CS 3100

Data Structures and Algorithms 2

Announcements, Fall 2025

Mark Floryan (mrf8t@virginia.edu)
Aaron Bloomfield (aaron@virginia.edu)
@github | ↑ |

Good Code

You can either hang out in the Android Loop or the HURD loop.

xkcd # 844

Lecture 13: Tuesday, October 7th

Office hours are listed on the Canvas landing page, and are:
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
- No OH Thursday (exam grading), nor Monday (fall break); some OH will be held next Tuesday (details TBA)
Midterm 1 (aka quizzes 1 & 2) is/are Thursday of next week (Oct 9th)
- Old quizzes are in Canvas’ Files
- Solutions to PS1 and PS2 are now in Canvas’ files
- Solutions to PS3 can be released today
- Solutions to PS4 will be released next Wednesday (most likely)
Assignments:
- PS5 will be out Thursday, due next week
- PA3 should be out early next week, due two weeks from this Friday
Course textbook link is on the Canvas landing page
Grading: PS0, PS1, and PS2 returned, as was PA1
- Gradescope will hold the grades, including any late penalties, as will Canvas’ gradebook
- HOWEVER, Canvas’ gradebook does not always sync immediately with Gradescope
Regrades:
- PSs and quizzes: once it is returned and announced, there is a 1 week window to submit a regrade through Gradescope
- PAs: because it is auto-graded, there will be a Piazza thread for each PA to work through grading concerns
Today we will start on greedy algorithms

Here to Help

"We TOLD you it was hard." "Yeah, but now that I'VE tried, we KNOW it's hard."

xkcd # 1831

Lecture 12: Thursday, October 2nd

Assignments:
- PS4 was due yesterday – how did it go?
- PA2 is due tomorrow (Friday, October 3rd); Gradescope submission is open
- No assignments due next week because of the midterm
Course textbook link is on the Canvas landing page
Office hours are listed on the Canvas landing page, and are:
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Grading: PS0, PS1, and PS2 returned, as was PA1
- Gradescope will hold the grades, including any late penalties, as will Canvas’ gradebook
- HOWEVER, Canvas’ gradebook does not always sync immediately with Gradescope
Regrades:
- PSs and quizzes: once it is returned and announced, there is a 1 week window to submit a regrade through Gradescope
- PAs: because it is auto-graded, there will be a Piazza thread for each PA to work through grading concerns
Midterm 1 (aka quizzes 1 & 2) is/are Thursday of next week (Oct 9th)
- Old quizzes are in Canvas’ Files
- Solutions to PS1 and PS2 are now in Canvas’ files
- Solutions to PS3 can be released today
- Solutions to PS4 will be released next Wednesday (most likely)
Today we will continue, and possibly finish, with divide & conquer

Coordinate Plane Closure

3D graphs that don't contact the plane in the closure area may proceed as scheduled, but be alert for possible collisions with 2D graph lines that reach the hole and unexpectedly enter 3D space.

xkcd # 2735

Lecture 11: Tuesday, September 30th

Assignments:
- PS4 is due tomorrow (Wednesday, October 1st)
- PA2, due this Friday (October 3rd), is out; Gradescope submission is open
- No assignments due next week because of the midterm
Course textbook link is on the Canvas landing page
Office hours are listed on the Canvas landing page, and are:
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Grading: most things are graded (PS0, PS1, PS2, PA1), but we are working to ensure that the extensions and late penalties are computed properly before returning them. Expect them all this week.
- Gradescope will hold the grades, as will Canvas’ gradebook
- HOWEVER, Canvas’ gradebook does not always sync immediately with Gradescope
Regrades:
- PSs and quizzes: once it is returned and announced, there is a 1 week window to submit a regrade through Gradescope
- PAs: because it is auto-graded, there will be a Piazza thread for each PA to work through grading concerns
Midterm 1 (aka quizzes 1 & 2) are Thursday of next week (Oct 9th)
- Old quizzes are in Canvas’ Files
- Solutions to PS1 and PS2 are now in Canvas’ files
- Solutions to PS3 can be released on Thursday
- Solutions to PS4 will not be released before the exam because they can be turned in up until the day before
Today we will continue with divide & conquer

Flow Charts

At 8 drinks, you switch the torrent from FreeBSD to Microsoft Bob. C'mon, it'll be fun!

xkcd # 518

Lecture 10: Thursday, September 25th

Assignments:
- PS4 will be out today
- PA2, due next Friday (Oct 3), is out; Gradescope submission is open
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Grading: most things are graded (PS0, PS1, PS2, PA1), but we are working to ensure that the extensions and late penalties are computed properly before returning them. Expect them all within a week.
Midterm 1 (aka quizzes 1 & 2) is the week after next, on Thursday
- Solutions to most/all problem sets will be made available
- PS4 solutions may not because of the late due date
Today we will continue with divide & conquer

Pillow Talk

xkcd # 69

Lecture 9: Tuesday, September 23rd

Assignments:
- PS3 is out, and due tomorrow (Wed, Sep 24)
- PS4 will be out on Thursday
  - Gradescope submissions open up 72 hours before the due date
- PA1 was due last week – how was it?
  - Note that acceptance tests are not the same as the grading tests!
  - You cannot use GenAI for the code you write (but can use it as a reference for, say, how to call a given function)
- PA2, due next Friday (Sep 29), is out
  - Gradescope will open in a day or two
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Today we will continue with divide & conquer

Linear Sort

The best case is O(n), and the worst case is that someone checks why.

xkcd # 3026

Lecture 8: Thursday, September 18th

Assignments:
- PS2 was due yesterday by 11:59 pm; how did it go?
- PS3 will be out later today
  - Gradescope submissions open up 72 hours before the due date
- PA1 is out, due tomorrow (Friday, September 19) by 11:59 pm
  - Note that acceptance tests are not the same as the grading tests!
  - You cannot use GenAI for the code you write (but can use it as a reference for, say, how to call a given function)
- PA2, due next-next Friday (Sep 29), will be out today or tomorrow, on divide & conquer
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Today we will start on divide & conquer

Google Maps

Apparently Google assumes you're traveling during the ferry's normal operating hours. We lost two hours circling that damn lake (to say nothing of the Straw Man).

xkcd # 461

Lecture 7: Tuesday, September 16th

Assignments:
- PS2 is due tomorrow (Wednesday, Sep 17th), by 11:59 pm
  - Gradescope submissions open up 72 hours before the due date
- PS3 will be out Thursday
- PA1 is out, due next Friday (Sep 19) by 11:59 pm
  - Gradescope will open up later this week
  - Note that acceptance tests are not the same as the grading tests!
  - You cannot use GenAI for the code you write (but can use it as a reference for, say, how to call a given function)
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Today we will finish graphs, and possibly start on divide & conquer

Dependencies

The prereqs for CPSC 357, the class on package management, are CPSC 432, CPSC 357, and glibc2.5 or later.

xkcd # 754

Lecture 6: Thursday, September 11th

PS1 is was due yesterday by 11:59 pm
- The extension system is linked to from the Canvas landing page
- Extensions can be submitted up to 3 days after the (original) due date
PS2 is out, due next Wednesday, Sep 17th, by 11:59 pm
- Gradescope submissions open up 72 hours before the due date
PA1 is out, due next Friday (Sep 19) by 11:59 pm
- Gradescope will open up later this week
- Note that acceptance tests are not the same as the grading tests!
- You cannot use GenAI for the code you write (but can use it as a reference for, say, how to call a given function)
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Today we will continue with graphs, which will take us into next week

Ineffective Sorts

StackSort connects to StackOverflow, searches for 'sort a list', and downloads and runs code snippets until the list is sorted.

xkcd # 1185

Lecture 5: Tuesday, September 9th

PS1 is due tomorrow by 11:59 pm
- The extension system is linked to from the Canvas landing page
- Extensions can be submitted up to 3 days after the (original) due date
PS2 will be out Thursday, due next Wednesday (by 11:59 pm)
- Gradescope submissions open up 72 hours before the due date
PA1 is out today, due next Friday (Sep 19) by 11:59 pm
- Gradescope will open up later this week
- Note that acceptance tests are not the same as the grading tests!
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mon 11-12, Tue 1-2, and Thu 2-3 in Rice 402
- Prof. Floryan’s office hours are Wed 12:30-2 and Thu 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
Today we will continue with graphs, which will take us into next week

Weird Unicode Math Symbols

U+2A0B ⨋ Mathematicians need to calm down

xkcd # 2606

Lecture 4: Thursday, September 4th

PS0 was due yesterday by 11:59 pm
- The extension system is linked to from the Canvas landing page
- Extensions can be submitted up to 3 days after the (original) due date
PS1 will be out today, due next Wednesday (by 11:59 pm)
- Gradescope submissions open up 72 hours before the due date
PA1 will be out… soon
Course textbook link is on the Canvas landing page
Office hours have started, all listed on the Canvas landing page
- Prof. Bloomfield’s office hours are Mondays 11-12, Tuesdays 1-2, and Thursdays 2-3 in Rice 402
- Prof. Floryan’s office hours are Wednesdays 12:30-2 and Thursdays 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - But only 5-7 today!
  - TA pictures linked to from the Canvas landing page
Today we will continue with graphs, which will takes us 4-5 lectures

Complexity Analysis

PERPETUALLY OPTIMISTIC CASE: Early in the execution, our research group makes a breakthrough on proving P=NP.

xkcd # 2939

Lecture 3: Tuesday, September 2nd

PS0 is out in Canvas’ Assignments, and due tomorrow, Wednesday Sep 3, by 11:59 pm
- Gradescope submissions open up 72 hours before the due date
- The extension system is linked to from the Canvas landing page
PS1 will be out this Thursday, and due next Wednesday (Sep 10)
Course textbook link is on the Canvas landing page
Office hours have started:
- Prof. Bloomfield’s office hours are Mondays 11-12, Tuesdays 1-2, and Thursdays 2-3 in Rice 402
- Prof. Floryan’s office hours are Wednesdays 12:30-2 and Thursdays 12:30-2 in room 203
- TA office hours are 5-9, Monday through Thursday, in Rice 442
  - TA pictures linked to from the Canvas landing page
- This is all on the Canvas landing page
Today we will start on graphs, which will takes us 4-5 lectures

Algorithms

There was a schism in 2007, when a sect advocating OpenOffice created a fork of Sunday.xlsx and maintained it independently for several months. The efforts to reconcile the conflicting schedules led to the reinvention, within the cells of the spreadsheet, of modern version control.

xkcd # 1667

Lecture 2: Thursday, August 28th

PS0 is out in Canvas’ Assignments, and due next Wednesday (Sep 3) by 11:59 pm
- Gradescope submission opens up 72 hours before the due date
PS1 out next week, due the following Wednesday
Course textbook link is on the Canvas landing page
TA office hours coming soon (we are targeting Mon-Thu, 5pm-9pm)
Prof. Bloomfield’s office hours TBA, and start next week
Prof. Floryan’s office hours start next week, and are Wed 12:30-2 and Thu 12:30-2 in room 203