DADS1 2011 Gerth Stølting Brodal  Introduction to Algorithms and Data Structures  Students: 152  Lectures: 2+2 hours  Use clickers at lectures (new.

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1 dADS1 2011 Gerth Stølting Brodal  Introduction to Algorithms and Data Structures  Students: 152  Lectures: 2+2 hours  Use clickers at lectures (new in 2011)  Theoretical TØ: 3 hours  Weekly mandatory group handins  datLAB: Students prepare handin  Exam: Mix of multiple-choice & one-liners

2 dADS1 2011 – clicker experiences Gerth Stølting Brodal  Slides on course webpage – no clicker questions  Slides with questions password protected after lecture  Number of questions: ~ 2 per lecture (45 min)  Types of questions  Understanding of definitions  Understanding of algorithms  Constructive  Feedback – always shown to the students  As expected  Converged to wrong answer (good starting point for discussion)  Question badly phrased (back to the drawing board...)  No convergence (to hard?)  Software:  PowerPoint (PresenterView) + TurningPoint AnyWhere (I didn’t manage to embed into PowerPoint)  Use two projectors in auditorium: 1) Background info 2) Question

3 Four examples from dADS1 1.QuickSort Lecture 2.Union-Find lecture 3.Interval tree lecture 4.Amortized analysis lecture... and an example from an UNF talk

4 Is the answer A or B ? a)Answer A b)Answer B c)Don’t know

5 Is the answer A or B ? a)Answer A b)Answer B c)Don’t know

6 Sandsynlighedsteori Baggrund? a)Ingen b)Gymnasiet c)Gymnasiet + Universitetet d)Universitetet e)Andet steds f)Ved ikke

7 Sandsynligheden for at slå krone 1/2

8 Eksperiment Kast en Mønt a)Plat b)Krone c)På højkant d)Ingen mønt

9 Eksperiment Antal kast før man får krone ? 1 2 3 4 5 6 7 8 9 eller flere a)1 b)2 c)3 d)4 e)5 f)6 g)7 h)8 i)9 eller flere

10 a)1 b)2 c)3 d)4 e)5 f)6 g)7 h)8 i)9 eller flere Sætning Forventede antal kast for at få krone = 2 Bevis □ s.s. for i’te kast er krone s.s. for først i-1 kast er plat # kast Eksperiment Antal kast før man får krone ?

11 1st vote a b c d e f g h i 2nd vote a b c d e f g h i Union-Find

12 Interval Tree 1st vote a b c d e f 2nd vote a b c d e f

13 1st vote a b c d e 2nd vote a b c d e Amortized Analysis

14 Google PageRank TM Metode RandomSurfer Start på knude 1 Gentag mange gange: Kast en terning: Hvis den viser 1-5: Vælg en tilfældig pil ud fra knuden ved at kaste en terning hvis 2 udkanter Hvis den viser 6: Kast terningen igen og spring hen til den knude som terningen viser

15 Metode RandomSurfer Start på knude 1 Gentag mange gange: Kast en terning: Hvis den viser 1-5: Vælg en tilfældig pil ud fra knuden ved at kaste en terning hvis 2 udkanter Hvis den viser 6: Kast terningen igen og spring hen til den knude som terningen viser Google PageRank TM

16 Simpel Webgraf — Sandsynlighedsfordeling Skridt123456 01.0000.000 10.0280.8610.028 20.0390.1090.0280.7450.039 3 0.4320.0280.1180.3380.044 40.0390.2990.0280.3880.0770.169 50.0390.4060.0280.2770.1890.060 60.0390.3160.0280.3660.1430.107 70.0390.3730.0280.2910.1800.087 80.0390.3420.0280.3390.1490.103 90.0390.3610.0280.3130.1690.090 100.0390.3480.0280.3290.1580.098 110.0390.3570.0280.3180.1650.094 120.0390.3510.0280.3250.1600.096 130.0390.3550.0280.3200.1630.094 140.0390.3520.0280.3230.1610.096 150.0390.3540.0280.3210.1630.095 160.0390.3530.0280.3230.1620.095 170.0390.3540.0280.3220.1620.095 180.0390.3530.0280.3220.1620.095 190.0390.3530.0280.3220.1620.095 200.0390.3530.0280.3220.1620.095 210.0390.3530.0280.3220.1620.095 220.0390.3530.0280.3220.1620.095 230.0390.3530.0280.3220.1620.095 240.0390.3530.0280.3220.1620.095 250.0390.3530.0280.3220.1620.095

17 My conclusions about using clickers...  Gives students time to understand the important concepts  Helps me reflect on my lectures  Much better feeling where the students are  Use 2-3 hours per double lecture adding slides