CS70 ARCHIVED ANNOUNCEMENTS

• November 10: Prof. Sinclair's office hours next week (11/12 and 11/13) are canceled. See below for additional TA office hours this week.


• November 10: Sample Midterm 2 is posted below. This midterm will be the basis of the Review Session in next Tuesday's lecture (11/13). You are strongly advised to work through as much of the midterm as you can before the review session.


• November 8: Solutions to HW9 are posted below. (A revised version will be posted later to include comments after the HW is graded.)


• November 7: There is a typo in Q2 of HW9. In Q2(b) and (c), the definition of the event B should be "the family has at MOST one girl." (The definition of event A is correct as stated.) [The original question still makes sense, but the solution with this modified definition of B is more interesting.] If you have already done this problem with the old definition of B, it should not take you more than a few minutes to re-do it with the new definition. Apologies for the inconvenience.


• November 7: Recall that the second midterm will be held next Thursday, 11/15, 7-9pm in 10 Evans. The midterm will be closed book with no electronic devices, but you may bring in a one-sided, standard size cheat-sheet. The topics to be covered include everything from polynomials/secret sharing through basic probability (Notes 6 through 12 inclusive, HWs 5 through 9 inclusive). Here are some changes to next week's schedule to accommodate the midterm:
  
  - Next Tuesday's lecture (11/13) will be a review session. The TAs will go over a sample midterm that will be posted in advance.
  - Next Thursday's lecture (11/15) is canceled because of the midterm that evening.
  - There will be no sections next week. Instead, there will be additional office hours on Wednesday afternoon as follows: Assane 1-2pm, Luqman 3-4pm, Vahab 4-5pm. (These are in addition to regular office hours.)
  - There will be no HW due next week.
  


• November 6: HW8 solutions are posted below. The statistics were as follows: Mean 35.1 (out of 47), Median 36, Stdev 9.7, Min 9, Max 47.


• November 5: There are a couple of typos in Note 11, page 5, section "Balls and bins". Starting with line 3:
  
  1) The set A should be an intersection from i=1 to m (not n), as the number of balls is m.
  2) Pr[Ai] should be 1-1/n (not 1/n).
  3) In the final formula, the Pr[A_i] should end at Pr[A_m], not at Pr[A_n].
  


• November 5: There is a typo in Q5(b) of HW9. In the displayed equation, "Pr[E|W_k]" should be "Pr[R|W_k]". Apologies for the confusion.


• November 1: HW9 is posted below; it is due next Thursday, Nov 8. This is the last HW before the second midterm (which is on Thursday Nov. 15).


• October 30: Solutions for HW7 are posted below. The statistics are as follows: Mean 43.0 (out of 55), Median 46, Max 55, Min 11, Stdev 11.4.


• October 25: HW8 is posted below. It is due next Thursday, November 1. The topic is Probability (lecture notes posted below). It is essential that you understand these basic probability concepts before we go on to more complex stuff, so please think about this homework carefully. As always, help is available at office hours.


• October 23: HW6 solutions are posted below. The statistics are as follows: Mean 32.4 (out of 45), Median 34, Max 45, Min 7, Stdev 10.1.


• October 18: HW5 solutions are posted below. The statistics are as follows: Mean 38.1 (out of 44), Median 40, Max 44, Min 12, Stdev 5.5.


• October 18: HW7 is posted below; it is due next Thursday, October 25. This HW is slightly longer than HW6, mainly because we shifted one problem (Q1) from HW6 to HW7. As always, start early! You already have the information needed for all of the HW except for~Q5.


• October 16: Important announcement: Q4 on HW6 requires material that I did not get to in class today; I will cover this at the beginning of Thursday's lecture. For this reason, this problem is withdrawn from HW6; it will instead appear as Q1 on HW7. So if you have figured it out you have not wasted your time; but please do not turn it in this week. Apologies for the inconvenience.


• October 16: A reminder that the box of uncollected homeworks outside Vahab's office is now being cleaned out. If you want to retrieve an old homework then you need to go to one of Vahab's office hours. Uncollected homeworks starting from HW5 will be placed in the box.


• October 16: Here are a few typos in homeworks/notes/solutions that have been brought to my attention:
  
  - Midterm solutions, Q1(b): the only two correct approaches are (i) and (iii) [not (i) and (ii) as originally stated]. This is a typo; the problem was correctly graded.
  - HW6, Q2(b): The NOTE is not correct, since when d=0 you need one (not zero!) paths to cover the graph - though of course in that case the path is a cycle. This does not affect the statement of the problem, which is correct.
  - Note 8, p5, last line but one before "Hamiltonian paths and cycles". The number 2^{n}-1 should be 2^{n-1} (i.e., n-1 in the exponent).
  
  These changes have now been made in the posted versions. Apologies for any confusion caused by these.


• October 11: Lecture notes for Graphs (today's lecture and the next lecture) are posted below. Homework 6 is also posted below; it is due next Thursday. As of today's lecture you have enough information to tackle Q1 and Q2; Q3 and Q4 will be covered in the next lecture (or you can read ahead in the notes). Please start early!


• October 10: The midterm has been graded, and will be returned in sections today. Here are the statistics: median: 53 (out of 60), mean: 51.7, stdev: 6.7, min: 25, max:60. These are very high scores. The midterm was a good test of basic understanding of the material, and I am glad to see that the majority of the class seems to have mastered this. By the same token, those students who scored poorly clearly have major holes in their understanding. Everybody (even those who scored 60 out of 60) should carefully go over the sample solutions posted below. If you scored less than 40 on the midterm, please come and see me at one of my office hours early next week.


• October 8: Important announcement: The homework return box is now full of uncollected homeworks. As a result, we will be emptying it one week from today, on Monday October 15th. Any homeworks uncollected by that date can be collected only by arrangement with your TA. Please collect your homeworks now!


• October 7: There is a small typo in Lecture Note 6 ("Polynomials"). On page 3, line 2 of the section "Uniqueness", "property 1" should read "property 2".


• October 7: Notes for error-correcting codes are posted below.


• October 4: HW5 is posted below; it is due next Thursday (October 11). The topic is polynomials and secret sharing. Please start early!


• October 3: There is a revised version of the HW4 solutions posted below (including comments on typical mistakes). Statistics for HW4: Mean 46.9 (out of 56), Median 48, SD 8.34, Max 56, Min 15.


• October 2: HW4 is now graded; you can pick up your solutions from your section TA at one of the special office hours on Wednesday (10/3). Uncollected solutions will be place in the usual box.


• October 2: Recall that there are no homework and no sections this week. Instead, there will be addtional office hours on Wednesday (10/3) as follows: Assane 1-2pm in 307 Cory; Luqman 3-4pm in 592 Soda; Vahab 4-5pm in 405 Soda.


• September 29: Sample Midterm 1 is posted below (under "Exams"). You are strongly encouraged to work through this before the Review Session during Tuesday's lecture, when it will be discussed in detail. In addition, the solutions to HW4 are posted below so that you can view them before the midterm. [Note that they may be slightly revised after the HW is graded, to take into account feedback from the readers.] Lecture notes on Polynomials are also posted below; however, this topic is not included on the midterm. Finally, a revised version of the notes from Week 5 Sections is posted below.


• September 27: Recall that the first midterm will be held next Wednesday, 10/3, 6-8pm in 10 Evans. The midterm will be closed book with no electronic devices, but you may bring in a one-sided, standard size cheat-sheet. The topics to be covered include everything up to but not including polynomials (i.e., everything covered on HWs 1 through 4). Here are some changes to next week's schedule to accommodate the midterm:
  
  - Next Tuesday's lecture will be a review session. The TAs will go over a sample midterm that will be posted in advance.
  - There will be no sections next week. Instead, there will be office hours on Wednesday afternoon (times/rooms to be announced).
  - There will be no HW due next week. HW5 will go out next Thursday and will be due the following week.


• September 27: Solutions for HW3 are posted below. The statistics are as follows: mean 28.2 (out of 33), median 29, SD 3.1, max 33, min 14.


• September 25: Another minor typo in HW4. In Q3, the symbol &equiv should be = (in all four places). (The two symbols are equivalent in this context. In this course, we are just using the symbol =)


• September 25: There is minor typo in Q2 of HW4. In the "i.e." remark in parentheses involving the summation, ">" should be replaced by "<".


• September 20: HW4 is posted below. It is due next Thursday, 9/27. Please start early!


• September 19: HW2 solutions are posted below; everybody is encouraged to read them carefully. Here are the statistics: Mean 31 (out of 39), Median 32, SD 6.4, Max 39, Min 3.


• September 18: There is a small omission from Q3(a) in HW3. In the definition of the ordering in this part, we define (a,b) <1 (c,d) if a/b < c/d, or if a/b = c/d and a < c, *** or if a/b = c/d and a = c and b < d ***. (The part between *** ... *** is added.) This ensures that all pairs of elements are comparable. Apologies for any confusion.


• September 18: The location for both of Vahab's office hours is changed to 751 Soda Hall, effective this week.


• September 17: Important changes in office hours and sections:
  1. Vahab's Section (103, 4-5pm) will move to 405 Soda starting this week.
  2. There is no change in the rooms for any other sections.
  3. Vahab's Monday office hour is moved to Wed 5-6pm, starting this week. A new room for both of Vahab's office hours will be announced shortly.


• September 17: Here are the statistics for HW1 (for future homeworks we will aim to post these earlier). Mean 38.6 (out of 45), median 41, SD 5.6, max 45, min 16.


• September 13: Please note that the room for Assane's office hours has been changed to 212 Cory, effective next week (September 20). The times of the office hours remain the same.


• September 13: Homework 3 is posted below; it is due next Thursday, September 20. As usual, you are advised to start early!


• September 13: Homeworks that were not collected in section can be picked up from a box outside Vahab's office (594 Soda) from this afternoon onwards. Please pick up your homeworks promptly.


• September 13: Handouts from sections are posted below (under DISCUSSION SECTIONS). Also, the next lecture note (Note 4), covering the last part of today's lecture and the next lecture, is posted below.


• September 12: As promised in class yesterday, here is the corrected url for further reading on the Four Color Theorem, as quoted in Note 3: www.math.gatech.edu/~thomas/FC/fourcolor.html (The very slightly revised version of the Note posted below included this correction.)


• September 12: HW1 solutions are posted below. You are strongly encouraged to work through the solutions even if you got maximum points on the HW.


• September 11: There will likely be some room changes for sections next week. These will be announced in due course. For this week, all sections will be in their original rooms.


• September 7: There is a typo in Q1(a) of HW2. The problem should read "for all n > 1" instead of "for all n >= 1". The version posted below contains this correction.


• September 6: Homework 2 is posted below; it is due next Thursday, 6/13. This homework covers induction, and is a bit longer than HW1. Please start early! Today's lecture covered all that you need to know for this homework; the notes are posted below.


• September 6: Here is a correction of the proof at the end of today's lecture. By convention 1 is NOT prime, so the theorem holds only for n >= 2. (The only possible factorization of 1 is 1x1, which is not a product of primes.) The induction proof remains valid, starting with 2 as the base case. The correct version is in the notes. Apologies for the confusion.


• September 5: Homework 1 is due TOMORROW (Thursday 9/6) at 5pm. Please carefully follow the instructions for submitting your homework; failure to follow the instructions may result in zero or reduced credit!


• September 5: The midterm dates are confirmed as follows:
  First Midterm: Wednesday 10/3, 6-8pm, in 10 Evans
  Second Midterm: Thursday 11/15, 7-9pm, in 10 Evans
  Anybody who has a legitimate conflict with one of these dates should contact me as soon as possible.


• August 30: Homework 1 is posted below; it is due next Thursday, September 6. Lecture Note 2 is also posted below.


• August 28: In response to many questions at today's lecture, here is the policy regarding prerequisites. If you have not taken the CS61A prerequisite, but you are EITHER taking it this semester simultaneously with CS70 OR have equivalent programming experience from elsewhere (e.g., CS61B or equivalent) then this prerequisite is waived. However, you should be aware that basic programming skills, as well as some knowledge of recursion (both of which are covered in CS61A), will be assumed in CS70. The other prerequisites (Math1A and Math1B) are NOT waived.


• August 28: The first set of lecture notes is posted below, along with a pointer to the relevant sections in the book. There are NO DISCUSSION SECTIONS this week; discussion sections start next week (Wednesday 9/5). The FIRST HOMEWORK will be posted this Thursday 8/30 and will be due the following Thursday, 9/6.


• August 27: Welcome to CS70! Please read this web page carefully; it contains the answers to most of the administrative questions you are likely to ask.