Lecture 3

CSE 331Sep 3, 2010

Remember: Stick with your group

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Upcoming deadlines

Sep 7: Form your group (email me the full names)

Sep 10: Teams can swap members

Don Knuth

Don Knuth Reward Checks

http://www.flickr.com/photos/32184482@N03/3010989157/

Questions/Comments?

What are Algorithms?

A series of steps designed to solve a problem

A geometric way of solving problems

An abstract mathematical solution for a problem

Knuth’s Definition

An algorithm is a finite, definitive, effectiveprocedure with some input and some output

Why care about algorithms- II

Driving directions

Why care about algorithms- II

Computing Bestsellers on the fly

Why care about algorithms- II

Booking cheapest air tickets

Why care about algorithms- II

Google searches

Why care about algorithms- II

Data compression

http://www.di.ens.fr/~cherniav/teaching.html

Why care about algorithms- II

Error correction

http://www.switched.com/2010/02/11/fix-dvd-scratches-using-a-banana-and-toothpaste/

(And I could) go on…

http://www.movieposter.com/poster/MPW-33672/Titanic.html

Read Chazelle’s article

Questions/Comments?

From problem to software

Main Steps in Algorithm DesignProblem StatementProblem Statement

AlgorithmAlgorithm

Real world problem

Problem DefinitionProblem Definition Precise mathematical def

“Implementation”“Implementation” Data Structures

AnalysisAnalysis Correctness/Run time

Worst-case analysis

Correctness should hold for every valid input

Resource usage by the worst-possible input

What resources?

What resources?

Why worst-case?Why worst-case?

The language of proofs

Brad Pitt had a beard

Every goat has a beard

waleg.com

animaldiversity.org

Hence, Brad Pitt is a goat.Hence, Brad Pitt is a goat.

Questions/Comments?

National Resident Matching

(Screen) Docs are coming to BUF

Hawkeye (M*A*S*H)

JD (Scrubs)

Buffalo General

Millard Filmore (Gates Circle)

Millard Filmore (Suburban)

What can go wrong?

The situation is unstable!

What happens in real life

PreferencesPreferences

InformationInformation

PreferencesPreferences

NRMP plays matchmaker

Stable Marriage Problem

David Gale Lloyd Shapley