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Lecture 17 CSE 331 Oct 7, 2016
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Homework 5
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Solutions to HW 4 End of the lecture
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Quiz 1 on Monday
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Main Steps in Algorithm Design
Problem Statement Problem Definition n! Algorithm “Implementation” Data Structures Analysis Correctness+Runtime Analysis
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A tool to define problems
Where do graphs fit in? Problem Statement A tool to define problems Problem Definition Algorithm “Implementation” Data Structures Analysis Correctness+Runtime Analysis
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Three general techniques
Rest of the course Problem Statement Problem Definition Three general techniques Algorithm “Implementation” Data Structures Analysis Correctness+Runtime Analysis
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Greedy algorithms Build the final solution piece by piece
Being short sighted on each piece Never undo a decision Know when you see it
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End of Semester blues Can only do one thing at any day: what is the maximum number of tasks that you can do? Write up a term paper Party! 331 homework Exam study 331 HW Project Monday Tuesday Wednesday Thursday Friday
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Greedily solve your blues!
Arrange tasks in some order and iteratively pick non-overlapping tasks Write up a term paper Party! Exam study 331 HW Project Monday Tuesday Wednesday Thursday Friday
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Ordering is crucial Order by starting time Write up a term paper
Algo =1 Party! Exam study 331 HW Project Monday Tuesday Wednesday Thursday Friday
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Ordering by least conflicts doesn’t work
Another attempt Order by duration Ordering by least conflicts doesn’t work Algo =1 Monday Tuesday Wednesday Thursday Friday
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Order tasks by their END time
The final algorithm Order tasks by their END time Write up a term paper Party! Exam study 331 HW Project Monday Tuesday Wednesday Thursday Friday
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Questions?
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Today’s agenda Prove the correctness of the algorithm
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Formal Algorithm R: set of requests Set S to be the empty set
While R is not empty Choose i in R with the earliest finish time Add i to S Remove all requests that conflict with i from R Return S*= S
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