CS 332: Elements of the Theory of Computation, Spring 2020

Course Overview

This course is an introduction to the theory of computation. This is the branch of computer science that aims to understand which problems can be solved using computational devices and how efficiently those problems can be solved. To be able to make precise statements and rigorous arguments, computational devices are modeled using abstract mathematical "models of computation." The learning objectives of the course are to:
Instructor:   Mark Bun, mbun [at] bu [dot] edu
Instr. Office Hours:   Thu 5:00-6:00 (MCS 114)
    Fri 10:00-11:00 (MCS 114)
Teaching Fellow:   Nadya Voronova, voronova [at] bu [dot] edu
TF Office Hours:   Fri 2:30-4:30 (MCS B30)
Class Times:   Mon, Wed 2:30-3:45 (CAS B18)
Discussion Sections:   Tue 9:30-10:20 (FLR 121)
  Tue 11:15-12:05 (FLR 121)
  Tue 12:30-1:20 (FLR 121)

Important Links

Course Website: https://cs-people.bu.edu/mbun/courses/332_S20. The website contains the course syllabus, schedule with assigned readings, homework assignments, and other course materials.

Piazza: https://piazza.com/bu/spring2020/cs332. All class announcements will be made through Piazza, so please set your notifications appropriately. Please post questions about the course material to Piazza instead of emailing the course staff directly. It is likely that other students will have the same questions as you and may be able to provide answers in a more timely fashion. Active participation on Piazza may add extra points to your participation grade.

Gradescope: https://gradescope.com. Sign up for a student account on Gradescope using your BU email address. The entry code for the course is MKB65D. Homework assignments are to be submitted to Gradescope in PDF format.

Top Hat: https://app.tophat.com/e/400708. We will be using the Top Hat classroom response system in class. The entry code for the course is 400708. You will be able to submit answers to in-class questions using Apple or Android smartphones and tablets, laptops, or through text message.

You can visit the Top Hat Overview (Top-Hat-Overview-and-Getting-Started-Guide) within the Top Hat Success Center which outlines how you will register for a Top Hat account, as well as providing a brief overview to get you up and running on the system.

Anonymous feedback: You can send Mark anonymous feedback here at any time. He will be the only one to read it. Include your name if you would like a response.

Catalog Description

The basic concepts of the theory of computation are studied. Topics include models of computation, polynomial time, Church's thesis; universal algorithms, undecidability and intractability; time and space complexity, nondeterminism, probabilistic computation and reductions of computational problems.


CS 131 (Combinatoric Structures) and CS 330 (Introduction to Algorithms). If you have not completed the prerequisites for the course, please schedule a meeting with me before registering.

Course Outline

(Perpetually Tentative) Schedule

Date Topics Reading/Reference Handouts/Assignments
Wed 1/22 Welcome, introduction Sipser 0-1.1, L01-ann Collaboration and Honesty Policy, Math & Algorithms Review, Automata Tutor
Mon 1/27 Finite automata, regular operations Sipser 1.1-1.2, L02, L02-ann HW1 out
Wed 1/29 DFA-NFA equivalence, closure under regular operations Sipser 1.1-1.2, L03, L03-ann
Mon 2/3 Non-regular languages, Pumping Lemma Sipser 1.4, L04, L04-ann HW1 due; HW2 out
Wed 2/5 Regular expressions Sipser 1.3, L05, L05-ann
Mon 2/10 Regular expressions cont'd, context-free grammars, Pumping Lemma for CFGs Sisper 2.1, 2.3, L06, L06-ann HW2 due; HW3 out
Wed 2/12 Pushdown automata Sipser 2.2, L07, L07-ann Practice Midterm 1 distributed in class
Tue 2/18 Equivalence of PDAs and CFGs Sipser 2.2, L08, L08-ann (Tue) HW3 due
Wed 2/19 Midterm 1 Review L09, L09-ann Practice Midterm 1 solutions distributed in class
Mon 2/24 MIDTERM 1
Wed 2/26 Turing machines Sipser 3.1, 3.3, L10, L10-ann TM simulator, A real TM
Mon 3/2 TM variants, Church-Turing Thesis Sipser 3.1-3.2, L11, L11-ann HW4 out
Wed 3/4 TM variants, Church-Turing Thesis (cont'd) Sipser 3.1-3.2, L12, L12-ann Mid-semester feedback
Mon 3/9 NO CLASS — Spring Break
Wed 3/11 NO CLASS — Spring Break
Mon 3/16 Decidable languages Sipser 4.1, L13, L13-ann HW5 out
Wed 3/18 Diagonalization Sipser 4.2, L14, L14-ann HW4 due
Mon 3/23 Undecidable and unrecognizable languages, reductions Sipser 4.2, 5.1, L15, L15-ann HW6 out
Wed 3/25 Mapping reductions Sipser 5.3, L16, L16-ann HW5 due
Mon 3/30 Midterm 2 Review L17, L17-ann HW6 due
Wed 4/1 MIDTERM 2 Midterm 2 distributed on Piazza (due 4/2)
Mon 4/6 Time complexity, P Sipser 7.1-7.2, L18, L18-ann HW7 out
Wed 4/8 Nondeterministic time, NP Sipser 7.3-7.4, L19, L19-ann
Mon 4/13 More on NP Sipser 7.3-7.4, L20, L20-ann HW7 due; HW8 out
Wed 4/15 Cook-Levin Theorem, NP-complete problems Sipser 7.4-7.5, L21, L21-ann
Mon 4/20 NO CLASS — Patriots' Day HW8 due (Tue); HW9 out
Wed 4/22 Space complexity, Savitch's Theorem Sipser 8.1-8.2, L22, L22-ann
Mon 4/27 PSPACE-completeness, TQBF, time and space hierarchy theorems Sipser 8.3, 9.1, L23, L23-ann HW9 due
Wed 4/29 Course Wrap-Up and Final Review L24, L24-ann
Tue 5/5-Thu 5/7 Final Exam

Texts and References

Required Textbook

Michael Sipser, Introduction to the Theory of Computation, 3rd Edition. ISBN-13: 978-1133187790.
See here for a list of errata.

Reading the textbook before class and reviewing it after class are important for solidifying your understanding of the course material. However, I do not want the exhorbitant price of the book to pose a barrier to your learning. Using an older edition of the text is fine (though beware that section numbers may be different). If the cost of the textbook still presents a burden for you, let me know and I can loan you a copy or recommend another solution.

Other Resources

Proof Techniques:
Richard Hammack, Book of Proof. Available online here.

Automata and Computability Theory:
Dexter Kozen, Automata and Computability.

Complexity Theory:
Sanjeev Arora and Boaz Barak, Computational Complexity: A Modern Approach.
Cristopher Moore and Stephan Mertens, The Nature of Computation.


Your grade in the course will be determined by homework assignments, three in-class exams, and class participation.
The following letter grades are guaranteed if you earn the corresponding percentages: A ≥93%, A- ≥90%, B+ ≥87%, B ≥83%, B- ≥80%, C+ ≥75%, C ≥70%. However, to correct for the possibility of assignments and exams being more difficult than anticipated, letter grades may be (significantly) increased above these guarantees based on the overall performance of the class.

Homework (30%)

There will be weekly homework assignments to be submitted on Gradescope every Monday at 2PM. No late homework will be accepted. To accomodate extenuating circumstances, your two (edit 3/17) lowest homework grades will be dropped.

You are allowed, and indeed encouraged, to collaborate with other students on solving the homework problems. However, you must write the solutions independently in your own words. Details of the collaboration policy may be found here: Collaboration and Honesty Policy

Some homework assigments may include optional "bonus" problems. Solving these problems will not directly contribute to your homework grade but may improve the letter grade you receive in the course if the final percentage we calculate is on the borderline between two letter grades. Solving bonus problems is also a good way to impress your instructor if you are seeking a recommendation letter, research opportunities, or a grading position. Collaboration is NOT allowed on bonus problems.

You may want to use LaTeX to typeset your homework solutions. LaTeX is the standard document preparation system used in the mathematical sciences. Using LaTeX makes it easier for you to revise and edit your solutions and for us to read them, so you will never lose points for illegibility.

My preferred LaTeX editors are TexShop for Mac and TexStudio for Windows. If you would like to give LaTeX a try on the web without installing anything on your computer, Overleaf is a good option.

Not so short intro to LaTeX. A LaTeX tutorial.

Homework template files: tex, cls, jpg, pdf.

Midterm 1 (15%), Midterm 2 (15%), Final Exam (30%)

There will be two 70-minute in-class midterm exams scheduled for Monday, Feb. 24 and Wednesday, Apr. 1. These dates are confirmed and are not subject to change. Each midterm will cover roughly one-third of the course content. A comprehensive final exam will be held during the normal two-hour exam slot. Please wait until the official University final exam schedule is finalized before making your end-of-semester travel plans.

You may bring one double-sided 8.5" x 11" sheet of notes to each midterm exam and two such sheets to the final exam. Note sheets may be either handwritten or typeset. You may not use any other aids during the exam, including but not limited to books, lecture notes, calculators, phones, or laptops.

Class Participation (10%)

Your active participation in class and in discussion sections is an essential part of your learning. Your participation grade will be determined by your engagement with the Top Hat classroom response system. It will also be possible to increase this score by thoughtfully asking and answering questions in lectures, in discussions, on Piazza, or during office hours.

Course Policies

Academic Conduct

All Boston University students are expected to maintain high standards of academic honesty and integrity. It is your responsibility to be familiar with the Academic Conduct Code, which describes the ethical standards to which BU students are expected to adhere and students’ rights and responsibilities as members of BU’s learning community. All instances of cheating, plagiarism, and other forms of academic misconduct will be addressed in accordance with this policy. Penalties for academic misconduct can range from failing an assignment or course to suspension or expulsion from the university.


Attendance Policy

Students are expected to attend each class session unless they have a valid reason for being absent. If you must miss class due to illness or another reason, please notify the instructor as soon as possible, ideally before the absence.


Absence Due to Religious Observance

If you must miss class due to religious observance, you will not be penalized for that absence and you will receive a reasonable opportunity to make up any work or examinations that you may miss. Please notify the instructor of absences for religious observance as soon as possible, ideally before the absence.



In the event of the death of an immediate family member, you should notify your advisor, who will help you coordinate your leave. You will be automatically granted five weekdays of leave, and if necessary, you advisor will help you to petition the Dean for additional leave time. You may also request a leave of absence due to bereavement. Please contact your advisor, who will help you with the process.


Disability Services

Students with documented disabilities, including learning disabilities, may be entitled to accommodations intended to ensure that they have integrated and equal access to the academic, social, cultural, and recreational programs the university offers. Accommodations may include, but are not limited to, additional time on tests, staggered homework assignments, note-taking assistance. If you believe you should receive accommodations, please contact the Office of Disability Services to discuss your situation. This office can give you a letter that you can share with instructors of your classes outlining the accommodations you should receive. The letter will not contain any information about the reason for the accommodations.

If you already have a letter of accommodation, you are encouraged to share it with your instructor as soon as possible.

Disability & Access Services
25 Buick Street, Suite 300

Grade Grievances

If you feel that you have received an arbitrary grade in a course, you should attempt to meet with the grader before filing a formal appeal. If the student and the instructor are unable to arrive at a mutually agreeable solution, the student may file a formal appeal with the chair. This process must begin within six weeks of the grade posting. To understand how an “arbitrary grade” is defined, please explore the following link.


Incomplete Grades

An incomplete grade (I) is used only when the student has conferred with the instructor prior to the submission of grades and offered acceptable reasons for the incomplete work. If you wish to take an incomplete in this class, please contact the instructor as soon as possible but certainly before the submission of final grades. To receive an incomplete, you and your instructor must both sign an “Incomplete Grade Report” specifying the terms under which you will complete the class.


Student Health Services

Offers an array of health services to students, including wellness education and mental health services (behavioral medicine).


Medical Leave of Absence

If you must take a leave of absence for medical reasons and are seeking to re-enroll, documentation must be provided to Student Health Services so that you may re-enroll. To take a medical leave, please talk with SHS and your advisor, so that they may assist you in taking the best course of action for a successful return.



The International Students & Scholars Office is committed to helping international students integrate into the Boston University community, as well as answering and questions and facilitating any inquiries about documentation and visas.