CS252 Algorithms
Monday, 12 September 2022

https://cs.carleton.edu/faculty/jondich/courses/cs252_f22/

+ Hi!
- Jeff, Olin 301A, jondich
- Office Hours: 301A + Zoom
    see my Carleton-only Google doc w/ Zoom link
    that I mostly remember to turn on
- Masks in Olin and here

+ Moodle & the course website: what's the deal?

+ Prefect: Lily Haas

+ Where we're heading
- *Articulating computational problems
    clearly, precisely, formally
- Devising algorithms to solve those problems
    and *articulating the solutions
    clearly, precisely, formally
- Analyzing algorithms
    runtime, memory use, correctness
- Important classes of algorithms
    greedy, divide-and-conquer, dynamic programming...
- (Not intractability--that's in CS254 Comp & Comp)

* This is in part a writing class, with a
    specialized audience

+ Articulating a computational problem
- Pick a problem that is solved algorithmically in
    software/hardware that you use
- What are the inputs?
- What are the outputs, and what relationship
    do they bear to the inputs?


- Internet search
    in: search string, user's search history,
        GPS coords of browser, time, possible results (all the URLs),
        cookies, ad ID, user metadata, results of google-bot crawling
        (which pages point to which other artifacts)

- The word game "ghost"
    (what problem are we solving?)(AI's optimal strategy)
    in: current word; dictionary; whose turn; number of players
        ...fix this...
    out: 

- YouTube recommendation
    in: data about user's video watching history
        data about current popularity of videos
        likes, etc.
        what videos are there?
    out: list of videos to recommend
        that optimizes something? (goal biz-wise: engagement time;
                                   computationally--what's the proxy?)
        

- Google maps (route-finding)
    in: start and end point
        traffic info
        current location
        mode of transportation
        road information (where's the road; intersections;...) (i.e. the map)

+ Coming up this week
- Getting our homework and communication system
    up and running
- First problem set
    - Articulate the problem formally
        (assuming it's only informal in the problem statement)
    - Devise and articulate a solution
    - Analyze your solution
    - Repeat
- Using LaTeX
- "Review" of computational complexity
    - O, Ω, ϴ
    - worst-case analysis
    - common complexity classes (e.g., O(n log n))

+ For Wednesday
- Two readings and reading responses