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

dADS1 2011 – clicker experiencesGerth 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

Four examples from dADS1

1. QuickSort Lecture2. Union-Find lecture3. Interval tree lecture4. Amortized analysis lecture

... and an example from an UNF talk

Is the answer A or B ?

a) Answer Ab) Answer Bc) Don’t know

Is the answer A or B ?

a) Answer Ab) Answer Bc) Don’t know

Sandsynlighedsteori Baggrund?

a) Ingenb) Gymnasietc) Gymnasiet + Universitetetd) Universitetete) Andet stedsf) Ved ikke

Sandsynligheden for at slå krone1/2

EksperimentKast en Mønt

a) Platb) Kronec) På højkantd) Ingen mønt

EksperimentAntal kast før man får krone ?

12345678

9 eller flere

a) 1b) 2c) 3d) 4e) 5f) 6g) 7h) 8i) 9 eller flere

a) 1b) 2c) 3d) 4e) 5f) 6g) 7h) 8i) 9 eller flere

Sætning

Forventede antal kast for at få krone = 2

Bevis

□

22

1

2

1

2

111

1

i

i

i

i

ii

s.s. for i’te kast er krone s.s. for først i-1 kast er plat# kast

EksperimentAntal kast før man får krone ?

1st vote

abcdefghi

2nd vote

abcdefghi

Union-Find

Interval Tree 1st vote

abcdef

2nd vote

abcdef

1st vote

abcde

2nd vote

abcde

Amortized Analysis

Google PageRankTM

Metode RandomSurferStart på knude 1Gentag mange gange:

Kast en terning:Hvis den viser 1-5:

Vælg en tilfældig pil ud fra knudenved at kaste en terning hvis 2 udkanter

Hvis den viser 6:Kast terningen igen og spring hen til den knude som terningen viser

Metode RandomSurferStart på knude 1Gentag mange gange:

Kast en terning:Hvis den viser 1-5:

Vælg en tilfældig pil ud fra knudenved at kaste en terning hvis 2 udkanter

Hvis den viser 6:Kast terningen igen og spring hen til den knude som terningen viser

Google PageRankTM

Simpel Webgraf — SandsynlighedsfordelingSkridt 1 2 3 4 5 6

0 1.000 0.000 0.000 0.000 0.000 0.0001 0.028 0.861 0.028 0.028 0.028 0.0282 0.039 0.109 0.028 0.745 0.039 0.0393 0.039 0.432 0.028 0.118 0.338 0.0444 0.039 0.299 0.028 0.388 0.077 0.1695 0.039 0.406 0.028 0.277 0.189 0.0606 0.039 0.316 0.028 0.366 0.143 0.1077 0.039 0.373 0.028 0.291 0.180 0.0878 0.039 0.342 0.028 0.339 0.149 0.1039 0.039 0.361 0.028 0.313 0.169 0.090

10 0.039 0.348 0.028 0.329 0.158 0.09811 0.039 0.357 0.028 0.318 0.165 0.09412 0.039 0.351 0.028 0.325 0.160 0.09613 0.039 0.355 0.028 0.320 0.163 0.09414 0.039 0.352 0.028 0.323 0.161 0.09615 0.039 0.354 0.028 0.321 0.163 0.09516 0.039 0.353 0.028 0.323 0.162 0.09517 0.039 0.354 0.028 0.322 0.162 0.09518 0.039 0.353 0.028 0.322 0.162 0.09519 0.039 0.353 0.028 0.322 0.162 0.09520 0.039 0.353 0.028 0.322 0.162 0.09521 0.039 0.353 0.028 0.322 0.162 0.09522 0.039 0.353 0.028 0.322 0.162 0.09523 0.039 0.353 0.028 0.322 0.162 0.09524 0.039 0.353 0.028 0.322 0.162 0.09525 0.039 0.353 0.028 0.322 0.162 0.095

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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