Welcome to

Computer Programming Contest

Orientation

Presented by

Ahmed Shamsul Arefin

The University of Newcastle, Australia

Ahmed.Arefin@newcastle.edu.au

11/6/2011 1

Based on a Programming Contest Training Workshop by Shahriar Manzoor (Judge, WF Contest) and

Rezaul Alam Chowdhury (Faculty, State University of New York at Stony Brook).

Part One

General Information

Conduct of the Contest

Computing Environment

Judgment

Scoring

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Recap -

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University of New South Wales

Team name: 13337 ViSu4L B451c PWN3RZ!11!

Team

Kitten Tofu

Jarrah Lacko

Christopher Chen

Coach Tim Lambert

ACM South Pacific Regional

Contest Results 2011

Recap- Regional Top 10

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Place Team University Solutions Time

1 13337 ViSu4L B451c PWN3RZ!11! University of New South Wales 10 1025

2 Brogrammers University of Sydney 8 1320

3 DatJoCur Queensland University of Technology 6 943

4 Pre-Raphaelite Shaolin University of New South Wales 5 414

5 Funrolled Loops University of Canterbury 5 423

6 DJ Tomato Victoria University of Wellington 5 458

7 INT_MIN / -1 (red) University of Auckland 5 486

8 lg(k) University of New South Wales 5 665

9 Special Tactics University of Western Australia 5 885

10 UTas A University of Tasmania 4 227

http://www.sppcontest.org/2011/SP_Results_2011.html#Australia

Bigger Picture (World Final)

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Year Institution Country

2011 Zhejiang University China

2010 Shanghai Jiao Tong University China

2009Saint Petersburg State University of Information

Technologies, Mechanics and OpticsRussia

2008Saint Petersburg State University of Information

Technologies, Mechanics and OpticsRussia

2007 University of Warsaw Poland

2006 Saratov State University Russia

2005 Shanghai Jiao Tong University China

2004Saint Petersburg State University of Information

Technologies, Mechanics and OpticsRussia

2003 University of Warsaw Poland

2002 Shanghai Jiao Tong University China

2001 St. Petersburg State University Russia

2000 St. Petersburg State University Russia

1999 University of Waterloo Canada

1998 Charles University Czech Republic

1997 Harvey Mudd College United States

1996 University of California, Berkeley United States

1995 Albert-Ludwigs-Universität Freiburg, Germany

1994 University of Waterloo Canada

1993 Harvard University United States

1992 University of Melbourne Australia

1991 Stanford University United States

1990 University of Otago New Zealand

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6

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Recap- Contest Environment

11/6/2011 6Picture Source : Internet/ Google Uncle!

Conduct of the Contest

• Exactly eight (8) to ten(10) programming

problems will be posed in English.

• Only one (1) computer is allocated for each

team.

• The contest will run for five (5) hours.

• Teams will try to write the solutions of the

problems in any one of the programming

languages allowed (C/C++,Java) and submit

for acceptance.

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Conduct of the Contest

Resource materials such as books,

manuals, and printed program listings.

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Allowed:

Machine readable versions of programs

or data.

Calculators, laptop/palmtop computers.

Mobile phones and other communication

devices.

Prohibited:

Conduct of the Contest

Conversation (during contest hours) with

anyone (including the coach) except

members of own team and system

support staffs.

Any activity that jeopardizes the contest.

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Prohibited:

Conduct of the Contest (del)

• The Chairman of the Program Committee has the authority to change the duration of the contest in the event of unforeseen difficulties.

• In case of interruption of power for duration of less than 30 minutes, contest will continue for at least half an hour after the restoration of power (Not Applicable in AUSTRALIA).

• In any case the exact timing will be decided according to the situation.

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Contest Duration:

Computing Environment

One team, one computer.

All the computers run on same operating system (Windows or Linux).

All computers are networked together.

Programming languages allowed are : C, C++ and Java.

Convenient development tools will be provided for each of the languages.

Solutions must be submitted to the judgesthrough network using the PC2 judging utility.

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Judgement

• If you are confident about your solution to a problem, submit it for judgement.

• Each of your submitted runs is judged as accepted or rejected, and you will be

notified of the results with full-screen messages.

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Judgement

Will be notified as Correct.

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Accepted Solutions:

Incorrect Output.

No Output.

Presentation Error.

Run Time Error.

Time Limit Exceeded.

Rejected Solutions:

Judgement

• Your solution must read input from a filespecified in the program description and produce output to the standard output.

• But when the judges test your program that input file contains some additional secret data specially designed to check the correctness of a solution.

• If the output of your program matches with what the judges expected, your solution is considered Correct.

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Correct:

Judgement

• If the output of your program does not

match with what the judges expect, you

will get an Incorrect Output notification.

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Incorrect Output:

Judgement

• Your program runs but does not produce any output for the judges’ secret input data.

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No Output:

Some Possible Causes:

The name or the path of the input file in

your program may be written incorrectly.

The input file will always be in the current

directory.

Assuming incorrect input data format.

Run time error.

Judgement

• Possibly your solution produces correct

output for the judges’ secret data, but

does not print it in the proper format.

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Presentation Error:

Some Possible Causes:

White-space and newline characters in

improper numbers and positions.

Spelling mistake.

Case mismatch.

Judgement

• Your program performs an illegal operationwhen run on the judges’ input.

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Run Time Error:

Some Illegal Operations:

Invalid memory access.

Divide by zero.

Overflow.

Domain error.

Judgement

• The judges allow your program to produce

output for their secret data within a specific

time period. If your program fails to do so,

you get a TLE notification.

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Time Limit Exceeded:

Some Possible Causes:

Using an inefficient algorithm.

Infinite loop.

Waiting for input from standard input

device.

Assuming wrong input data format.

Scoring

• Teams are ranked according to the most

problems solved (judged Correct).

• Teams who solve the same number of

problems are ranked by least total penalty

time.

• Teams who are still tied are ranked by the

earliest time of submittal of the last

accepted problem.

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Scoring

• Say a team has submitted the correct solution of a problem at the 120th minute, but made 3 rejected submissions before the correct one. So, penalty = 120 + 20 3 = 180 minutes.

• Now, if they submit the correct solution of another problem at the 300th minute with 4 rejected submissions before the correct one, then total penalty = (300 + 20 4) + 180 = 380 + 180 = 560 minutes.

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Sample Calculation:

(This figure is illustrative, i.e., based on a different penalty value)

Part Two

Tips on Team Strategy

Frequently Set Problems

Efficient Programming

Team Strategy

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A Good Programming Team

• Must have knowledge of standard algorithms and the ability to find an appropriate algorithm for every problem in the set.

• Ability to code an algorithm into a working program.

• A strategy of co-operation with teammates.

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Frequently Set Problems

Search Problems

Graph Problems

Geometric Problems

Dynamic Programming Problems

Trivial Problems

Non-standard Problems

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Efficient Programming

Type as fast as you can.

Subsequently spend a lot of time debugging.

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Does not mean:

Instead:

Think carefully about the problem and all

the cases which might occur.

Then program your algorithm, and take

the time to ensure that you get it right the

first time with a minimum amount of

debugging.

To Become a Team

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Play a lot of training contests under

circumstances which are as close to the

real contest as possible.

Practice! Practice!! Practice!!!

http://uva.onlinejudge.org/

Tips on Team Strategy

Analyze the problem set first.

Try to divide the problems into difficulty

classes: easy, medium, hard, etc.

Try to solve the easy problems first.

Be careful not to misjudge the difficulty of

a problem.

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Tips on Team Strategy

Every member need not know all arts of programming but everyone must have the basic skills of programming such as writing procedures, debugging, compiling.

Then some may be specialized for searching, graph traversing problems, some other dynamic programming and one should have deep knowledge of mathematics, etc.

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Tips on Team Strategy

Every team member should know every other

member’s weakness and strength so when he

reads a problem he should understand who is

The MAN to solve that problem.

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Tips on Team Strategy

Don’t waste much of your time with a

single problem. Your team mate may find a

good solution quickly for that.

Try to read all problems.

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Tips on Team Strategy

The team members should have good understanding between them because they will have to decide when one will leave the computer.

Always think about the welfare of the team. Contest is not a time to become selfish. You should not think like “Oh, I have finished my quota” or “I must solve one problem any how” or “I will be dropped next time.”

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Tips on Team Strategy

The most efficient way to write a program is to write it alone. Thus you avoid communication overhead and the confusion caused by differing programming style.

Solving problems together can also be helpful. This strategy works out when the question is hard. This is also good for the team whose aim is to solve at least one problem.

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Tips on Team Strategy

In a 5 hour contest you have 15 man hours

and only 5 computer hours. So computer

time is extremely valuable. It will be a great

pity if all three man are busy with solving

problems and the computer is left lonely.

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Tips on Team Strategy

If the easiest problem of the contest is getting

rejected for some silly mistakes then it is often

a good idea to redo the problem (by some

other member of the team).

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Tips on Team Strategy

Try to see the current standing and also

find out which problem is solved most. If

that problem is not solved by your team

then try to solve it immediately.

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Tips on Team Strategy

Use the chair in front of the computer only for typing and not for thinking. Write your program on the paper, analyze it and then go in front of the computer.

When your solution gets rejected by the judges try to think about your mistakes rather than debugging on the computer. REAL TIME DEBUGGING is the ultimate Sin.

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Final Words on Strategy

The Scoring system of a Contest is digital. So you don’t get any point for a 99 % solved problem. That is why, don’t try to attack too many problems. At the end of the contest you may find that you have solved all problems 90% and your team is at the bottom of the rank list.

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Sample Problem

I Love Big Numbers !• The Problem

• A Japanese young girl went to a Science Fair at Tokyo. There she met with a Robot named Mico-12, which had AI (You must know about AI-Artificial Intelligence). The Japanese girl thought, she can do some fun with that Robot. She asked her, "Do you have any idea about maths ?"."Yes! I love mathematics", The Robot replied.

• "Okey ! Then I am giving you a number, you have to find out the Factorial of that number. Then find the sum of the digits of your result!. Suppose the number is 5.You first calculate 5!=120, then find sum of the digits 1+2+0=3.Can you do it?"

• "Yes. I can do!"Robot replied.

• "Suppose the number is 100, what will be the result ?".At this point the Robot started thinking and calculating. After a few minutes the Robot head burned out and it cried out loudly "Time Limit Exceeds".

• The girl laughed at the Robot and said "The sum is definitely 648".

• "How can you tell that ?" Robot asked the girl. "Because I am an ACM World Finalist and I can solve the Big Number problems easily." Saying this, the girl closed her laptop computer and went away.

• Now, your task is to help the Robot with the similar problem.

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I Love Big Numbers !

• The Input

• The input file will contain one or more test cases.

• Each test case consists of one line containing an integers n (n<=1000).

• The Output

• For each test case, print one line containing the required number. This number will always fit into an integer, i.e. it will be less than 2^31-1.

• Sample Input

• 5

• 60

• 100

• Sample Output

• 3

• 288

• 648

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Set by Ahmed Shamsul Arefin (2001- RockFord Programming Contest)

http://uva.onlinejudge.org/ http://acm.uva.es/39

Thanks • External links (From Wikipedia)

• Official website

• Official Website of the ACM-ICPC - maintained at Baylor University.

• ICPC Blogs

• ACMSolver - maintained by Ahmed Shamsul Arefin (That’s me!)

• Igor's UVa - maintained by Igor Naverniouk

• Andrian Kurniady's ICPC event blog - maintained by Andrian Kurniady

• Codeforces blogs

• ICPC Training

• Algorithmist - maintained by Algorithmist Team

• Steven Halim's Method to solve ACM UVa OJ Problems - maintained by Steven

Halim

• The Stony Brook Algorithm Repository - maintained by Steven Skiena.

• Programming Challenges - maintained by Miguel Revilla

• Light Online Judge - maintained by Jane Alam Jan

• UVa Online Judge Board - maintained by Universidad de Valladolid Online Judge

• Caribbean training platform - maintained by Xtreme Team

• CodeChef - maintained by Directi Group

• Hello-World - maintained by Sang Song

Original Slides by: Shahriar Manzoor (Judge, WF Contest) and Rezaul Alam

Chowdhury (Faculty, State University of New York at Stony Brook).40