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.
- Find three numbers such that x=y and y=z, but
x≠z. Impossible, right?
- Sometimes, you don't have to program, you can just play a game.
Though that might be harder than it looks...
- 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?
- 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
(2011/H, 2011/I, 2009/I, 2007/Q, 2005/Q, 2004/G)
If that sounds interesting, you should compete in
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 2015 will start on
20 June 2015 at 11:00 UTC, so get ready!
Find a team of up to 3 people, or compete as an individual.
Read the contest rules and
register for the contest.
Registration will start on or before
11 May 2015.
Optionally, take part in the
to see how the contest works – especially if you're competing for the
When the contest starts, read the
and begin solving.
Choose a problem, download its input files, and try to write a program that
produces the correct output file.
Submit the output file
and wait until it's judged "OK" or "Wrong answer".
Repeat that until you have solved everything.
IPSC 2015 is coming
IPSC 2015 will take place
from 20 June 2015, 11:00 UTC
to 20 June 2015, 16:00 UTC.
(Click the links to find out your local time.)
The practice session runs
from 19 June 2015, 9:00 UTC
to 20 June 2015, 9:00 UTC.
If you want to prepare for the contest, try our new
Training Area, where you can practice on all past IPSC
contests since it began in 1999.
Good luck and have fun!
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 2015 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,