Lecture 18 CSE 331 Oct 12, 2012

HW 5 due today Q1, Q2 and Q3 in different piles I will not take any HW after 1:15pm

Other HW related stuff Graded HW4 starting Monday Solutions to HW 5 at the end of the lecture

On Thursday, Oct 18 hours-a-thon Zihe: 3:00-5:00 (Davis 302) Jiun-Jie: 5:00-6:00 (Davis 302) Unclaimed HWs and solutions Unclaimed HWs and solutions

Review Session on Oct 19 Zihe’s recitation section from 9-9:50am in 114 Hoch

Mid term Next Friday in class at 1pm Unfortunately I won’t be there Jiun-Jie with my student Jesse & another PhD student Dung will proctor the exam

On Mon and Wed Jesse will present the lectures If time permits, he will go over the sample mid term on Wed

HW 5 due today Q1, Q2 and Q3 in different piles I will not take any HW after 1:15pm

Main Steps in Algorithm Design Problem Statement Algorithm Problem Definition “Implementation” Analysis n! Correctness+Runtime Analysis Data Structures

Where do graphs fit in? Problem Statement Algorithm Problem Definition “Implementation” Analysis Correctness+Runtime Analysis Data Structures A tool to define problems

Rest of the course Problem Statement Algorithm Problem Definition “Implementation” Analysis Correctness+Runtime Analysis Data Structures Three general techniques

Greedy algorithms Build the final solution piece by piece Being short sighted on each piece Never undo a decision Know when you see it

End of Semester blues MondayTuesdayWednesdayThursdayFriday Project 331 homework 331 HW Exam study Party! Write up a term paper Can only do one thing at any day: what is the maximum number of tasks that you can do?

Greedily solve your blues! MondayTuesdayWednesdayThursdayFriday Project 331 HW Exam study Party! Write up a term paper Arrange tasks in some order and iteratively pick non- overlapping tasks

Ordering is crucial MondayTuesdayWednesdayThursdayFriday Project 331 HW Exam study Party! Write up a term paper Order by starting time Algo =1

Another attempt MondayTuesdayWednesdayThursdayFriday Order by duration Algo =1 Ordering by least conflicts doesn’t work

The final algorithm MondayTuesdayWednesdayThursdayFriday Project 331 HW Exam study Party! Write up a term paper Order tasks by their END time

Questions?

Today’s agenda Prove the correctness of the algorithm

Formal Algorithm R: set of requests Set A to be the empty set While R is not empty Choose i in R with the earliest finish time Add i to A Remove all requests that conflict with i from R Return A