DSA1 | Week 1
Data Structures: Just Some Structured Data
Logistics
Classes
9PM - 10:30 PM on Tuesdays and Thursdays at (1/102)
Lab
9PM - 10:30 PM on Fridays at (1/102)
Office Hours
Open door policy (i.e, catch me if you can at AB 4/305)
Logistics
Materials
Slides and (usually) notes → Course Webpage
Classes may be recorded: no guarantees!
Lab Assignments, Class Quizzes, Exams
Gradescope
Announcements & Discussions
WhatsApp Group + Course Webpage
Grading policy
Each of the three exams account for 20% of the grade.
The first and last exams will be pen-and-paper exams. The second exam will be a lab exam.
Each non-practice lab will have a collection of tasks worth 2 points (all-or-none grading). The total number of points you can earn through labs is capped at 20, and accounts for 20% of the grade. There are (tentatively) 11 labs that have graded exercises.
A random subset of classes will start with a short quiz based on the material from recent lectures, worth 2 points. The total number of points you can earn through quizzes is capped at 20, and accounts for 20% of the grade. There are (tentatively) 16 quizzes planned for this course.
The are three assignments that are not graded but are recommended for practice.
Attendance will be tracked for classes and labs. However, there are no points for attending.
Timelines
Lab Assignments are due by midnight on Sundays.
Theory Assignments are ungraded and need not be submitted.
Quizzes will take place in-class.
TAs
1. Yash More
2. Viramgami Gaurav
3. Xhitij Choudhary
TOPICS OVerview
Week 1. Introduction + Stable Marriages
Week 2. Sequences and Graphs
Week 3: Dequeues and Cards
Weeks 4 & 5: Euler Tours
Weeks 6, 7, 8 & 9: BFS/DFS & Applications
Weeks 10: Sorting Algorithms, Asymptotics
Weeks 11, 12, 13 & 14: Heaps, Trees & Search
Weeks 15 & 16: Balanced BSTs
Data Structures
Structured Data
You may remember some so-called primitive data types from your programming courses.
Booleans (true/false)
Numbers (integers, floating point, etc.)
Characters and Strings
Etc.
You may also remember combining and manipulating these values for getting things done.
Expressions
Conditionals
Loops
Etc.
Structured Data
We are going to be doing more of this!
Start out with goals: things you want to do.
Think through the mechanics what you want to do.
Work out what would be the most useful way to store information to aid the mechanics.
Structured Data
We are going to be doing more of this!
Goal: Ace this class
Think through the mechanics what you want to do.
Work out what would be the most useful way to store information to aid the mechanics.
Structured Data
We are going to be doing more of this!
Goal: Ace this class
Study the night of the exam.
Work out what would be the most useful way to store information to aid the mechanics.
Structured Data
We are going to be doing more of this!
Goal: Ace this class
Study the night of the exam.
Maintain notes that will help you digest several weeks of material in a few hours.
Structured Data
We are going to be doing more of this!
Goal: Enjoy college life, YOLO
Study the night of the exam.
Maintain notes that will help you digest several weeks of material in a few hours.
Structured Data
We are going to be doing more of this!
Goal: Enjoy college life, YOLO
Never look at notes 👀
Maintain notes that will help you digest several weeks of material in a few hours.
Structured Data
We are going to be doing more of this!
Goal: Enjoy college life, YOLO
Never look at notes 👀
[Nothing to do.]
Structured Data
We are going to be doing more of this!
Goal: Enjoy college life, YOLO
Never look at notes 👀
[Nothing to do.]
Structured Data
We are going to be doing more of this!
Goal: Enjoy college life, YOLO
Never look at notes 👀
[Nothing to do.]
Structured Data
How you store data depends on what you want to do with it!
Clothes in your cupboard
Structured Data
Suppose you want to represent the polynomial
\(x^2 - 7x + 12\)
Polynomials
How will you talk to your program
about this object?
I pick a number from 1-10.
The Game of 100
You pick a number from the next 10 numbers.
We go on like this until someone reaches 100.
First player to reach 100 wins.
Suppose you have 52 cards.
Storing a hand from a deck
You want to maintain a hand of five cards.
Given a card you want to know if it is in the hand.
You want to be able to add/remove/replace cards in the hand.
A Rubik Cube has six sides, and 9 squares on each side.
Solving a Cube
8 corner cubes, 12 edge cubes, 6 more cubes:
one in the center of each face,
and 1 cube (which doesn't actually exist
Given a shuffled state, you want to solve the cube.
The Game of Trust
my_points = 0
user_points = 0
user_move_1 = input("Input 1 for Cooperate and 0 for Cheat.")
#Sanity check input:
if(user_move_1 != 1 and user_move_1 != 0):
express disappointment and abort
##My first move is to cooperate:
my_points += -1
user_points += 3
if(user_move_1):
my_points += 3
user_points -= 1Majority Mover
This player looks at your entire game history, and:
-
cooperates if you have cooperated more than you have cheated,
-
cheats if you have cheated more than you have cooperated,
-
and acts randomly otherwise.
Random Player
This one chooses a number K between 1 and N uniformly at random,
(where N is the number of rounds played so far)
and mimics the other player's Kth move.
Some more logistics
Notes: https://dsanotes.netlify.app/
Email: neeldhara.m@iitgn.ac.in
Slides: https://slides.com/neeldhara/es242-wXX
XX = 01,02,...,15
The story, all names, characters, and incidents portrayed in this class are fictitious.
No identification with actual persons is intended or should be inferred.
The
Stable Marriage
Problem
Blocking Pairs
When A is matched to B
and X is matched to Y
but A prefers Y over B
and Y prefers A over X.
Goal: Stable Marriage
An assignment with
no blocking pairs.
A Greedy Approach
A strategy for the men: try their best
A strategy for the women: pick the best choice
algorithm stable_matching is
Initialize m ∈ M and w ∈ W to free
while ∃ free man m who has a woman w to propose to do
w := first woman on m's list to whom m has not yet proposed
if ∃ some pair (m', w) then
if w prefers m to m' then
m' becomes free
(m, w) become engaged
end if
else
(m, w) become engaged
end if
repeat
Men = [n] & Women = [n]
ManPref[m, j] is the identity of the j-th ranked woman in m’s preference list
WomanPref[w, j] is the identity of the jth
ranked man in w’s preference list.
Next[w] → the rank of the best unproposed man for w.
Current[m] → is the identity of the woman m is currently
engaged to and is −1 otherwise
FreeWomenList is the set of unmatched women.
Rank is an n ×n 2D array such that Rank[m,w] is the rank of w in m’s preference list.
To begin with, all women are free (aka, single).
Initialize the best option of woman i to the first position.
Initialize the current matched partner of man i to nobody.
Initialize rank information.
w is a free woman
w is a free woman
Confirm that w is for real.
Check that w has someone left to propose to.
w is a free woman
Confirm that w is for real.
Check that w has someone left to propose to.
m is the best unproposed man for w
w is a free woman
Confirm that w is for real.
Check that w has someone left to propose to.
m is the best unproposed man for w
w' is the current matched partner of m
m is currently free.
match m to w
i.e, m accepts w's proposal
m is currently engaged to w'.
m has a better matched partner in w' compared to w
so, m rejects the proposal from w
and w remains single.
m has a better offer in w compared to his current matched partner w'
so, m accepts the proposal from w
and w goes back to being single.
Book-keeping
Update the position of the best choice for w.
Update w to the next woman who is single.
2023 DSA1 | Week 1
By Neeldhara Misra
2023 DSA1 | Week 1
Data Structures: Just some Structured Data
