those data structures in your programs. • We assume you know how to write programs using fundamental programming concepts (variables, booleans, conditional, loops, functions, lists, …) Fall 2020 15-121 (Reid-Miller) 10
Course elements • Lectures: Notes and code will be posted to website • Participation – 5% • Recitation labs – 5% • Quizzes – 10% • Homework – 40% • 2 Midterms – 20%: 10% each • Final – 20% Fall 2020 15-121 (Reid-Miller) 11
Lectures over Zoom • Recordings will be put on Canvas • Be prepared to take notes, and have paper and pen/pencil. I often ask you to write code or draw figures, and may ask you to turn in what you write. • Answer and ask lots of questions (It helps your classmates who are equally curious and it gives me feedback.) Fall 2020 15-121 (Reid-Miller) 12
Participation 5% • You must attend lectures, ask questions, and submit in-class exercises. • If you miss a couple of days of class, you may still earn 100% for participation. • If you miss class half the time, you will earn 0% for participation. • If attending lectures synchronously is difficult, please email me to make alternative arrangements. Fall 2020 15-121 (Reid-Miller) 13
Wednesday Recitations 5% • In person and remote • There will be (~12) weekly labs of short coding exercises. Only 10 count towards your grade. • You must attend and participate to get credit. • You are encouraged to work collaboratively. • Submitting after class will not be accepted. • I will post solutions after class. Tomorrow’s recitation, though, will be a lecture! Fall 2020 15-121 (Reid-Miller) 14
Homework 40% • There will be weekly assignments that include a written portion and programming. • Due Monday nights at 11:59 pm. • You are allowed up to 4 late days total without penalty, with a maximum of 2 late days per assignment. • No credit will be given for late work after you have used up all your late days. • I recommend you submit often (even if incomplete) one day before and again one hour before its due. Fall 2020 15-121 (Reid-Miller) 15
Quizzes 10% • Most weeks on Thursday there will be short quiz (15-20 minutes). • It will test the previous week’s work. • We will drop your lowest TWO quizzes. • There will be no make-up quizzes for any reason. Fall 2020 15-121 (Reid-Miller) 16
2 Written Midterms 10% each • Midterm Exams will be in class on • Thursday, Oct 8 • Tuesday, Nov 9 (Dates may change, see schedule) • No makeup exams except by prior approval by me for • medical or family emergencies • pre-arranged university-approved absences Fall 2020 15-121 (Reid-Miller) 17
Final Exam 25% • During final exams. • We will not proctor the final exam prior to the registrar scheduled exam (makeup day is Dec 21). Fall 2020 15-121 (Reid-Miller) 18
Disabilities • If you suspect or have a documented disability, you may be eligible to receive accommodations from the Office of Disability Resources (access@andrew.cmu.edu) • Please use their online system to notify me and to discuss your needs early in the semester. Fall 2020 15-121 (Reid-Miller) 19
Today ü Course Logistics ➤ Overview of Course • A (very basic) Java introduction Fall 2020 15-121 (Reid-Miller) 20
Course Topics • Java Objects, Arrays, ArrayLists, Efficiency • Big-O, Linked Lists, Recursion, • Interfaces, Iterators, Stacks & Queues • Searching & Sorting, Trees, BSTs, Recursion • Sets & Maps, Hashing, Priority Queues, • Heaps, (Graphs), Review & Final Exam Fall 2020 15-121 (Reid-Miller) 21
The image part with relationship ID rId3 was not found in the file. Today ü Course Administration ü Overview of Course ➤ A (very basic) Java introduction Fall 2020 15-121 (Reid-Miller) 22
Executing Code Java and Python are high-level programming languages • (human readable) created in a text editor. • Programs in high-level languages ( source code ) cannot be run by the computer directly. Program translation converts source code to a low-level • target language . • This target or machine code uses only a small set of instructions specific to the machine. Run-time is the period when the computer is executing • commands. • The operating system copies the machine code from disk to memory and starts running it directly . Fall 2020 15-121 (Reid-Miller) 23
Program Translation • Compiler is a program that translates code in a high- level source language, all at once, into low-level target language. • E.g., Java is compiled to bytecode . • The source code is translated only once. • The target code can be executed many times. • Interpreter - program that translates each statement and then executes it, one at a time, much like a human interpreter • E.g., Python is interpreted, also to bytecode Fall 2020 15-121 (Reid-Miller) 24
Traditional Compilation Different hardware/operating systems need slight variants of each program and separate compilers. Source code Source code Source code Source code compile Machine Machine Machine Machine code code code code Linux Mac OS X Windows Linux IBM iMac Intel HP Fall 2020 15-121 (Reid-Miller) 25
Java Translation Java compiles to a single “virtual” machine. Game.java Compile Game.class (bytecode) JVM JVM JVM JVM (or compile) Interpret Windows Linux Linux Mac OS X Intel HP IBM iMac JVM - Java Virtual Machine Fall 2020 15-121 (Reid-Miller) 26
Types of Programming Errors • Compile-time errors - Syntax errors found by the compiler or syntax-aware editors (e.g., Eclipse). • e.g., x - * y = • Run-time errors - Error causes program to stop abnormally; often called an exception. • e.g., x = y / z (What if z is zero?) • Logical errors - Program produces incorrect results without complaint. • e.g., Sort program that runs to completion but does not always sort the data Fall 2020 15-121 (Reid-Miller) 27
Java vs Python Syntax • In Python, indentation is semantic (has meaning) • E.g., indentation delimits statement blocks • In Java, indentation is recommended • We require it in this class, however, for style and readability. • Instead, in Java statement blocks are surrounded by curly braces {} and most statements end in semi-colons . Fall 2020 15-121 (Reid-Miller) 28
Java program structure • Every Java program consists of one or more classes : • Each class contains methods : – Each method contains the statements to execute • Everything is Java must have a type. • Every Java program starts its execution at a method called main . Fall 2020 15-121 (Reid-Miller) 29
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