This is the list of problems from all past IPSC contests.
Please note that all IPSC problems are licensed under the CC BYSA 3.0 license.
IPSC 2018  Input data packages, Problems and solutions booklet 

Armed bandit 
Find any output + the lex. min. output of a slot machine.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Brain fold 
Fold paper many times, cut it once, count pieces.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Counting rectangles 
Count sets of n rectangles that differ after coordinate compression.

Delightful 
Write programs in ternary assembler.

Encrypted romance 
Count sparse collisions for a collection of hash functions.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Farmer's code 
Decipher the way apple tree crossing works.
Input files:
Dashboard.

Git gud 
List all files in a git repository.

Hats of various colors 
Write programs that play a hat puzzle in parallel.
Input files:
Helper program for testing.

Incorrect expression 
Find all possible values after one character is changed in an expression.
Input files:
Easy input data set – I1,
Hard input data set – I2.

Jumping over walls 
Construct the smallest maze in which you need to use all directions of jumps.

Kids draw the darndest things 
Compute exact values of a weird continuous function.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Lethargic foe 
Quickly win games of symmetric chess.

McDroid's 
Run a restaurant for robots.
Input files:
Dashboard.

IPSC 2018 practice session  
Partitioning a square 
Find the smallest square that can be divided into n equal regions.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Qizz Quzz 
Check validity of generalized Fizz Buzz sequences.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.

Raw data 
Make a POST request to our webserver.

IPSC 2017  Input data packages, Problems and solutions booklet 
Automated flooding 
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bishopian paths 
Input files:
Easy input data set – B1,
Hard input data set – B2.

Collector's dilemma 
Input files:
Easy input data set – C1,
Hard input data set – C2.

Dazzling digits 
Input files:
Easy input data set – D1,
Hard input data set – D2.

Elevation alteration 
Input files:
Easy input data set – E1,
Hard input data set – E2 (generator).

Flipping and cutting 
Input files:
Easy input data set – F1,
Hard input data set – F2.

Gunfight  
Holy cow, Vim!  
Internet problem 
Input files:
Easy input data set – I1,
Hard input data set – I2.

Judicious cuts 
Input files:
Easy input data set – J1,
Hard input data set – J2.

Kirk or Picard? 
Input files:
Input data set – K.

Lucky draws  
Matching pairs 
Input files:
Input data set – M.

IPSC 2017 practice session  
Queue skipping 
Input files:
Easy input data set – Q1,
Hard input data set – Q2 (generator).

Russian roulette 
Input files:
Easy input data set – R1,
Hard input data set – R2.

St. Ives 
Input files:
Easy input data set – S1,
Hard input data set – S2.

IPSC 2016  Input data packages, Problems and solutions booklet 
Avoiding accidents 
Overlap and concatenate a few strings.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bounding box 
Place a given set of balls into a 3D box.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Counting swaps 
Count the ways of sorting a sequence using fewest swaps.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Dumb clicking 
Win a simple browserbased clicking game.
Input files:
Easy game – D1,
Hard game – D2.

Evil minesweeper 
Write an evil backend for a minesweeper game.
Input files:
Easy input data set – E1,
Hard input data set – E2.
Solutions:
Solution,
Booklet,
One possible correct output for E1,
One possible correct output for E2,
C++ program that precomputes solutions of small instances,
C++ header file with precomputed solutions of small instances,
C++ program solving both subproblems,
Python 3 program to check submissions.

Ferries 
Get an object from position x to position y using given permutations.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Greatest number 
Remove symbols from a simple expression to maximize its value.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Heavy snowfall 
Simulate snowfall and snow plowing on a tree.

Intelligence report 
Recover passwords from images.
Input files:
Easy input data set – I1,
Hard input data set – I2.

Jumping queues 
Choose the best checkout line in a fairly complicated setting.

Kill switch 
Given a 'sorting' algorithm, find the shortest input it does not sort.

Luxor Catchya! 
Solve a captcha that uses hieroglyphics.
Input files:
A zip file with test data for both L1 and L2.

Mana troubles 
Tap Magic the Gathering lands for mana.

IPSC 2016 practice session  
Subsequence 
Check whether one string is a subsequence of another.
Input files:
Easy input data set – S1,
Hard input data set – S2 (generator).

Turning gears 
Given a machine with many linked gears, how will they rotate?
Input files:
Easy input data set – T1,
Hard input data set – T2.

Ultimate magic rectangles 
Compute the number of generalized magic squares.
Input files:
Easy input data set – U1,
Hard input data set – U2.

IPSC 2015  Input data packages, Problems and solutions booklet 
A+B 
Build the largest sum A+B from given digits.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bawdy Boilbrained Bugbear 
Build a threeword insult with the given strength.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Chess Pieces 
Play a game of chess and create many identical pieces.

Dijkstra's Nightmare 
Show that Dijkstra's algorithm can be exponential when negative edges are allowed.

Enclosure 
Catch the cat!

Familiar Couples 
Disjoint set union "in two dimensions".
Input files:
Easy input data set – F1,
Hard input data set – F2 (generator).

Generating Synergy 
Coloring a rooted tree up to a given depth.
Input files:
Easy input data set – G1,
Hard input data set – G2 (generator).

Humble Captains 
Dividing kids into teams and optimizing stuff about pairs of friends.
Input files:
Easy input data set – H1,
Hard input data set – H2.

Inexpensive Travel 
Find all shortest paths for cyclists with various distance/ascent preferences.
Input files:
Easy input data set – I1,
Hard input data set – I2 (generator).

Juicy Dot Coms 
Crack an old 16bit .COM file.
Input files:
File for subproblem J1,
File for subproblem J2.

Klingelt das Glockenspiel 
Listen to bells on a wall and determine their locations.
Input files:
File for subproblem K1,
File for subproblem K2.

Lunchtime! 
Make sense of a foreignlanguage menu by ordering food in a smart way.
Input files:
Easy input data set – L1,
Hard input data set – L2.

Make*mean+[integer!] 
Write programs in a restricted subset of JavaScript.

IPSC 2015 practice session  
Solitaire 
Compute the number of rounds of a simple game of solitaire.
Input files:
Easy input data set – S1,
Hard input data set – S2 (generator).

Town 
Given a box of digits, number as many houses as you can.
Input files:
Easy input data set – T1,
Hard input data set – T2.

Unusual Game Show 
Monty Hall problem with a twist.
Input files:
Easy input data set – U1,
Hard input data set – U2.

IPSC 2014  Input data packages, Problems and solutions booklet 
Adjusting passwords 
Check whether using backspace pays off.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Beating the game 
Play a onedimensional version of the game 2048.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Copier 
Reverse an operation that copies a part of a string.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Disk space eater 
Unzip one exabyte of zeros.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Empathy system 
Recognize four different emotions in photos.
Input files:
Input data set – E.

Find a sudoku in π 
Find nine matching rows of a sudoku in π.

Game on a conveyor belt 
Play a surprisingly complicated game of NIM on a conveyor belt.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Hashsets 
Find hard inputs for standard hashsets in C++ and Java.
Input files:
C++ program – h.cc,
Java program – h.java.

Intrepid cave explorer 
Label all vertices of a tree optimally.
Input files:
Easy input data set – I1,
Hard input data set – I2.

Judging programs 
Discover which programs do solve a given problem and which ones don't.
Input files:
Easy input data set – J1,
Easy input data set – J2.

Knowledge test 
Solve a crossword.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Let there be sound 
Decode a sound file... and more.
Input files:
Easy input data set – L1,
Easy input data set – L2.

Maximum enjoyment 
Solve a maximum flow problem with a path length limit.
Input files:
Easy input data set – M1,
Hard input data set – M2.

IPSC 2014 practice session  
Say it loudly! 
Find the *LOUDEST* sentence.
Input files:
Easy input data set – S1,
Hard input data set – S2.

Two covers 
Which parts of a sequence are covered twice?
Input files:
Easy input data set – T1,
Hard input data set – T2.

Urban planning 
Find the smallest road network with the same transitive closure.
Input files:
Easy input data set – U1,
Hard input data set – U2.

IPSC 2013  Input data packages, Problems and solutions booklet 
Advice for Olivia 
Pay a sum using sufficiently few coins and banknotes.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Boredom buster 
Find the best way of breaking a number into ones.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Code Inception 
Analyze programs that output instructions how to modify them.

Do the grading 
Write a grader for the practice task R.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Exploring the cave 
Find a NFA with n states such that the corresponding DFA has d states.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Feeling lucky? 
Play a weighing game that involves randomness.
Solutions:
Booklet.

Grid travel 
Find the longest path from A to B on a rectangular grid.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Histiaeus 
Locate a hidden message carried by a slave.

Invisible cats 
Descramble a collection of images and find all cats.

Just a single gate 
Find all universal ternary gates.

Knee problems 
Count the ways of walking up and down the stairs.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Labyrinth 
Find your way through a seemingly simple labyrinth with buttons.
Input files:
JavaScript game – L1, L2.

Morning hassle 
Find the fastest way to drive your car over railroad crossings.
Input files:
Easy input data set – M1,
Hard input data set – M2.

IPSC 2013 practice session  
Plus one 
Increment the given number by 1... with a twist!
Input files:
Easy input data set – P1,
Hard input data set – P2.

Quite the cheater! 
Find a sequence with a given mean and a given variance.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.

Rearranged alphabet 
Find a short string that contains each permutation as a subsequence.

IPSC 2012  Input data packages, Problems and solutions booklet 
Abundance of sweets 
Look for all candies in a matrix of characters.
Input files:
Easy input data set – A1,
Hard input data set – A2.

(blank) 
Solve a task with no problem statement, using just the messages from the grader.
Solutions:
Booklet,
Python program for the last step of solving B1.

Card game 
Find the best strategy in a card game involving probability.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Data mania 
Answer queries about data from past years of IPSC.

Evil matching 
Solve a pattern matching problem in which we can add adjacent elements of text.

Fair coin toss 
Try to simulate a fair coin by xoring biased ones.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Gems in the maze 
Find the longest path in a graph with outdegree 1.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Harvesting potatoes 
Plan the optimal schedule for a harvester.
Input files:
Easy input data set – H1,
Hard input data set – H2.

Invert the youknowwhat 
Recover a password from a related MD5 hash.
Input files:
Password file for both data sets – I1, I2.
Solutions:
Booklet,
Decrypted passwords.

Jukebox 
Convert a recording of a simple song into musical notes.

Keys and locks 
Determine the master key for a pin tumbler lock.

Light in a room 
Compute the area lit by a cone of light in a room.
Input files:
Easy input data set – L1,
Hard input data set – L2.

Matrix nightmare 
Given a polynomial, find a matrix such that its determinant is the given polynomial.
Input files:
Easy input data set – M1,
Hard input data set – M2.

IPSC 2012 practice session  
Partitioning containers 
Split numbers with sum S into two subsets of size at most S/2 and possibly one extra element.
Input files:
Easy input data set – P1,
Hard input data set – P2.
Solutions:
Booklet.

Quaint encryption 
Find one alphabet permutation consistent with a given substitution cipher.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.
Solutions:
Booklet.

Rebel Alliance attacks 
In a sphere, find all grid points with integer distance to the center.
Input files:
Easy input data set – R1,
Hard input data set – R2.
Solutions:
Booklet.

IPSC 2011  Input data packages, Problems and solutions booklet 
Against a rock play Spock 
Always win in a RockPaperScissorsLizardSpock game.
Input files:
Easy input data set – A1,
Hard input data set – A2.
Solutions:
Booklet,
Program solving both data sets.

BFS killer 
Find a maze for which BFS needs a long queue.
Input files:
Easy input data set – B1.

Candy for each guess 
Find the optimal strategies for 'binary search' played as a game.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Divide the rectangle 
Divide a rectangle into two equal parts, each containing one given cell.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Elementary math 
Compute square roots of numbers and format the output nicely.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Flipping coins 
Find the optimal strategy in a puzzle about guessing your coin without seeing it.

Grid surveillance 
Find a persistent data structure that supports additions and rectangle queries.
Input files:
Easy input data set – G1,
Hard input data set – G2.

HQ09+INCOMPUTABLE?! 
Write a program that outputs your TIS in a very unfriendly language.

Inverting bits 
Compute the negations of many bits using few NOTs.

Jedi academy 
Compute lots of rayobject intersections.
Input files:
Easy input data set – J1,
Hard input data set – J2.

Keep clicking, keep flipping 
Play a game on a graph in which you flip vertex colors and adjacent edges.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Lame crypto 
Break a cryptographic protocol in 'real time'.
Input files:
Easy input data set – L1,
Hard input data set – L2.
Solutions:
Booklet.

My little puppy 
Take care of a virtual puppy for some bonus time.
Solutions:
Booklet.

IPSC 2011 practice session  
Pancakes! 
Maximize the number of pancakes given the resources you have.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Quality of Service 
Assemble the problem statement from many sparse parts.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.
Solutions:
Booklet,
output checker.

Rotate to divide 
Find a number that gets divided by K when we rotate it.
Input files:
Easy input data set – R1,
Hard input data set – R2.

IPSC 2010  Input data packages, Problems and solutions booklet 
Antisort 
Do NOT sort the input sequence.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Broadway 
Find the shortest path in Manhattan that includes the Broadway.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Cells 
Evaluate spreadsheet cells.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Dragon Slayer 
Kill a magic dragon using two magic swords.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Eyjafjallajökull 
Find the vulcano by making online measurements of the ash cloud.
Input files:
Easy input data set – E1,
Hard input data set – E2.
Solutions:
Booklet,
C code implementing a good player.

Flawed Code 
Find inputs for which incorrect greedy algorithms fail.

Grid is good 
Draw a binary tree into a small grid.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Hash 
Invert two hashes that use MD5 incorrectly.

Inside job 
For a dart thrown onto a polygon, compute the expected sum of distances from the dart to all its sides.
Input files:
Easy input data set – I1,
Hard input data set – I2.

Jimmy the Acting Teacher 
Create a schedule of meetings where each pair meets once.
Input files:
Easy input data set – J1,
Hard input data set – J2.

Klingon High Council Training 
Find the optimal strategy for a game played with ships in a 3D grid.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Lovely stamps 
Compute the number of ways in which some stamps can be bought.
Input files:
Easy input data set – L1,
Hard input data set – L2.

Mass psychoanalysis 
Guess two thirds of the average of all guesses.
Solutions:
Booklet.

IPSC 2010 practice session  
Piece of cake! 
Cut a cake shaped like a box in a way that leaves the largest uncut part.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Quick growth 
Memory is being filled by multiplying arrays, compute the sum of all elements.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.

Round and round it goes 
Find constants that turn the given program into the best infinite loop.

IPSC 2009  Input data packages, Problems and solutions booklet 
Arithmetics for dummies 
Find the result of an expression computed on an oldschool calculator.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bouncing balls 
Find the state of a box full of bouncing balls.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Cryptic punchcards 
Read text stored on punchcards.

Don't worry about wrong answers 
A weird problem in which almost any submission is accepted.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Easy representation 
Compute area of a pictorial representation of a correctly parentesized string.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Fish Fillets 
Solve two new levels of the Fish Fillets puzzle.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Going to the movies 
Compute the probability that all girls will find a place to sit at the cinema.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Hunt! 
Direct wolves to hunt sheep in real time.

Instructions 
Implement '+8' and 'next with same popcount' using a very restricted assembler.

Jumbo Airlines 
Compute the number of ways of seating people in an airplane.
Input files:
Easy input data set – J1,
Hard input data set – J2.

Karl's shopping 
Find the smallest amount of additional cash needed when paying by various vouchers.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Let there be rainbows! 
A tree is being colored using 7 colors, construct its final state.
Input files:
Easy input data set – L1,
Hard input data set – L2.

Muzidabutur 
Match regular expressions that are written in verbose English.
Input files:
Easy input data set – M1,
Hard input data set – M2.

IPSC 2009 practice session  
Pathfinding 
Given a maze, find a reasonably short solution.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Quick search 
Given a rectangle divided into polygons, find two identical ones.
Input files:
Easy input,
Hard input.

Reverse quick search 
Create valid test data for problem 'Quick search'.
Input files:
Easy input data set – R1,
Hard input data set – R2.

IPSC 2008  Input data packages 
Army Strength 
Find the winner in a battle of two armies where the weakest unit always gets killed.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Breaking in 
Find the server that gives you the most access when compromised.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Comparison Mysteries 
Show that x==x has a nontrivial solution in ints, and that equality is not transitive.
Solutions:
Solution.

Discover All Sets 
Play a generalized version of the game Sets.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Expected Cost 
Compute the expected cost of a minimum spanning tree for a graph with random edge weights.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Find the Meaning 
A message is somehow hidden in the input file, find it.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Game on Words 
In real time, play against us a game where the players extend a string until it becomes a word.
Input files:
Easy input data set – G1,
Hard input data set – G2.
Solutions:
Solution,
C++ program that plays the game optimally.

Hidden Text 
Show that blurred text can be recovered if you know the font.
Input files:
Easy input data set  H1,
Difficult input data set  H2.

Inventing Test Data 
Given a weighted tree T, find the lightest complete graph for which T is the only MST.
Input files:
Easy input data set – I1,
Hard input data set – I2.

Just a Single Lie 
Find the optimal strategy in a number guessing game where you may receive a single lie.
Input files:
Easy input data set – J1,
Hard input data set – J2.

K Equal Digits 
Find the largest number with all digits equal that matches a set of criteria.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Large party 
Count the ways in which men and women can sit at a table if large clusters of women are forbidden.
Input files:
Easy input data set – L1,
Hard input data set – L2.

IPSC 2008 practice session  
Perfect Rhyme 
Given a word, find another word that is the best rhyme.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Quiz 
Answer all trivia questions about the history of IPSC correctly.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.

Railroad Map 
Given a graph, replace all nonbranching paths by direct edges.
Input files:
Easy input data set – R1,
Hard input data set – R2.

IPSC 2007  Input data packages 
AntiBlot System 
Fix a simple equation that has a ink blot covering part of a number.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bus Story 
Check whether a story about passengers boarding and leaving a bus may be true.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Calling Me Calling You 
Purchase enough free numbers to allow a group of friends call each other for free.
Input files:
Easy input data set – C1,
Hard input data set – C2.
Solutions:
Solution,
C program that solves both data sets.

Delicious Cake 
Count the ways of cutting a rectangular cake into pieces.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Enhancing IPSC Rules 
Given a rockpaperscissors game as a set of pictures, compute who won.

Finally some Sudoku 
Solve several Sudoku instances that share some of their values.
Input files:
Easy input,
Hard input.

Guess the Numbers 
In real time, guess a sequence by choosing another and getting their scalar product.
Input files:
Easy input data set – G1,
Hard input data set – G2.
Solutions:
Solution.

HereThere 
Find the shortest path on a fractal board.
Input files:
Easy input data set – H1,
Hard input data set – H2.

Internet is Faulty 
Minimize the expected transfer time via a network with faulty links.
Input files:
Easy input data set – I1,
Hard input data set – I2.

jPix 
Draw lines and compute area reached by a flood fill on a huge grid.
Input files:
Easy input data set – J1,
Hard input data set – J2.

Know Your Crypto 
Solve a simple cipher and reverse a seemingly random one.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Little Peter's Tower 
Maximize the expected height of a tower built from randomly drawn blocks.
Input files:
Easy input data set – L1,
Hard input data set – L2.

IPSC 2007 practice session  
Paradox With Averages 
If a person moves from group A to group B, the average IQ of both groups may increase.
Input files:
Easy input data set – P1,
Hard input data set – P2.

QuackQuack 
Factorize and duplicate the queue in our special queuebased scripting language.

Rasterized Lines 
Given N, in how many ways can one draw a rasterized line segment with N black pixels?
Input files:
Easy input data set – R1,
Hard input data set – R2.

IPSC 2006  Input data packages 
Another Candies 
Kids brought candies, divide them evenly.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Biased Standings 
Given the teams' wishes, produce a ranklist that matches them as closely as possible.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Counting Subsequences 
Count all contiguous subsequences with sum equal to 47.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Digital Calculator 
Compute the first few and the last few digits of a factorial.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Encoded Messages 
Decrypt a permutation cipher and a substitution cipher.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Fractal Plants 
Find the center of mass of a fractal plant.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Gotta Pick'em All 
Count the largest subsets of {1,...,n} in which no two elements sum to a third one.
Input files:
Input data set – G.

h4x0r t3h c0d3 
Compute a discrete logarithm in a restricted setting, and create two PostScript files with the same MD5 sum.
Input files:
Easy input data set – H1,
Hard input data set – H2.

Ideal Matches 
Cover a complete graph by Hamiltonian cycles that intersect in a fixed matching.
Input files:
Easy input data set – I1,
Hard input data set – I2.
Solutions:
Solution,
A C++ program to solve both data sets.

Jamcode 2006 
Given a task and a wrong program, find an input for which the program works.
Input files:
Easy input data set – J1,
Hard input data set – J2.

Kruskal 
Find the optimal strategy for a NIM variant where creating a primesized heap wins the game.
Input files:
Easy input data set – K1,
Hard input data set – K2.

Librarian 
Create a sequence of page requests that would produce more page faults if cache size is increased slightly.

Matrioska 
Get the correct answer out of multiple nested file formats.
Input files:
Easy input data set – M1,
Hard input data set – M2.
Solutions:
Solution.

IPSC 2006 practice session  
Santos Apples 
Divide a garden into two equal parts, each containing trees of a single type.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Labyrinth 
Simulate a robot in a simple maze.
Input files:
Easy input data set – Q1,
Hard input data set – Q2.

Medical Research 
Given a sequence of numbers, answer queries about the kth smalest one.
Input files:
Easy input data set – R1,
Hard input data set – R2.

IPSC 2005  Input data packages 
Alpha Centauri Tennis 
Given a transcript of a tennis match, find out who won.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bottom Coder 
Alter code so that it creates a specific output.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Crane Operator 
Given a crane and a set of boxes, compute the boxes' final positions and move them using fewest moves possible.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Dance Dance Revolution 
Catch as many arrows as possible in a DDR game.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Exact? Approximate! 
Given a decimal number, produce the simplest fraction that evaluates to that decimal after appropriate rounding.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Find The Right Words 
Given a set of words, assign one to each letter of the alphabet so that each word contains its letter and the total length is minimal.
Input files:
Easy input data set – F1,
Hard input data set – F2.
Solutions:
Solution,
C++ code that solves both data sets.

Gears In Action 
Compute the time until a system of gears reaches a given configuration.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Hidden Messages 
Decrypt two penandpaper ciphers.
Input files:
Easy input data set – H1,
Hard input data set – H2.
Solutions:
Solution.

Ignore the Garbage 
Given an upsidedown digital display, find the kth number that makes sense.
Input files:
Easy input data set – I1,
Hard input data set – I2.

Just for Fun 
Solve logic puzzles for bonus time.
Input files:
Easy input data set – J1,
Hard input data set – J2.
Solutions:
Solution.

IPSC 2005 practice session  
Polly Wanna Cracker 
Divide crackers among parrots evenly and report the exact outcome.
Input files:
Easy input data set – P1,
Hard input data set – P2.

Quack Strikes Back 
Compute Fibonacci numbers and write a backwardsquine in our queuebased scripting language.
Solutions:
Solution.

Rotate And Cut 
Given a string, several times cut one quarter of it off.
Input files:
Easy input data set – R1,
Hard input data set – R2.
Solutions:
Solution,
C code that solves both data sets.

IPSC 2004  Input data packages 
Andrew's revenge 
Given a program and its output, find one matching input.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bishops 
Place the maximum number of bishops on a generalized chessboard.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Calls 
Given a matrix of integers, check whether it is a shortest distances matrix for some graph.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Delayed search 
In real time, guess a number using yes/no questions, with each answer coming only after several questions.
Input files:
Easy input data set – D1,
Hard input data set – D2.
Solutions:
Solution.

Electrical Circuits 
Count the number of perfect matchings in special graphs.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Fat Rat 
Can a sphere fit through a given pipe with obstacles?
Input files:
Easy input data set – F1,
Hard input data set – F2.

Gets and Puts 
Write a sorting program and a quine in our queuebased scripting language.

Hard Question – P=NP? 
Given a polygon and a set of nonintersecting rectangles, does a subset of rectangles exactly match the polygon?
Input files:
Easy input data set – H1,
Hard input data set – H2.

IPSC 2004 practice session  
Dependency Problems 
Given package dependencies and availability, install as many as possible.
Input files:
Easy input data set – R1,
Hard input data set – R2.

Censored Smiles 
Count all smiling faces in a large picture.
Input files:
Easy input data set – S1,
Hard input data set – S2.

The Tiling Problem 
Tile a given floor using 2 by 1 tiles.
Input files:
Easy input data set – T1,
Hard input data set – T2.

IPSC 2003  Input data packages 
Arranging Flowers 
Reconstruct the missing rows of a Latin square.
Input files:
Easy input data set – A1,
Hard input data set – A2.

begin 4 7 add 
Analyze and modify code written in PostScript.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Cinderella 
Using a digital scale, interactively identify the bag with false coins.
Solutions:
Solution.

Dependency Problems 
Given package dependencies and availability, install as many as possible.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Enchanted Forest 
Find the smallest number of flood fills necessary to recolor a 0/1 matrix to a single color.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Folding the Paper 
Can a strip of paper squares be folded into the given order?
Input files:
Easy input data set – F1,
Hard input data set – F2.

Got Root? 
Find the optimal strategy for a Hackenbush variant.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Hordes of Bacteria 
Simulate lots of iterations of a growing bacteria colony.
Input files:
Easy input data set – H1,
Hard input data set – H2.

IPSC 2003 practice session  
Candies 
Separate three candy flavors by moving as few of them as possible.
Input files:
Easy input data set – R1,
Hard input data set – R2.
Solutions:
Correct output – R1,
Correct output – R2.

Colorful Cubes 
Given cubes with colored sides, assemble a tower in which pairs of touching sides match.
Input files:
Easy input data set – S1,
Hard input data set – S2.
Solutions:
Correct output – S1,
Correct output – S2.

Strange Numbers 
Convert integers between binary and our adhoc encoding.
Input files:
Easy input data set – T1,
Hard input data set – T2.
Solutions:
Correct output – T1,
Correct output – T2.

IPSC 2002  
Andews's Exams III 
Given a program, find an input for which it terminates quickly.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Load Balancing 
Find the smallest amount of rounds necessary to rebalance the load for a row of processors.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Chamber of Secrets 
By observing a digital display with a counter few segments at a time, interactively determine its value.

Space Suckers 
Given a graph where each vertex has a set of properties, find a Hamiltonian path such that each property is contiguous.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Expressions 
Express the given number as an expression that uses as few 1s as possible.
Input files:
Easy input data set – E1,
Hard input data set – E2.

(un)Fair Play 
Given a league in progress, find out whether a given team can still win it.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Gardening 
Find the smallest axesparallel square that contains at least one half of the given points.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Equatorial Bonfire 
A set of bonfires is started along the equator, find the time when all the equator is on fire.
Input files:
Easy input data set – H1,
Hard input data set – H2.
Solutions:
Correct output – H1,
Correct output – H2.

IPSC 2002 practice session  
KInARow 
Compute the score for a given game of kinarow.
Input files:
Easy input data set – R1,
Hard input data set – R2.

Candy 
Redistribute candy between packets.
Input files:
Easy input data set – S1,
Hard input data set – S2.

Ice Cream 
Find one Hamiltonian path in a tournament graph.
Input files:
Easy input data set – T1,
Hard input data set – T2.

IPSC 2001  
Andrew's Exams II 
Find the integer printed by an obfuscated program outputs.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Bacteria 
Interactively find a separating line between red and green points.
Input files:
Easy input data set – B1,
Hard input data set – B2.
Solutions:
Solution.

Candies 
Separate three candy flavors by moving as few of them as possible.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Urvi Komu Urvi 
Divide employees into two equal teams, maximizing the number of times a person plays against their boss.
Input files:
Easy input data set – D1,
Hard input data set – D2.

A Censored Smile 
Count all smiling faces in a large picture.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Pibonacci 
Compute the elements of a Fibonaccilike sequence.
Input files:
Easy input data set – F1,
Hard input data set – F2.
Solutions:
Correct output – F1,
Correct output – F2.

Gossipers 
Check whether all gossipers know everything at the end of the day.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Magic 
Find a suitable bijection between two sets of card decks.
Input files:
Easy input data set – H1,
Hard input data set – H2.

IPSC 2001 practice session  
Strange Currency 
Find the largest sum that cannot be paid using given banknotes.
Input files:
Easy input data set – R1,
Hard input data set – R2.
Solutions:
Correct output – R1,
Correct output – R2.

Santo's Apples and Banto's Pears 
Divide a garden into two equal parts, each containing trees of a single type.
Input files:
Easy input data set – S1,
Hard input data set – S2.
Solutions:
Correct output – S1,
Correct output – S2.

IPSC 2000  
KInARow 
Compute the score for a given game of kinarow.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Cake 
Given a set of lines, count into how many parts they divide the plane.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Trolls 
Given a string, interactively guess its correct substring based on its number of occurrences.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Get Back! 
Travel between oases using as little water as possible.
Input files:
Easy input data set – D1,
Hard input data set – D2.
Solutions:
Correct output – D1,
Correct output – D2.

Andrew's Exams 
Count the number of stars an obfuscated program outputs.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Puzzle 
Transform a 0/1 rectangle from one state to another by negating rows and exchanging columns.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Windy Office 
Reconstruct the page order of a program listing, knowing which pages contain which procedures.
Input files:
Easy input data set – G1,
Hard input data set – G2.
Solutions:
Correct output – G1,
Correct output – G2.

Colorful Cubes 
Given cubes with colored sides, assemble a tower in which pairs of touching sides match.
Input files:
Easy input data set – H1,
Hard input data set – H2.
Solutions:
Correct output – H1,
Correct output – H2.

IPSC 2000 practice session  
Santo's Bottles 
From a row of bottles, drink as much as possible without drinking from three consecutive bottles.
Input files:
Easy input data set – R1,
Hard input data set – R2.
Solutions:
Solution,
Program solving both data sets.

Labyrinth 
Simulate a robot in a simple maze.
Input files:
Easy input data set – S1,
Hard input data set – S2.

Coins 
Find counterexamples for greedy algorithms.
Input files:
Easy input data set – T1,
Hard input data set – T2.

IPSC 1999  
Billboard 
Find a 3coloring of the given graph.
Input files:
Easy input data set – A1,
Hard input data set – A2.

Candy 
Redistribute candy between packets.
Input files:
Easy input data set – B1,
Hard input data set – B2.

Coins 
Find counterexamples for greedy algorithms.
Input files:
Easy input data set – C1,
Hard input data set – C2.

Factorial 
Find the last nonzero digit of a factorial.
Input files:
Easy input data set – D1,
Hard input data set – D2.

Labyrinth 
Simulate a robot in a simple maze.
Input files:
Easy input data set – E1,
Hard input data set – E2.

Panel 
Switch rows and columns of bulbs to minimize the number of lit ones.
Input files:
Easy input data set – F1,
Hard input data set – F2.

Rain 
For a given sequence, find the largest k such that no kelement subsequence has a too large sum.
Input files:
Easy input data set – G1,
Hard input data set – G2.

Romeo 
Find out whether two people can meet when following shortest paths.
Input files:
Easy input data set – H1,
Hard input data set – H2.

IPSC 1999 practice session  
Medical Research 
Given a sequence of numbers, answer queries about the kth smalest one.
Input files:
Easy input data set – J1,
Hard input data set – J2.
