# Internet Problem Solving Contest

## Welcome to IPSC

The Internet Problem Solving Contest is an online programming competition for teams of up to three people. Each year, hundreds of teams gather to solve challenging problems and test their skills against some of the best programmers in the world.

The problems range from easy to very hard, so everyone is welcome to compete. We also have separate ranklists for individuals and secondary school students. You can use any programming language, or even solve problems by hand. Most of the problems are algorithmic in nature, but IPSC is particularly known for its unusual and fun problems. Here are some of our favorites:

• In one task, your goal is not to sort the input sequence. (2010/A)
• Find three numbers such that x=y and y=z, but x≠z. Impossible, right? (2008/C)
• Sometimes, you don't have to program, you can just play a game. Though that might be harder than it looks... (2013/L, 2009/F)
• The input files don't have to be lists of numbers. How about images or even music? (2013/I, 2012/J, 2009/C, 2008/H, 2007/E)
• Some problems require multiple attempts, because each one gives you new information. (2013/F, 2012/K, 2010/E, 2004/D)
• No one likes ambiguous problem statements, but what about a problem that doesn't have any problem statement? (2012/B, 2011/Q)
• Some tasks are about analyzing obfuscated pieces of code or oddly encoded data. (2013/C, 2006/M, 2003/B)
• Don't be surprised if a task has its own scoring rules. In 2009/D, every wrong answer counts as a bonus instead of a penalty. In 2010/M, your score depends on how well you predict the actions of other teams. And in 2011/M, you just have to take care of a little puppy.
• Multiple problems involve using various esoteric programming languages. (2011/H, 2011/I, 2009/I, 2007/Q, 2005/Q, 2004/G)

If that sounds interesting, you should compete in IPSC 2016! Until then, you can also try solving the above problems in the Training Area. Or browse through our Archive and see if anything else catches your eye.

### How to compete

IPSC 2016 will start on 18 June 2016 at 11:00 UTC, so get ready!

1. Find a team of up to 3 people, or compete as an individual.
2. Read the contest rules and register for the contest. Registration will start on or before 11 May 2016.
3. Optionally, take part in the practice session to see how the contest works – especially if you're competing for the first time.
4. When the contest starts, read the problem statements and begin solving.
5. Choose a problem, download its input files, and try to write a program that produces the correct output file.
6. Submit the output file and wait until it's judged "OK" or "Wrong answer".
7. Repeat that until you have solved everything.

### IPSC 2016 is coming

IPSC 2016 will take place from 18 June 2016, 11:00 UTC to 18 June 2016, 16:00 UTC. (Click the links to find out your local time.)
The practice session runs from 17 June 2016, 9:00 UTC to 18 June 2016, 9:00 UTC.

If you want to prepare for the contest, visit our Training Area, where you can practice on all past IPSC contests since it began in 1999.

Good luck and have fun!

### Postcard Quest

We still don't have enough postcards from all over the world. Therefore the annual special task remains: You are encouraged to send us a nice postcard. If the postcard arrives before IPSC 2016 begins, your team will be awarded -60 penalty minutes. (Don't forget to write the name of your team on the back of the postcard.)

Our address: KSP, KZVI FMFI UK, Mlynska dolina, 842 48 Bratislava, Slovakia.