Teacher Talk 2011. 1.There has never been a better time to teach Computer Science 2.We can learn...

Teacher Talk2011

1. There has never been a better time to teach Computer Science

2. We can learn from Chemistry, Physics, Biology, …

What am I going to show you?

First, I will use sorting to demonstrate “This is the best time to teach CS”

Second, I will use binary trees (and AVL trees) to show we can do what Chemists do

Sorting, what’s that then?

Given a collection of data, get it into order …



9 2 6 0 4 3 2 7 5

This is NOT in order



0 2 3 4 5 6 7 9

This is IS in order



0 2 3 4 5 6 7 9

This is IS in order

It’s in ascending order


Sorting is the process of going from this

0 2 3 4 5 6 7 9

9 2 6 0 4 3 2 7 5

to that

Sorting, why bother?

9 2 6 0 4 3 2 7 5

Who cares?

You can find things quicker!

Sorting, why bother?

0 2 3 4 5 6 7 9

9 2 6 0 4 3 2 7 5

Who cares?

You can find things quicker!

Use “binary search” (or even linear search and stop early)

Sorting, why bother?Who cares?

Do you remember the telephone directory? Imagine if it was just in any order (random)How long would it take you to find my telephone number?



Do you remember the dictionary?Imagine if that was just in any order.How long would it take to find a word, or to determine if the word was not present?



Do you remember the dictionary?Imagine if that was just in any order.How long would it take to find a word, or to determine if the word was not present?

Do you ever use an online spelling checker?How does that work?


What do you prefer?

Some algorithms for sorting

• bubble sort• insertion sort• selection sort• shell sort• gnome sort• merge sort• quick sort• heap sort• radix sort• bead sort

sorting



sorting

What’s an algorithm?



sorting

quadratic



sorting

logarithmic



sorting

linear



sorting

Our example

Quadratic algorithms

• bubble sort• insertion sort• selection sort

sorting

Bubble Sort

9 2 06 4 3 2 57

Example



sorting

Bubble Sort

9 2 06 4 3 2 57

Example

compare



sorting

Bubble Sort

2 9 06 4 3 2 57

Example

swap



sorting

Bubble Sort

2 9 06 4 3 2 57

Example

compare



sorting

Bubble Sort

2 6 09 4 3 2 57

Example

swap



sorting

Bubble Sort

2 6 09 4 3 2 57

Example

compare



sorting

Bubble Sort

2 6 90 4 3 2 57

Example

swap



sorting

Bubble Sort

2 6 90 4 3 2 57

Example

compare



sorting

Bubble Sort

2 6 40 9 3 2 57

Example

swap



sorting

Bubble Sort

2 6 40 9 3 2 57

Example

compare



sorting

Bubble Sort

2 6 40 3 9 2 57

Example

swap



sorting

Bubble Sort

2 6 40 3 9 2 57

Example

compare



sorting

Bubble Sort

2 6 40 3 2 9 57

Example

swap



sorting

Bubble Sort

2 6 40 3 2 9 57

Example

compare



sorting

Bubble Sort

2 6 40 3 2 7 59

Example

swap



sorting

Bubble Sort

2 6 40 3 2 7 59

Example

compare



sorting

Bubble Sort

2 6 40 3 2 7 95

Example

swap



sorting

Bubble Sort

2 6 40 3 2 7 95

Example



sorting

Bubble Sort

2 6 40 3 2 7 95

Example

compare



sorting

Bubble Sort

2 0 46 3 2 7 95

Example

swap



sorting

Bubble Sort

2 0 46 3 2 7 95

Example

compare



sorting

Bubble Sort

2 0 64 3 2 7 95

Example

swap



sorting

Bubble Sort

2 0 64 3 2 7 95

Example

compare



sorting

Bubble Sort

2 0 34 6 2 7 95

Example

swap



sorting

Bubble Sort

2 0 34 6 2 7 95

Example

compare



sorting

Bubble Sort

2 0 34 2 6 7 95

Example

swap



sorting

Bubble Sort

2 0 34 2 6 7 95

Example

compare



sorting

Bubble Sort

2 0 34 2 6 5 97

Example

swap



sorting

Bubble Sort

2 0 34 2 6 5 97

Example



sorting

Bubble Sort

2 0 34 2 6 5 97

Example

Are you tired yet? Bored?



sorting

Bubble Sort

2 0 34 2 6 5 97

Example

compare



sorting

Bubble Sort

0 2 34 2 6 5 97

Example

swap



sorting

Bubble Sort

0 2 34 2 6 5 97

Example

compare



sorting

Bubble Sort

0 2 43 2 6 5 97

Example

swap



sorting

Bubble Sort

0 2 43 2 6 5 97

Example

compare



sorting

Bubble Sort

0 2 23 4 6 5 97

Example

swap



sorting

Bubble Sort

0 2 23 4 6 5 97

Example

compare



sorting

Bubble Sort

0 2 23 4 5 6 97

Example

swap



sorting

Bubble Sort

0 2 23 4 5 6 97

Example



sorting

Bubble Sort

0 2 23 4 5 6 97

Example

compare



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

swap



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare



sorting

Bubble Sort

0 2 32 4 5 6 97

Example



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare



sorting

Bubble Sort

0 2 32 4 5 6 97

Example



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

Phew!



sorting

Bubble Sort

On an Array



sorting

Bubble Sort

9 2 06 4 3 2 57

Example

i=8



sorting

Bubble Sort

9 2 06 4 3 2 57

Example

compare

i=8j=0



sorting

Bubble Sort

2 9 06 4 3 2 57

Example

swap

Example

i=8j=0



sorting

Bubble Sort

2 9 06 4 3 2 57

Example

compare

ExampleExample

i=8j=1



sorting

Bubble Sort

2 6 09 4 3 2 57

Example

swap

ExampleExampleExample

i=8j=1



sorting

Bubble Sort

2 6 09 4 3 2 57

Example

compare

ExampleExampleExampleExample

i=8j=2



sorting

Bubble Sort

2 6 90 4 3 2 57

Example

swap

ExampleExampleExampleExampleExample

i=8j=2



sorting

Bubble Sort

2 6 90 4 3 2 57

Example

compare

ExampleExampleExampleExampleExampleExample

i=8j=3



sorting

Bubble Sort

2 6 40 9 3 2 57

Example

swap

ExampleExampleExampleExampleExampleExampleExample

i=8j=3



sorting

Bubble Sort

2 6 40 9 3 2 57

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExample

i=8j=4



sorting

Bubble Sort

2 6 40 3 9 2 57

Example

swap

ExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=4



sorting

Bubble Sort

2 6 40 3 9 2 57

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=5



sorting

Bubble Sort

2 6 40 3 2 9 57

Example

swap

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=5



sorting

Bubble Sort

2 6 40 3 2 9 57

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=6



sorting

Bubble Sort

2 6 40 3 2 7 59

Example

swap

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=6



sorting

Bubble Sort

2 6 40 3 2 7 59

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=7



sorting

Bubble Sort

2 6 40 3 2 7 95

Example

swap

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=8j=7



sorting

Bubble Sort

2 6 40 3 2 7 95

Example sortingExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample



sorting

Bubble Sort

2 6 40 3 2 7 95

Example

compare

sortingExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=7j=0



sorting

Bubble Sort

2 6 40 3 2 7 95

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=7j=1



sorting

Bubble Sort

2 0 46 3 2 7 95

Example

swap

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=7j=1



sorting

Bubble Sort

2 0 46 3 2 7 95

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=7j=2



sorting

Bubble Sort

2 0 64 3 2 7 95

Example

swap

sortingExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=7j=2



sorting

Bubble Sort

2 0 64 3 2 7 95

Example

compare


i=7j=3



sorting

Bubble Sort

2 0 34 6 2 7 95

Example

swap


i=7j=3



sorting

Bubble Sort

2 0 34 6 2 7 95

Example

compare


i=7j=4



sorting

Bubble Sort

2 0 34 2 6 7 95

Example

swap


i=7j=4



sorting

Bubble Sort

2 0 34 2 6 7 95

Example

compare


i=7j=5



sorting

Bubble Sort

2 0 34 2 6 7 95

Example

compare


i=7j=6



sorting

Bubble Sort

2 0 34 2 6 5 97

Example

swap


i=7j=6



sorting

Bubble Sort

2 0 34 2 6 5 97

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample



sorting

Bubble Sort

2 0 34 2 6 5 97

Example

compare


i=6j=0



sorting

Bubble Sort

0 2 34 2 6 5 97

Example

swap

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=6j=0



sorting

Bubble Sort

0 2 34 2 6 5 97

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=6j=1



sorting

Bubble Sort

0 2 34 2 6 5 97

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=6j=2



sorting

Bubble Sort

0 2 43 2 6 5 97

Example

swap


i=6j=2



sorting

Bubble Sort

0 2 43 2 6 5 97

Example

compare


i=6j=3



sorting

Bubble Sort

0 2 23 4 6 5 97

Example

swap


i=6j=3



sorting

Bubble Sort

0 2 23 4 6 5 97

Example

compare


i=6j=4



sorting

Bubble Sort

0 2 23 4 6 5 97

Example

compare


i=6j=5



sorting

Bubble Sort

0 2 23 4 5 6 97

Example

swap


i=6j=5



sorting

Bubble Sort

0 2 23 4 5 6 97

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample



sorting

Bubble Sort

0 2 23 4 5 6 97

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=5j=0



sorting

Bubble Sort

0 2 23 4 5 6 97

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=5j=1



sorting

Bubble Sort

0 2 23 4 5 6 97

Example

compare


i=5j=2



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

swap


i=5j=2



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare


i=5j=3



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare


i=5j=4



sorting

Bubble Sort

0 2 32 4 5 6 97

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=4j=0



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample

i=4j=1



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare


i=4j=2



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

compare


i=4j=3



sorting

Bubble Sort

0 2 32 4 5 6 97

ExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExampleExample



sorting

Bubble Sort

0 2 32 4 5 6 97

Example



sorting

Bubble Sort

0 2 32 4 5 6 97

Example

Phew!



sorting

Bubble Sort

On an Array

Can we visualize this?



sorting

Bubble Sort

On an Array


Assume we have a random list of numbers from 0 to n-1, put in an array ASuch that A[0] is the 1st number and A[n-1] is the last



sorting

Bubble Sort

On an Array



9 2 06 4 3 2 57



sorting

Bubble Sort

On an Array



9 2 06 4 3 2 57

A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8]



sorting

Bubble Sort

On an Array



9 2 06 4 3 2 57

A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8]

We could plot A[i] on a graph as a point with x/y coordinates i/A[i]



sorting

Bubble Sort

On an Array



9 2 06 4 3 2 57

A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8]


Do this as the algorithm progress to see how it progresses.



sorting

Bubble Sort

On an Array



9 2 06 4 3 2 57

A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8]


Do this as the algorithm progress to see how it progresses.

Ready?



sorting

Bubble Sort

On an Array

sorting

Bubble Sort

Show me more!

sorting

Bubble Sort

Show me more!

• different sorting algorithms and relative performance• a beauty contest

• what is the “sound” of sorting?• can you show me it by mime? Expressive dance?

sorting

Bubble Sort

NOTE to self:Bubble sort is a quadratic time algorithm.If I have to sort a data set of N objects the run time will be proportional to N2

sorting

Bubble Sort


To sort 10 numbers will take 100 units of time

sorting

Bubble Sort


To sort 10 numbers will take 100 units of timeTo sort 100 numbers will take 10,000 units of time

sorting

Bubble Sort


To sort 10 numbers will take 100 units of timeTo sort 100 numbers will take 10,000 units of timeTo sort 1000 numbers will take 1,000,000 units of time

Links

• sorting algorithm animation• sound of sorting (part 1)• sound of sorting (part 2)• bubble sort by folk dancing

http://www.sorting-algorithms.com/

http://www.youtube.com/watch?v=t8g-iYGHpEA&feature=player_embedded

http://www.youtube.com/watch?v=iXAjiDQbPSw&feature=player_embedded

http://www.youtube.com/watch?v=lyZQPjUT5B4

Barak on Sorting

http://www.youtube.com/watch?v=k4RRi_ntQc8&feature=related

I think there has never been a better time to teach Computer Science

end of part 1

Live dangerously … live like a teacher, like a Physics teacher,or Chemistry, or Biology, or …

Balanced binary trees … without powerpoint

Binary search trees and AVL trees

http://webdiis.unizar.es/asignaturas/EDA/AVLTree/avltree.html

Live dangerously

Teacher Talk 2011. 1.There has never been a better time to teach Computer Science 2.We can learn...

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