# CMSC 250

## Introduction to Discrete Structures

### Important Announcements

May 16
• SOLUTIONS to HW 12 and 13 posted
May 15
• SOLUTIONS to Practice Final posted (click on Exams)
• Charles Lin will hold additional office hours Wednesday 11 AM to 1 PM. He will not hold office hours on Thursday or Friday.
• Brian will hold office hours on Friday to cover Charles (around 2:30-4:30).
• TA office hours end on Tuesday.
May 14
• Midterm 2 and Midterm 2 solutions posted
May 13
• Solutions to Midterm 1 posted
May 12
• Notes on 5-coloring of planar graphs available. Click on Notes link.
May 10
• HW 13. Note: the root of the tree can have degree up to k. The rest of the nodes (having a parent) can have up to k + 1.
• Sample Final posted. Click on Exams. (Correction: back to being 12 colorable)
May 9
• HW 13 posted (due NEXT MONDAY)
May 7
• HW 12 posted.
• HW 11 solutions posted
Apr 22
• HW 10 posted.
• HW 8 and 9 solutions posted.
Apr 11
Apr 3
• HW 8 now posted.
• Quiz on Monday as usual.
• Exam will be returned on Wednesday.
• April 13 (Friday). Last day to drop course with W.
Apr 3
• REVIEW SESSION TODAY! 5-7 PM at BPS 1243 (we believe this is correct...this room seats about 100, and should be near BPS 1240, a very large lecture hall). Larry will answer questions.
• Practice Homework on NIM (Homework 7.5) and solutions located here. May wish to look over before the exam.
Apr 2
• HW 7 solution posted

Apr 1

• REVIEW SESSION
• Tuesday, 5-7 PM (by Larry). BPS 1243 (we think). (If not, check BPS 1240).
• Wednesday, 6-8 PM (by Bill). SKN 0200.
• TAs will also review in lab.
• HW 7 is due MONDAY, not WEDNESDAY!
• HW 6 solutions posted. HW 7 should be posted Monday evening.
• Sample Midterm 2 solutions posted. See Exam link.
Mar 28
• HW 7 posted. (Note: Problem 5 requires additional base cases---you must decide which ones based on proof).
Mar 28
• Midterm 2 will be April 5, from 6-7:30 PM. Room to be announced.
• HW 7 to be posted soon. HW 6 solution to be posted soon.
Mar 11
• Corrections made to the two handouts Charles made on March 5 and March 7. Many errors. Should be mostly fixed. See Notes links to get new copies.
• Charles will lecture for CMSC 250 on Monday in the usual room and usual time.
Mar 9
• Midterm 1 posted. See Exam link.
• Regrade requests accepted until next Wednesday in lecture or lab. You must fill out a sheet. We will return regraded exams after Spring Break. We reserve the right to regrade the entire exam (your grade may decrease). Alterations to the exam is considered an act of academic dishonesty, and may result in charges brought to Office of Judicial Programs and an XF for those found responsible for altering official university documents.
• Office hours for Charles not held today (Friday). Charles will hold an additional hour on Tuesday from 3:30-4:30.
• HW 5 posting corrected (the links were incorrect)
• HW 4 solutions posted (send email to clin@umd5.umd.edu if you find errors)
• Charles had handouts on Monday, March 5 and Wednesday, March 7. Click on Notes links to find them.
Mar 7
• New HW5 posted.
• HW4 solution posted soon.
Mar 2
• New HW4 posted.
• Quiz next Monday, as usual (on material from this week).
Feb 28
• Due to various typos and problems with HW 4, a new version will be handed out during the exam or in class Friday. That version will be posted soon.
• Link to circuits HW fixed.
• HW 3 solutions posted.

Feb 27

• The "circuits" homework and solution can be found here. These were handed out in discussion on Monday. They are not collected, and are there for test preparation.
• Sample Midterm 1 solutions posted. See Exams link above.
• HW 3 solutions will be posted by tomorrow, shortly after discussion section.
Feb 26
• Correction! Brian's sections should be in Skinner. Charles's sections in Shoemaker. Skinner can seat at last 100 more than Shoemaker. The 0101 section for Brian should be in Shoemaker too.
• Correction! Problem 7 should not have the square brackets. The negation only applies to the first universal quantifier.
• Problem 2 should read "Every animal eats something".
Feb 25
• Q&A session: Monday, 5:30-7:30 JMP 3105 (should seat at least 40).
• Q&A session: Tuesday, 5-6:30 CLB 0102 (should seat many!)
• TAs will also answer exam related questions in lab on Wednesday.
• Material on exam will be up to material covered in class on last Friday (up to adders). The primary focus will be translations, proofs, understanding predicates (domains, etc). You are also responsible for some circuit stuff, especially Wednesday's material, but even Friday as well. Reviewing your old homeworks may be useful preparing for the exam.
Feb 24
• Quiz Monday on circuits.
• Want to print Postscript files on PCs? Here is a link that some students have used: Ghosview 6.50 link. Note that you will need to download Ghostscript 6.50 AND gsv36w32.exe (also note that the instructors have not tried this out--this is however, posted at the University of Wisconsin's computer science site). Go down to the section that says "Windows 95, 98 or NT". You should only need to download the two links: gs650w32.exe and gsv36w32.exe. I assume you extract the first one (which is Ghostview), followed by the second (GSView). Again, I've never done this, but for those who have a laser printer at home/dorm, or just want to view, you can.
• Exam information available in the Exam link above.
• Sample Midterm available in the Exam link.
• Sample Midterm solution available by Tuesday.
• Proof Rules/Equivalence Rules are also in the Exam link. You may use this as part of your cheat sheet.
• Both sample midterm and proof rule sheet should be (soon) available outside the TA office in the hanging folder. If not, send email to: clin@umd5.umd.edu.
• HW 2 solution to be posted soon.
• HW 3 solution will be handed out in discussion on Wednesday.
Feb 19
• Report any problems with links to: clin@umd5.umd.edu (Charles)
Feb 14
• Ah. Valentine's Day.
• Homework 1 solution posted (click Homework link above).
• HW 2 posted.
Feb 9
• Want to practice proofs? Do HW 1.5 (which is not to be collected). It's here.
• HW 1 posted (click on Homework above). Here's how to print homeworks.
• Quiz Monday!
Feb 5
• Webpage is up! (Sorta)
• Quiz today!

Problems? Send email to Charles or webmaster Bill
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