Unformatted text preview: Lecture 20
CSE 331
Oct 17, 2011 Temp letter grades assigned See the blog post for more details A feedback…
Time pressure on midterm favors “quick thinkers”
Tested different skills than those on HWs Midterm has more weight than the homeworks Need another scribe for today Any volunteer? Algorithm for Interval
Scheduling
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*=A A* is optimal Run time analysis
O(n log n) time sort intervals such that f(i) ≤ f(i+1)
O(n) time build array s[1..n] s.t. s[i] = start time for
i
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*=A Do the
removal on
the fly Algorithm implementation
Go through the intervals in order of their finish time
3
2
1 4 In general, if jth interval is the last one chosen
Pick smallest i>j such that s[i] ≥ f(j) How can you tell
Check if ts[i] <iff(1)
in O(1) ime
any of 2,3 or 4
conflict with 1? O(n log n) run
time The final algo
O(n log n) time sort intervals such that f(i) ≤ f(i+1)
O(n) time build array s[1..n] s.t. s[i] = start time for
i
Add 1 to A and set f = f(1)
For i = 2 .. n
If s[i] ≥ f
Add i to A
Set f = f(i)
Return A* = A Reading Assignment
Sec 4.1of [KT] Questions? The “real” end of Semester
blues
There are deadlines and
durations of tasks Write up a term paper
Party!
Exam study 331 HW
Project Monday Tuesday Wednesday Thursday Friday The “real” end of Semester
blues
There are deadlines and
durations of tasks Write up a term paper
Exam study
Party!
331 HW
Project
Monday Tuesday Wednesday Thursday Friday The algorithmic task
YOU decide when to start each
task Write up a term paper
You have to
do ALL the
tasks Exam study
Party!
331 HW
Project
Monday Tuesday Wednesday Thursday Friday Scheduling to minimize lateness
All the tasks have to be
scheduled
GOAL: minimize maximum
lateness
Write up a term paper
Exam study
Party!
331 HW
Project
Monday Tuesday Wednesday Thursday Friday One possible schedule
All the tasks have to be
scheduled
GOAL: minimize maximum
lateness Lateness = 0 331 HW
Monday Tuesday Lateness = 2
Party! Exam study
Wednesday Thursday Write up a term pa
Friday ...
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This note was uploaded on 12/11/2011 for the course CSE 331 taught by Professor Rudra during the Fall '11 term at SUNY Buffalo.
 Fall '11
 RUDRA

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