This is the home page for CMPSCI 250. CMPSCI 250 is the undergraduate core course in discrete mathematics and will deal with logic, elementary number theory, proof by induction, recursion on trees, search algorithms, finite state machines, and a bit of computability.

**Instructor Contact Info:**
David Mix Barrington, 210 CMPSCI
building, 545-4329, office hours Tuesday 11-12, Wednesday 2:30-3:30,
Thursday 3-4, Friday 3:30-4:30.
I generally answer my email fairly
reliably.

**TA Contact Info:** Cibele Friere
(cibelemf@cs.umass.edu), office hours Thursday noon-1,
Arti Ramesh
(artir@cs.umass.edu), office hours
Tuesday 2-3, and
Samamon Khemmarat
(khemmarat@ecs.umass.edu), office hours Monday 2-3.
TA office hours are in LGRT 220.

The course is primarily intended for undergraduates in computer science and related majors such as mathematics or computer engineering. CMPSCI 187 (programming with data structures) and MATH 132 (Calculus II) are corequisites and in fact most students in the course have already taken both.

The course meets for three lecture meetings a week, Monday, Wednesday, and Friday, at 11:15-12:05, in Hasbrouck room 134.

There is one discussion meeting per week for each of the two sections, with Section D01 meeting Friday 12:20-1:10 p.m. and Section D02 meeting Friday 2:30-3:20 p.m., both in room 142 of the Computer Science building. Most discussions will have a written assignment which you will carry out in groups, chosen randomly at the beginning of each discussion. Discussion attendance is required, so that missing a discussion will incur a grade penalty. The TA's and I will cover the sections in various combinations, so they should be as interchangeable as we can make them. (D02 is currently more crowded -- anyone who can switch to D01 is encouraged to do so.)

The textbook is several chapters of my draft version of
*Discrete Mathematics: A Foundation for Computer Science*. Photocopies
of this will be available before the start of term,
for $53 (two volumes), at
Collective Copies in downtown
Amherst. Ask for course packet #21.
(Dave gets none of this money -- it is the
copying cost only.) The Spring 2012 version will have only a few minor edits
from the Spring 2011 version, mostly correcting the errors noted on the Spring
2011 web site. The Fall 2010 version has a few more changes including four
missing pages (which I can email you on request).

- Course Requirements and Grading
- Learning Goals for the Course
- Homework Assignment Directory (with #9)
- Lecture Slides (through #39)
- Exam Directory (with midterm #2 and solution)
- Questions and Answers on Homework (with some on #1)
- Syllabus
- Errata in the (Spring 2012) Textbook (with some on Chapter 2)

**Announcements (4 June 2012):**

- (4 Jun) Sorry for the delay -- I have finally posted the final exam text and solution. Thanks again for an enjoyable course.
- (12 May) I have finally completed grading the final exams
and have posted grades to SPIRE. If you got a grade
*below C*, I have emailed you at the address SPIRE has for you -- otherwise you got a C or better.The final exam grades (including the extra points for finding mistakes during the semsester) ranged from two 124's at the top to a 39, two 36's, and a 12 at the bottom. The median was an 80. I set the scale at A = 105, B = 86, C = 68, D = 49, F = 30. In all 21 exams were below the C range.

Overall grades for the 84 people who took the final were ten A's (four of them unofficial A+'s, for which I will file course citations with the CMPSCI main office), 12 A-'s, 9 B+'s, 13 B's, 14 B-'s, 11 C+'s, 4 C's, 8 C-'s, 1 D, and 2 F's.

I have to be out of town through Wednesday, so I will probably post the exam and solutions on Thursday. Thank you all for a very enjoyable and mostly successful course.

- (30 Apr) Office hours for this week are given on my main page. I have graded HW#7 and HW#8 and can give them back during those office hours. I plan to schedule a review session for the final, sometime on Monday 7 May.
- (23 Apr) I've edited the notes from this
morning to fix the example on the next to last slide. Also, please note
an error in the text that is relevant if you attempt the second writing
assignment for Excursion 14.9. On page 14-53, the regular expression on the
last line should be "[λ + a + ba + aba]b
^{*}", rather than what it says now with the third term "ab". - (22 Apr) I will be away Thursday afternoon 26 April -- I will hold office hours 10:30-11:30 instead of 3:00-4:00.
- (20 Apr) I've posted the last HW assignment. due a week from Tuesday. The first few problems are on material we've seen already. There are 20 points of extra credit if you're ambitious.
- (14 Apr) I've posted the HW#8 assignment, due on Friday. There are 15 points of extra credit, not as outlandish as the chess problem on HW#7, which gives you a chance to make up for earlier low HW grades if you can.
- (11 Apr) I have posted the second midterm and its solution.
- (11 Apr) I must cancel my office hours tomorrow, sorry.
- (9 Apr) I have now graded the exams and will give them back in lecture today.
Top was 106 (two of them along with two 105's) and there were four below 40. The
median was 78.
The scale is A = 93, C = 65 -- here are the ranges for individual grades and the number
getting each grade:
- A+ (unofficial) 96-106 (12)
- A 91-95 (8)
- A- 86-90 (6)
- B+ 82-85 (6)
- B 77-81 (15)
- B- 72-76 (9)
- C+ 68-71 (5)
- C 63-67 (9)
- C- 58-62 (8)
- D+ 54-57 (3)
- D 49-53 (2)
- F 0-46 (4)

- (3 Apr) The exam seemed to go smoothly -- I will shoot for getting the graded papers back to you by Monday. I also owe you a HW#7 assignment soon. The lecture notes for tomorrow are up. We are starting on the final third of the course, on regular languages and finite-state machines.
- (1 Apr) The notes for tomorrow's lecture are up. As I've said in lecture, Tuesday night's exam (in Morrill 2 room 131 from 7-9 p.m.) will be similar in material and format to the Spring 2011 and Fall 2010 second midterms. There will be very little or nothing on adversary search, but the rest of Chapter 9 (the sections on the syllabus) are fair game. Good things to study are the solutions to the prior exams, the homeworks (HW#6 solutions were emailed to you earlier today) and the discussions. There won't be questions specifically aimed at material from the first third of the course, but the general proof techniques used there are important, particularly the Rule of Generalization.
- (17 Mar) The HW#6 assignment is up, due the Friday after break. The second midterm is the evening of the second Tuesday after break, which is 3 April.
- (17 Mar) The scale for HW#1 is indeed A = 54, C = 36, and
the scales for HW#2 and HW#3 are indeed A = 48, C = 30. Graded
HW#4's will be returned the Monday after break and I hope that
graded
HW#5's will follow soon. I also owe you solutions for HW#5 which I
hope
I will have soon.
Some more stats on the first midterm: The high was 99, the median 61, and the low 25. There were 4 A+'s (88-99), 3 A's (83-87), 7 A-'s (78-82), 8 B+'s (73-77), 10 B's (68-72), 9 B-'s (63-67), 14 C+'s (58-62), 12 C's (53-57), 7 C-'s (48-52), 7 D+'s (43-47), 6 D's (38-42), and 5 F's (25-37).

- (10 Mar) The HW#5 assignment is up.
- (9 Mar) I've just posted the next lecture notes -- sorry I've been slow with these. I owe you the scale for the first three homeworks, and some stats on the midterm -- I'll probably get to these tonight (Friday night). The HW#1 scale will probably be A = 54, C = 36, the HW#2 scale will probably be A = 48, C = 30, and the HW#3 scale might be either of those or somewhere in between. I should also have the HW#5 assignment up by Friday night.
- (7 Mar) I've posted solutions for the first midterm. The scale was A = 85, B = 70, C = 55, D = 40. The high was 99 and the low was 26 -- the mean was about 60. I will have more detailed stats here tomorrow. Some of you may want to consider a late drop of the course before the March 13 deadline (next Tuesday) -- I can talk to anyone individually about that in office hours or by appointment.
- (6 Mar) I've just put up the notes for tomorrow's lecture. I will have graded midterms and HW#3's available for the lecture -- I will try to get there before class to distribute as many as I can and then do the rest afterward. (Now to finish the last 28 midterms...) The current target for posting solutions is tomorrow night.
- (4 Mar) I've posted the midterm questions and tomorrow's lecture. I've done about half the grading -- the exams are disappointing but I think I can come up with a reasonable scale. I am still shooting for returning graded exams on Wednesday -- I will also post solutions when I get a chance.
- (2 Mar) The HW#4 assignment is up. Actually it has been up since early this afternoon -- thanks to the student who noticed that I hadn't updated this page.
- (26 Feb) I have emailed out solutions to HW#3, and I have just posted lecture notes for tomorrow. Tomorrow's lecture is fair game for Tuesday night's exam.
- (24 Feb) Tomorrow's lecture notes are finally up -- I will try to do better about getting these ready in advance.
- (23 Feb) Remember that there is no discussion class tomorrow. I have had to schedule another meeting during my regular office hour tomorrow (3:30-4:30), so I will have office hours 2:30-3:30 instead.
- (23 Feb) The exam next Tuesday evening is in Morrill 2, room 131, from 7-9 p.m. -- if you have a time conflict I should have heard from you already, but we may still be able to work something out.
- (21 Feb) Tomorrow's slides are now posted.
- (21 Feb) I have to go give the CMPSCI 401 midterm now, and the lecture notes for tomorrow are not quite finished. I will post them later tonight.
- (15 Feb) The HW#3 assignment is now up. I will email out HW#2 solutions when I get them, probably sometime tomorrow.
- (15 Feb) The HW#3 assignment, due a week from Friday, will be posted sometime tonight.
- (15 Feb) As I mentioned is class today, prime numbers and factoring
are relevant to the practice of computing, as reported in the
*New York Times*. - (13 Feb) Graded HW#1's were returned in class -- I will bring the remaining papers in on Wednesday. If you have an issue with the grading, the first step is to email Cibele, the lead TA, or come to her office hours. She can track down who graded the problem and whether a change is warranted. We can't be all that flexible in changing grades because we need to be consistent across everyone, but we can correct clear errors.
- (13 Feb) If you are using a green textbook from Fall 2010, I hope you will soon notice that it is missing section 2.11, the material for next Wednesday's lecture. If you email me, I will email you back a PDF of the missing pages.
- (9 Feb) Arti and Samamon have changed their office hours for the rest of the term -- see above.
- (5 Feb) Well, that was a disappointing result, but congrats to the Giants. It's not often in football that your best strategy is to allow your opponent to score a touchdown...
- (4 Feb) A student has found a mistake in
HW#2, which I have now corrected. If this had happened nearer the deadline, I would have emailed everyone, but earlier in the process I will count on your looking at the assignment web page. - (31 Jan) I've posted the first questions and answers on HW#1. I'll add to this page as I get more questions. Note that I won't always announce here when I've started a page, and I sometimes forget to update the text on the links above. But my naming conventions for pages on this site are pretty obvious, so you can always look to see whether a given page exists. Extra exam points are sometimes available for reporting broken links or other errors.
- (28 Jan) I've started the errata page for the yellow textbook. Remember that if you have a blue or green textbook, you will need to look at the prior errata pages.
- (27 Jan) I cannot make my office hours today because of a suddenly-called faculty meeting. I will be reading email through the weekend.
- (24 Jan) I have posted the first homework assignment, due on paper in class a week from Friday.
- (23 Jan) The book I mentioned in class, which I think every computer
science or math major should read, is
*Godel, Escher, Bach*by Douglas Hofstadter . A student points out that some people on reddit have organized a read through of this book, and they are only a week into it and still on the first chapter. (Link to reddit fixed later on 23 Jan.) - (23 Jan) I've corrected an error on the syllabus, so that it now gives the correct classroom for lectures. The good news is that the student who reported this error to me gets an extra point on the final exam. The bad news is that the error is reproduced in all the textbooks. (You might want to correct yours in pencil.)
- (23 Jan) The textbook is available at Collective Copies. It is course packet #21 and costs $53 for the two volumes.
- (18 Jan) I've given the originals for the textbook course packet to Collective Copies. They will likely have packets available by Monday (possibly sooner). I will put ordering and price information here when they are ready.
- (18 Jan) The slides for the first lecture are now up.
- (14 Jan) I've posted a list of learning goals for the course, originally compiled as a study guide for the Fall 2010 final.
- (14 Jan) This course is open on SPIRE, but restricted there
to certain majors (CMPSCI, Math, and ECE, for which it can serve as
a required course) and to those with
*both*CMPSCI 187 (or ECE 242) and MATH 132. Students who have taken one of those two courses and are enrolled in the other*may*be eligible to take CMPSCI 250 this term -- email me if you are interested. - (11 Jan) Welcome to the preliminary version of the web site for CMPSCI 250 for Spring 2012. I am setting up the bare bones of the web site today. This section of the CMPSCI 250 main page will be essentially a blog of course announcements. In most respects the course will run like the Spring 2011 version of CMPSCI 250.

Last modified 4 June 2012