acm today some nice unix commands… practice problems? code.google.com/codejam/ this week: beyond...

ACM today

Some nice unix commands…

practice problems? code.google.com/codejam/

This week: beyond Floyd-

Warshall

top screen nice

Make sure long-running programs are nice !

top watches the progress of all of knuth's processes.

What are are all of these columns saying?

Creates a terminal session independent of a particular connection

screen

particularly this one…

nice!

screenscreen -r

to startto resume

nice java args +19

Upcoming schedule…

Sep 29 Discussion session on new problems: 4 problems

Oct 6 Lab session: 4 problems

Oct 13 Discussion session on new problems: 4 problems Oct 20 Lab / mock ACM contest, 9pm – 1:00am, 6 problems

Oct 27 No class… ACM's fall break…

Nov 3 Meeting with HMC teams going to contest

Nov 7 Contest @ Riverside

Nov 17 Discussion and wrap-up for the semester

You may submit problems until the end of exams…

This week's problems…

Read over these problems:

Rank in terms of difficulty

… and approach.

Current Jotto standings…

Sophs Jrs Srs Others

icily 0 icily 0 icily 1 icily 1

strep 2 strep 2 strep 2 strep 1

spork 1 spork 3 spork 0 spork 0

spend 2 spend 2 spend ? spend 2

peeps 2 peeps 1 peeps ? peeps 1

furls 1 furls 1 furls ? furls 1

I'd call this a "senior moment"

MST

Minimum spanning tree: (Prim’s algorithm)

Start anywhere and repeatedly choose the next-smallest edge out

from your current tree.

MST

Minimum spanning tree: (Prim’s algorithm)

Start anywhere and repeatedly choose the next-smallest edge out

from your current tree.

Done!

The other three problems…

can all be solved with Max Flow

Max Flow

A

B

E

D

C13

F

16

10 4 9

12

14

7

20

4source

capacity

sink

The problem how much traffic can get from the source to the sink ?

Ford-Fulkerson algorithm

http://www-b2.is.tokushima-u.ac.jp/~ikeda/suuri/maxflow/MaxflowApp.shtml?demo1Some animations:

http://www.lix.polytechnique.fr/~durr/MaxFlow/

Max FlowThe problem how much traffic can get from the source to the sink ?

A

B

E

D

C13

AB

C

D

E

FROM

A B C D E

F

- 16 13 - -- - 10 12 -

- 4 - - 14

- - 9 - -

- - - 7 -

--

-

20

4

- - - - - -F

F

16

10 4 9

12

14

7

20

4

TO

“Capacity Graph”

source

sink

capacity C

Find a path in C via BFSThe problem how much traffic can get from the source to the sink ?

A

B

E

D

C13

FROM

F

- 16 13 - -- - 10 12 -

- 4 - - 14

- - 9 - -

- - - 7 -

--

-

20

4

- - - - - -

16

10 4 9

12

14

7

20

4

TO

source

sink

capacity CAB

C

D

E

A B C D E

F

F

need to add this into here…

Create FCreate a FLOW GRAPH with the minimum weight from that

path

A

B

E

D

C13

AB

C

D

E

FROM

A B C D E

F

- 12 0 - --12

- 0 12 -

- 0 - - 0

- -12

0 - -

- - - 0 -

--

-

12

0

- - - -12

- -F

F

16

10 4 9

12

14

7

20

4

TO

“Flow Graph”

source

sink

capacity F

12

12

12

flow in one direction is negative flow in the other direction

R = C - FCreate a RESIDUAL GRAPH with the rest of the capacity

after that flow

A

B

E

D

C13

AB

C

D

E

FROM

A B C D E

F

F

F

4

10 4 9

0

14

7

8

4

TO

“Residual Graph”

source

sink

capacity R

12 12

reverse edges allow the "undoing" of previous flow!

12

- 4 13 - -12 - 10 0 -

- 4 - - 14

- 12 9 - -

- - - 7 -

--

-

8

4

- - - 12 - -

Keep going!Continue running this on the residual capacity until BFS

fails…

A

B

E

D

C12/13

F

11/16

0/10

1/4

0/9

12/12

11/14

7/7

19/20

4/4

source

sink

There is no longer a path from A to F !

max flow: 23

The max flow algorithm

A

B

E

D

C13

F

16

10 4 9

12

14

7

20

4

“Residual Graph”

source

sink

capacity

4

3

2

1

5

2

2

10

4

flow

Don't need to keep R around explicity: Keep only the current flow (F) and the

original capacity (C).A

B

C

D

EF

2

18

4

3 residual

9

5

9

72592

11

124

61

Floyd-Fulkerson

1. Set F to all 02. Compute R = C - F3. BFS in R from source to sink.3a. If no path, you’re done. 3b. If a path, add the available

capacity to F; goto (2).

Get into the flow!

def max_flow(C, source, sink): n = len(C) # C is the capacity matrix F = [[0] * n for i in range(n)] # F is the flow matrix # residual capacity from u to v is C[u][v] - F[u][v]

while True: path = BFS(C, F, source, sink) if not path: break # no path - we're done!

flow = 9042 # a big number ~ inf. for u,v in path: # find bottleneck flow = min(flow, C[u][v] - F[u][v]) print "Augmenting by", flow for u,v in path: # traverse path to update flow F[u][v] += flow # forward edge up F[v][u] -= flow # backward edge down

return sum([F[source][i] for i in range(n)])

A little bit of name contention…

edmonds_karpThis is the algorithm.

Useful alone, too

def BFS(C, F, source, sink): queue = [source] # the BFS queue paths = {source: []} # dictionary of partial paths while queue:

u = queue.pop(0) # next node to explore (expand) for v in range(len(C)): # for each possible next node

# path from u to v? and not yet at v? if C[u][v] - F[u][v] > 0 and v not in paths: paths[v] = paths[u] + [(u,v)] if v == sink: return paths[v]

queue.append(v) # go from v in the future return None

A brief BFS algorithm using the Capacity matrix

Setting up…

if __name__ == "__main__":

# make a capacity graph # node A B C D E F C = [ [ 00, 16, 13, 00, 00, 00 ], # A [ 00, 00, 10, 12, 00, 00 ], # B [ 00, 04, 00, 00, 14, 00 ], # C [ 00, 00, 9, 00, 00, 20 ], # D [ 00, 00, 00, 7, 00, 4 ], # E [ 00, 00, 00, 00, 00, 00 ] ] # F

print "C is", C source = 0 # A sink = 5 # F

max_flow_value = max_flow( C, source, sink ) print "max_flow_value is", max_flow_value

And the code needed to run it…

Linked at the ACM website by the slides…

Max Flow

Given that nodes are searched alphabetically, what flow amounts will be added next ?

http://www-b2.is.tokushima-u.ac.jp/~ikeda/suuri/maxflow/MaxflowApp.shtml?demo1Some animations:

http://www.lix.polytechnique.fr/~durr/MaxFlow/

A

B

E

D

C13

F

16

10 4 9

12

14

7

20

4source

capacity

12

12

12

The challenge:

setting up the MaxFlow graph

dinner

4 54 5 3 53 5 2 6 44 54 5 3 53 5 2 6 30 0

number of teams Input

Output

number of tables

# of people in each team

can an assignment be made without putting teammates

together?

01

capacity of each table

again…

end…

35

2 6 3

tables with capacities

teams with sizes

53

4

5

seating assignments!

no teammates

patrol

6 71 22 61 33 43 54 65 6

number of fields Input

Output

number of paths

there is a path from field 1 to field 2

smallest # of fields that need to be patrolled so that a round trip is NOT possible (without detection)

1

1 6

2

34

5

start (farm) goal (ice cream)

Bessie must make a round trip without revisiting any nodes…

4 3 32 2 1 2 3 12 2 2 3 1 22 2 1 3 1 22 1 1 3 3

number of cows

Input

total # of foods

total # of drinks

# of foods cow[i] likes

# of drinks cow[i] likesfoods drinks

0

Output

# of cows that can receive both a food and a

drink they like…

3

each can be used only once

Likes

foods drinks

1

2

3

1 2

2 3

1 3

1 3

3 1

1 2

1 2

3What is a cow-satisfying assignment here?

dining

number of classes

Input

# of cows (edges)

edge from class 1 to class 2

Output

smallest number of projectors needed to cover all classes

2

class are scheduled sequentially…

project

4 41 22 32 41 4

other edges

1 2 3 4

See you next week!

Max flow examples…

Dinner problem

Circuses problem

A

E

C

F

D

B

G

Circus inspectors need to visit every circus --

starting from anywhere.

What is the smallest # of inspectors needed

to visit each node without overlap?

There are

M teams with M[i] team members

T tables with T[i] seating capacity

No two members from one team should share a table. Can you still seat everyone?

35

2 6 3

tables with capacities

team sizes

4 5 3 5

Martin's approach…

Can we compute M10 faster?

100x100 bit matrix

completed at

9

and some others, perhaps

submitted during the lab session…

Moo U.

3 2 12 2 11 11 2

2

Input

Output

# of students

maximum number of students that can

be fed!

# of toppings available

# of toppings on each pizza

student 1 likes 2

toppings: #2 and #1

The CS 5 pizza

problem!

student 2 likes 1

topping: #1

student 3 likes 1

topping: #2

Bipartite Matching

…

studentspizzas

up to 1,000

up to 30-choose-15

A greedy approach works

here!

The Marriage Problem

Start with some matching (in red)

Find an “augmenting path”

From an open vertex in one set to an open vertex in the other setwith alternating edges in the current matching (in red)This augmenting path produces a larger match!

Max flow / min cut

…

studentspizzas

up to 1,000

up to 30-choose-15

sourcesink

preferences…

1

1

11

1

1

1

11

1

1

1

1

What is the largest network flow this graph

will allow?

This week

Look over these two problems…

Ideas?

grain

5113411

10

Input

Output

# of weights

smallest value that can not be formed from a subset of the

weights

weights

Where are the dead spots?

fliptile

4 41 0 0 10 1 1 00 1 1 01 0 0 1 0 0 0 0

1 0 0 11 0 0 10 0 0 0

Input

Output

size of board

moves to make to turn all of the

lights offstarting state of the

lights (tiles)

Lights Out!

http://www.csm.ornl.gov/~geist/java/applets/lightsout/

(lexicographically minimal)

Linear algebra approach?http://mathworld.wolfram.com/LightsOutPuzzle.html

Each move flips its own tile and its

4-neighbors…

This week

Returning to the other two…

This week

ACM this week: graphs

Graph problems, take 1Today:

Graph-algorithm matching challenge

Floyd-Warshall all-pairs shortest pathsEdgar Dijkstra single-source shortest pathsFord-Fulkerson max-flow min-cut

Bellman Ford single-source shortest pathsPrim minimum spanning treeKruskal minimum spanning tree

name problem

ACM this week

Today:

Minimum spanning tree:

Given a graph, find the minimum-weight tree within

it.

Minimum spanning tree political mantra:

Graph problems and geometric algorithms, take 1

ACM this week

Today:

Minimum spanning tree:

Given a graph, find the minimum-weight tree within

it.

Minimum spanning tree political mantra:

Greed is good!

Graph problems and geometric algorithms, take 1

ACM this week: graphs

Graph problems, take 1Today:

Graph-algorithm matching challenge

Floyd-Warshall all-pairs shortest pathsEdgar Dijkstra single-source shortest pathsFord-Fulkerson max-flow min-cut

Bellman Ford single-source shortest pathsPrim minimum spanning treeKruskal minimum spanning tree

name problem

All-pairs shortest paths

A

B

ED

C

8

13

1

6

12

9

7 0

11

0 8 13 - 1- 0 - 6 12

- 9 0 - -

7 - 0 0 -

- - - 11 0

AB

C

D

E

A B C D E

from

to

“Floyd-Warshall algorithm”

D0 = (dij )

0

dij = shortest distance from i to j through nodes {1, …, k}

k

dij = shortest distance from i to j through no nodes

0

Adjacency Matrix

All-pairs shortest paths...

D0 = (dij )

0

0 8 13 - 1- 0 - 6 12

- 9 0 - -

7 - 0 0 -

- - - 11 0

dij = shortest distance from i to j through {1, …, k}

k


BeforeAB

C

D

E

A B C D E

D1 = (dij )

1

0 8 13 - 1- 0 - 6 12

- 9 0 - -

7 15 0 0 8

- - - 11 0

AfterAB

C

D

E

A B C D E


D0 = (dij )

0

0 8 13 - 1- 0 - 6 12

- 9 0 - -

7 - 0 0 -

- - - 11 0

AB

C

D

E

D1 = (dij )

1

dij = shortest distance from i to j through {1, …, k}

k

0 8 13 - 1- 0 - 6 12

- 9 0 - -

7 15 0 0 8

- - - 11 0


Before AfterAB

C

D

E

A B C D E

AB

C

D

E

A B C D E

+ )

dij

=

k dij

k-1, dik

k-1 dkj

k-1min(


0 8 13 14 1- 0 - 6 12

- 9 0 15 21

7 15 0 0 8

- - - 11 0

AB

C

D

E

D2 = (dij )

2

0 8 13 14 1- 0 - 6 12

- 9 0 15 21

7 9 0 0 8

- - - 11 0

AB

C

D

E

D3 = (dij )

3

0 8 13 14 113 0 6 6 12

22 9 0 15 21

7 9 0 0 8

18 20 11 11 0

AB

C

D

E

D4 = (dij )

4

AB

C

D

E

D5 = (dij )

5

to store the path, another matrix can track the last intermediate vertex

0 8 12 12 113 0 6 6 12

22 9 0 15 21

7 9 0 0 8

18 20 11 11 0

Thanks to Wikipedia 2007…Floyd Warshall…

and 2008

How would you change this to find longest paths? What has to be true about the

graph?

by 2009 FW will be a built-in command in Wikipedia pseudocode

New abuse of FW!

Suppose your graph is a list

of edges

def SP( a, b, G ): if a == b: return [ 0.0, b ] if G == []: return [ 1.0e42 ] # infinity

minFromA = SP( a, G[0][0], G[1:] ) minTo_b = SP( G[0][1], b, G[1:] ) totalCost = minFrom_a[0] + minTo_b[0] + G[0][2]

minRest = SP( a, b, G[1:] ) costRest = minRest[0]

if costRest < totalCost: return minRest else: return [ totalCost ] + minFrom_a[1:] + minTo_b[1:]

G = [ ["a", "b", 100], ["a", "c", 300], ["b", "c", 42], ["b", "d", 88], ["c", "d", 1] ];

This week's problems…

Read over these four problems and provide a relative

ranking (and the algorithm you might work with!)

difficulty scale (1 easy - 10 ouch!)

mtwalk

ACM today!

Jotto, continued:

(juniors and sophomores' guesses)

Frosh Sophs Jrs Srs Old people

pluto 0

pluto 2

pluto 3

pluto 1

pluto 1

pluto 0

pluto 2

pluto 3

pluto 1

pluto 1

A look back (at dynamic programming…)

A look forward (graphs!)

IOCCC

See you next Tuesday!

Lab with new problems…

Class Organization

alternating format

discussion sessions

lab sessions

• problem and program analysis

• discussion of strategy and coding tips

• deciding on functional decomposition, data structures, language facilities, and algorithms to use in teams of 2-3

• teams may use 1 machine per person (only the mock contest adheres to ACM rules)

• these problems count for each member of the group

• sometimes new problems, other times with known ones

• ~ 4 problems given out per week…

a team might want to practice with only 1

machine

Class Organization

Feedback from prior semesters…

• make individual vs. team-based work clear, lectures vs. labs

• problems are, in general, individually completed -- except

• there should be an opportunity to start coding “cold”

• snacks and jotto!

• problems per person per week?

• about 1~2 (if you work on a team in lab)

• and consider all of the weeks of the term!

• those done during the lab "mock contest" sessions

• submit for each person (email me if there are problems…)

• provide the code to all team members

• you may or may not choose to work as a team afterwards

Course webpage

references

administrative info

problem statements and sample data

problems you have solved

Grading

CS 189 is graded individually... (it’s possible to take it P/F, too)

Coding Guidelines• problems can be done any time during the semester

• discussion of algorithms always OK

• coding should be within teams

• you may use any references except an existing solution or partial solution…

• one person should take the lead on each problem

• use /cs/ACM/acmSubmit <file> to submit

• try things out !

the reason for ACM!

though not for CS elective credit…

Problem multipliers

Problems are worth double if

• You solve them during the 4:15 - 5:30 lab sessions

• It's one of the "extra difficult" problems, which will be determined as we go…

• The new-language bonus is only in the spring term!

• Any standard language is OK -- but do keep in mind that the competition allows only Java, C, and C++ .

Other "standard" languages:

the team gets credit, up to 3 people

These multipliers may be accumulated…

reasonable alternatives will also be considered…

C#, python, ruby

Language Choice?

Ask about our 2 extra-2-credit projects!

web-updating and web-jotto

Spring 2008 summary

python 82

java 60

C++ 40

Tallies per problem and per language

(thus far)…

17 (+2)

8 4 16 (+2)

1 (+1)

6 (+1)

20 (+12)

(+2)

3 (+1)

1 1 2 11 (+1)

1 (+1)

17 (+9)

(+2)

4 (+2)

1

2 2 8 3 2 8 (+2)

13 (+10)

14 (+9)

1 21 (+16)

(+4)

1 1 15 (+14)

number of 2x scores number

of 4x scores

d 8

ruby 6

scheme 3

lua 2

awk 2

js 2

sqlcobolbasicx86 asmpascalmathematicash, latex

1each

Jotto!

Sophs Jrs Srs Profs

A word-guessing game similar to mastermind…

pluot 1 pluot 0 pluot 1 pluot 2

Dynamic programming!

Dynamic programming

When a seemingly intractable problem has lots of repeated substructure, go DP!

Build a table of partial results.

Replace computation with table look-up when possible

For example:

Dynamic programming



the binary-decimal problem, for example:

263190

Numbers, N, up to 106

Input

0 marks the end of the input

10111011111001

the smallest decimal multiple of N with only

the digits 0 and 1 !

Output

Ideas?

When a seemingly intractable problem has lots of repeated substructure, go DP!

One way…

Count up to the solution, starting from 1…

adding digits changes the error (remainder) in predictable ways

insight: from CS 60!

Dynamic programming

Storing intermediate results in a table for fast look-up:

input N = 6

possible remainders upon dividing by N (6)

# of digits in answer

0 1 2 3 4 5

2

1

3

4

input N = 6



0 1 2 3 4 5

2

1

3

4

1

Dynamic programming


input N = 6



0 1 2 3 4 5

2

1

3

4

1

10 111

Dynamic programming


input N = 6



0 1 2 3 4 5

2

1

3

4

1

111110 10 111

10 111

Dynamic programming


input N = 6



0 1 2 3 4 5

2

1

3

4

1

111110 10 111

10 111

1110 111110 10 111

Dynamic programming


DP!

Only checking values for which a remainder has not yet been used…

Fast

Another example

binary-as-decimal problem

"pebbles" problem (2007 ACM regionals)

Square array, up to 15x15, of integers

from 1 to 99

Input

Output

Idea

place "pebbles" on integers, trying to maximize total, but no two pebbles may be adjacent…

maximum possible sum

14?

3 8 6 7 9 1 4 6 1

vertically, horizontally, or diagonally

3 8 67 9 14 6 1

naïve running time?

Pebbles

3 8 67 9 14 6 1


from 1 to 99

Input

DP Idea consider all possibilities for pebbling each row -they only depend on the previous row's best scores!

Subset chosen (pebbles)

000 001 010 011 100 101 110 111Row #

0

1

2a b c

Store the BEST score available for each possible subset.

3 8 67 9 14 6 1


from 1 to 99

Input



000 001 010 011 100 101 110 111Row #

0

1

2a b c


0 6 8 x 3 9 x x

Pebbles

3 8 67 9 14 6 1


from 1 to 99

Input



000 001 010 011 100 101 110 111Row #

0

1

2a b c


0 6 8 x 3 9 x x

90+9

41+3

99+0

137+6

88+0

x x x

Pebbles

3 8 67 9 14 6 1


from 1 to 99

Input



000 001 010 011 100 101 110 111Row #

0

1

2a b c


0 6 8 x 3 9 x x

90+9

41+3

99+0

137+6

88+0

x x x

x x x0+13 c+13 b+9 a+9 ?

running time?

What is the best here?

Pebbles

binary-as-decimal problem

"pebbles" problem (2007 ACM regionals)

71 24 95 56 5485 50 74 94 2892 96 23 71 1023 61 31 30 4664 33 32 95 89


from 1 to 99

Input

Output

71 24 95 56 5485 50 74 94 2892 96 23 71 1023 61 31 30 4664 33 32 95 89

Idea

place "pebbles" on integers, trying to maximize total, but no two pebbles may be adjacent…

maximum possible sum

572

code

Pebbles

Thanks, Martijn!

Scanner sc = new Scanner(System.in);

even a bit easier!

Martijn is shifty!

Martijn is VERY shifty!

Where is the table?

This sure is sum code…

to the max

Problem Set #0(4 problems)

In teams of 2~3, read over these…

I need a picture of Farmer Ran!


In teams of 2~3, read over these.

• Where does the structure of the problem depend on similar (but smaller!) substructure?

• Think of your next 5-letter jotto word… !

• How might you build up a table of values toward an overall solution?

See you next Tuesday!

bring a laptop, if you have one…

Jotto!

Sophs Jrs Srs Me

A word-guessing game similar to mastermind…

pluot 1

pluot 0

pluot 1

pluot 2

Problem Set #1(6 probs, 3 wks)

Input

4 4 tow cat row care ... .#. ... .## 0 0

# of words in the puzzle (to follow)

# of rows in the puzzle (after the words)

the words

the puzzle

this indicates the end of the input…


Input

4 4 tow cat row care ... .#. ... .## 0 0

either the solution OR a statement that it can't be solved…

Output

Problem 1 cat a#o row e## Problem 2: no layout is possible.


Input

6 5 1

1 2 2 3 4 4 5 1 3 2

1 4 2 1 0 0 0

# of empty boxes on the form

# of clerks in the office (three lines each)

clerk #0


the box(es) CHECKED

the box(es) ERASED the clerks who get a copy

clerk #1

clerk #2

clerk #3

clerk #4

0 1 2 3 4 5

the form


Input

6 5 1

1 2 2 3 4 4 5 1 3 2

1 4 2 1 0 0 0



clerk #0


the box(es) CHECKED


clerk #1

clerk #2

clerk #3

clerk #4

0 1 2 3 4 5

the form

let's try it…


Input

6 5 1

1 2 2 3 4 4 5 1 3 2

1 4 2 1 0 0 0



clerk #0


the box(es) CHECKED


clerk #1

clerk #2

clerk #3

clerk #4

0 1 2 3 4 5

the form

Output1 3 4 5

the boxes checked the last time it leaves clerk #0's

desk…


Input

RDDR Speedy M 0101 Jumper F 0101 Slowpoke M 1101 Terror F 1100 Shadow F 1001 *** Frisky 0101 Sleepy 1101***

list of traits, R == "recessive" D == "dominant"

D traits are passed if EITHER parent has themR traits are passed if BOTH parents have them

all of the parents, gender, and traits

the baby shrews…

Deduce their possible parents!


Input





the baby bunnies…


Output

Frisky by Jumper-Slowpoke or Jumper-Speedy or ______Sleepy by _________


Input





the baby bunnies…


Output

Frisky by Jumper-Slowpoke or Jumper-Speedyor Shadow-SpeedySleepy by Shadow-Slowpoke


Decide which problem is the easiest and which one is the hardest …

(to code, not to compute!)

Read these three problems… then


my estimates…

hardest

easiest

important heuristic:I’m always wrong

See you next Tuesday

in the CS labs… !

Welcome to Programming Practicum“Putting the C

into CS”

You aren’t here

writing clinic reports

clinic liaison phone call

coding chunky strings

rebooting knuth (or turing or…)

installing

Debian 3.1

Engineering dept.

the dumpster

University of St. Petersburg

On the 405, in traffic, being chased by police (and TV) helicopters.

Mailing something at the Claremont Post Office

Waiting for the snow enveloping you on Route 5 N to melt

Krispy Kreme’s drive through

Teaching Honors English for Janice Barbee at

Pomona High School

Worldcom Headquarters

Leading a Gray Davis / Gary Coleman / Arnold “T-800” Schwarzenegger gubernatorial fundraiser

exploring martian soil

Being dragged off-course 18 miles into a marathon race by a crazed spectator

Massey University Palmerston North, NZ

Pittsburgh

Driving N on the Dalton Highway… (though it feels like it!)

What is this course about?

• A chance to “improve” your programming skillsAlgorithm analysis and

insightProgram design and implementation

optimizing coding time

ACM programming contest

What

Why

Research/prototype programming

Hands-on practice with algorithms and techniques

Unofficial course name: CS -70

Familiarity with Java’s libraries OR your choice of language

Course Organization

Jan 16 Welcome! Random teams of 3: 6 problems, 3 weeks

Jan 23 Lab session to work on problems (Beckman B102 or 105)

Jan 30 Discussion session on the first set of problems Feb 6 Lab session with new problems: 4 problems, 2 weeks

Feb 13 Discussion session on the second set of problemsFeb 20 Lab session with new problems: 6 problems, 3 weeks

Feb 27 Discussion session on the third set of problems

Mar 6 No class - Fall breakMar 20 Mock ACM contest, 9pm – 1am, teams of 3, 6 pr, 4 hours

Mar 27 No class (out of town)

Apr 3 Discussion session on the mock contest + Finale!

You may submit problems until the end of exams…

2 per team

2/team

3 per team

1-4 / team

Class Organization

alternating format

discussion sessions

lab sessions




• teams should use 1 terminal per person (only the mock contest adheres to ACM rules)

• these problems count for each member of the group• sometimes new problems, other times with known ones

• ~1 problem per week per person…

Course webpage

reference links

administrative info

problem statements and test data

problems your team has solved

Grading


Coding Guidelines• problems can be done any time

during the semester







the reason for ACM!

Choose your language…

• extensive library of data structures and algorithms available

Java is almost the universal choice for the competition…

• I/O made simpler with 1.5’s Scanner and printf

the C in CS!

Input from stdin

Output to stdout


Python is nice

C#

Whatever language you choose needs to be able to run on the Macs in

the CS labs (and preferably knuth, as

well…)

I’ll likely need your help to get things set

up for testing…

def floyd_warshall(W, infinity): n = matrix.get_num_rows(W) D = matrix.clone(W) DD = matrix.make(n,n) for k in xrange(n): for i in xrange(n): for j in xrange(n): DD[i][j] = min(D[i][j], D[i][k] + D[k][j]) DD, D = D, DD return D

Others ?Marty: prolog!


Input

4 4 tow cat row care ... .#. ... .## 0 0

# of words in the puzzle (to follow)

# of rows in the puzzle (after the words)

the words

the puzzle



Input

6 5 1

1 2 2 3 4 4 5 1 3 2

1 4 2 1 0 0 0



clerk #0


the box(es) CHECKED


clerk #1

clerk #2

clerk #3

clerk #4

0 1 2 3 4 5

the form

Output1 3 4 5

the boxes checked the last time it leaves clerk #0's

desk…


Input





the baby shrews…


Output

Frisky by Jumper-Slowpoke or Jumper-Speedy or ______Sleepy by _________


Decide which problem is the easiest and which one is the hardest …

(to code, not to compute!)

Read these three problems… then

Coaches’ Room


• extensive library of data structures and algorithms available

Java/Cthe universal choice for the competition…

• I/O made simpler with 1.5’s Scanner and printf

the C in CS!

Input from stdin

Output to stdout


Python is nice

def floyd_warshall(W, infinity): n = matrix.get_num_rows(W) D = matrix.clone(W) DD = matrix.make(n,n) for k in xrange(n): for i in xrange(n): for j in xrange(n): DD[i][j] = min(D[i][j], D[i][k] + D[k][j]) DD, D = D, DD return D

Ruby :-)

Marty: prolog!

Postscript!

Welcome to Programming Practicum“Putting the C

into CS”

You aren’t here

writing clinic reports

clinic liaison phone call

coding chunky strings

rebooting knuth (or turing or…)

installing

Debian 3.1

Engineering dept.

the dumpster

University of St. Petersburg

On the 405, in traffic, being chased by police (and TV) helicopters.

Mailing something at the Claremont Post Office

Waiting for the snow enveloping you on Route 5 N to melt

Krispy Kreme’s drive-through

Teaching Honors English for Janice Barbee at

Pomona High School

Worldcom Headquarters

Leading a Gray Davis / Gary Coleman / Arnold “T-800” Schwarzenegger gubernatorial fundraiser

exploring martian soil

Being dragged off-course 18 miles into a marathon race by a crazed spectator

Massey University Palmerston North, NZ

Pittsburgh

Driving N on the Dalton Highway… (though it feels like it!)

Victorville, for DARPA's Urban Granc Challenge

Waiting in line to vote in the Florida primaries…

Waiting in line to vote in the Florida primaries…

What is this course about?

• A chance to “improve” your programming skillsAlgorithm analysis and

insightProgram design and implementation

optimizing coding time

ACM programming contest

What

Why

Research/prototype programming

Hands-on practice with algorithms and techniques

Unofficial course name: CS -70

Familiarity with Java’s libraries OR your choice of language

Class Organization

alternating format

discussion sessions

lab sessions




• teams should use 1 machine per person (only the mock contest adheres to ACM rules)

• these problems count for each member of the group• sometimes new problems, other times with known ones

• ~3 problems per week per person…

Class Organization

Feedback from prior semesters…

• make individual vs. team-based work clear, lectures vs. labs

• problems are, in general, individually completed, except

• there should be an opportunity to start coding “cold”

• snacks and jotto!

• problems per person per week?

• ~2 in the fall

• ~3 in the spring

• those done during the lab "mock contest" sessions

• submit for each person (or email me…)

• provide the code to all team members

• you may or may not choose to work as a team afterwards

Course Organization

Jan 29 Welcome! Review of dynamic programming: 4 problemsFeb 5 Lab/Mock contest session: 4 problems

Feb 12 Discussion session on geometry problems: 4 problemsFeb 19 Lab/Mock contest session: 4 problems

Feb 26 Lab/Mock contest session: 4 problems

Mar 4 Discussion session on search problems: 4 problems

Mar 11 No class… need to be away

Mar 18 No class - Spring breakMar 23 Mock ACM contest, 9pm – midnight, 6 problems

Mar 25 Discussion and wrap-up of the semester

You may submit problems until the

end of exams…

Sat. Mar 8 and Sat. Apr 19external

competitions…

Competition Options

www.ccsc.org/southwestern/2008/contest.html

www.ieee.org/web/membership/students/scholarshipsawardscontests/ieeextreme.html


competitions…

Course webpage

references

administrative info

problem statements and test data

problems you have solved

Grading


Coding Guidelines• problems can be done any time

during the semester







the reason for ACM!

Problem multipliers

Problems are worth double if

• You solve them during the 4:15 - 5:30 lab sessions

• You are the first person to use a particular language - though there is an additional responsibility here: to set up the testing system to handle that language!

• It's one of the "extra difficult" problems, which will be determined as we go…

languages already used:

the team gets credit, up to 3 people

python 56

ruby 12

java 6

c++ 11

perl 2

postscript 2

c# 8

haskell 1

prolog 2

c 5

php 1

These multipliers may be accumulated…

Dynamic programming

When a seemingly intractable problem has large amounts of repeated or redundant substructure, DP can sometimes provide an efficient solution.



For example:

263190

Numbers, N, up to 106

Input

0 marks the end of the input

10111011111001

the smallest decimal multiple of N with only

the digits 0 and 1 !

Output

Ideas?

One way…

Count up to the solution, starting from 1…

Dynamic programming

Storing intermediate results in a table for fast look-up:input N = 6



0 1 2 3 4 5

2

1

3

4

1

111110 10 111

10 111

1110 111110 10 111

DP!

Only checking values for which a remainder has not yet been used…


In teams of ~3, think about

- how would you solve this problem?

- how could you most simplify the programming ?- think of a 5-letter jotto word… !

- is it a dynamic programming problem?

- divide up with one problem per group -

Competition Options

www.ccsc.org/southwestern/2008/contest.html

www.ieee.org/web/membership/students/scholarshipsawardscontests/ieeextreme.html


competitions…

acm today some nice unix commands… practice problems? code.google.com/codejam/ this week: beyond...

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