The document discusses abstraction as an important skill for programmers. It provides examples of abstracting card sorting problems to more familiar problems in order to solve them more efficiently. Binary search and Dijkstra's algorithm are given as examples of abstracting problems to ones that have already been solved. The document emphasizes that any problem can be abstracted and that being creative with problems allows one to better understand them from different perspectives.

1. The best programmers I’ve meet
knew how to sort a deck of cards
pretty d*mn well
Tony Tran

2. Story Time ☺

3. Image source: http://www.eyebrowmagazine.com/__data/assets/image/0010/10045/megan_fox_naked_5.jpg

4. What if
• Given: Deck of playing cards
• Goal: To retrieve any card as fast as
possible!
• Constraints: No real constraints, do whatever you want with the cards! Just don’t
be a smart @s*!
WHAT WOULD YOU DO!?!

5. Find me:
Approaches:
1. Do nothing to the deck (Cost: 52 lookups)
Cost is analyzed in worst case scenario.
"Anything that can go wrong will go wrong.“ – Murphy’s Law

6. Approaches:
1. Do nothing to the deck (Cost: 52 lookups)
2. Group cards by suits (Cost: 4+12 = 16 lookups)
3. Group cards by faces (Cost: 12+4 = 16 lookups)

7. Image source: http://www.flickr.com/photos/60601862@N00/942476116/

8. What if
• Given: 99 note cards with a unique
number written on each card.
• Goal: To retrieve any card as fast as
possible!
• Constraints: No real constraints, do whatever you want with the cards! Just don’t
be a smart @s*!
WHAT WOULD YOU DO!?!

9. Find me:
Approaches:
1. Do nothing to the deck (Cost: 99 lookups)
2. Create bins for groups of 100 and just throw the cards into the bin.
Example:
(Cost: 99 lookups)
When given cards:
1,2,3, ,99
bins
Cost is analyzed in worst case scenario.
"Anything that can go wrong will go wrong.“ – Murphy’s Law

10. Find me:
Approaches:
1. Do nothing to the deck (Cost: 99 lookups)
2. Create bins for groups of 100 and just throw the cards into the bin. (Cost: 99 lookups)
3. Sort the deck! Then perform binary search to find
card.
(cost: log2(99) lookups ~= 7 look ups)
Depiction of binary search (does not show entire search)
Cost is analyzed in worst case scenario.
"Anything that can go wrong will go wrong.“ – Murphy’s Law

11. Find me:
Approaches:
1. Do nothing to the deck (Cost: 99 lookups)
2. Create bins for groups of 100 and just throw the cards into the bin. (Cost: 99 lookups)
3. Sort the deck! Then perform binary search to find
card.
(cost: log2(99) lookups ~= 7 look ups)
Depiction of binary search (does not show entire search)
☺
Cost is analyzed in worst case scenario.
"Anything that can go wrong will go wrong.“ – Murphy’s Law

12. How does this apply to
programming?
Abstraction!

13. Key point #1 and #2:
1. Being able to abstract a problem to
something less complex, or more familiar,
will make the problem easier!
2. Abstracting a problem to a problem that
has already been solved is even better!
You don’t really have to do any work!
Image source: http://www.scientificamerican.com/media/inline/3E0F9160-E7F2-99DF-358998AA3C1A910F_1.jpg

14. Other fans of abstraction
What is the shortest path from 1 to any other node?
• “the purpose of abstraction is not to be vague,
but to create a new semantic level in which one
can be absolutely precise.” - Edsger W. Dijkstra

15. INTERNET!!!
“[OSPF] computes the shortest path tree for each route
using a method based on Dijkstra's algorithm, a shortest
path first algorithm.”

16. Keypoint #3
3. There’s no such thing as a dumb problem
Problem: Given a spatula and a dish of pancakes (say 6 for now), how would
you flip the pancakes such that the pancakes become sorted with the largest pancake
at the bottom and smallest at the top? How many steps would it require?
Image source: http://sfist.com/attachments/SFist_Brock/pancakes.jpg

17. Initial State:
GOAL
FLIP

18. Someone familiar:
SORTING PANCAKES == SORTING BY PREFIX REVERSAL
• Bill Gates & Christos Papadimitriou,
Bounds For Sorting By Prefix Reversal.
Discrete Mathematics, vol 27, pp 47-57,
1979.
We referred to bounds as “Costs”

19. Key Points:
1. Being able to abstract a problem to something less complex, or
more familiar, will make the problem easier!
2. Abstracting a problem to a problem that has already been solved is
even better!
3. There’s no such thing as a dumb problem.
4. Be creative and have fun with problems.
You have the ability to create an entire world
at your fingertips!

20. -THANK YOU-
New title proposal:
The best programmers I’ve meet knew how to ABSTRACT PROBLEMS pretty d*mn well
“The hardest part of solving a problem is to completely understand it to
a point where you can see it from many different perspectives and abstractions”
-A very wise T.A.
Thank you,
-Tony Tran
@quicksorter
P.S. My gf will probably be reading this, so the story at the beginning
didn’t really happen 0-=) But really, it didn’t ☺