# Internet Problem Solving Contest

## Errata for the Problem Statements

For most problems, the original problem statements found on the IPSC website and in the downloadable archives should contain all the information you need to solve them. But in some cases, we had to publish additional clarifications or corrections during the contest. This page collects these announcements.

Additionally, while the Training Area faithfully reproduces most of the unique rules and special problems used in the history of IPSC, some problems had to be modified to work in the new format. (If you find that some problem or special rule isn't working as it should, and it's not mentioned on this page, please tell us! It's probably a bug.)

### IPSC 1999-2003

No global announcements have been preserved. Perhaps there weren't any.

### IPSC 2004

Problem D (Delayed search): Some teams were unable to submit problem D due to a technical issue. The contest was extended and the teams were given another chance to solve the problem. You do not get this chance in the Training Area. The virtual contest takes 6 hours, but you can only submit for the first 5 hours. For the last hour, you can merely watch the other teams solve problem D and overtake you in the ranklist. Sorry!

Problem G (Gets and Puts): The quine in G2 has to be non-empty.

Problem H (Hard Question – P=NP?): The example input is incorrect. The first line of the input in the example should be 4 2. (There are only two rectangles.)

### IPSC 2005

Problem Q (Quack Strikes Back): The einuq in Q2 has to be non-empty.

Problem B (Bottom Coder): The example for problem B1 is incorrect. Use a single letter Q as the separator.

Problem C (Crane Operator): The second condition in the problem statement is slightly wrong. It should say:

2. Numbers x and y are nonnegative integers chosen in such a way that pi≠M mod N and no previous box was assigned to the location pi
Also note that different boxes can have different values of x and y. They should more properly be called xi and yi.

Problem J (Just For Fun): In the J1 puzzle "palindrome", previous means previous from the given date, not previous from today.

### IPSC 2006

Problem C (Counting Subsequences): The input file c2.in is missing a blank line before the first test case. (All the numbers in the file are correct.)

Problem H (h4x0r t3h c0d3): There is no automatic judging script for subproblem H2. In 2006 we checked the submissions by hand. (Or rather, we would have if there were any.) Therefore, problem H2 cannot be sumitted in the Training Area.

Problem G (Gotta Pick'em All): To clarify, you are not allowed to pick up three distinct cards A, B, C such that A+B=C. For example, the correct number of cards for N=4 is 3, and there are two ways to pick them: {1,2,4} and {2,3,4}.

### IPSC 2007

Problem H (Here-There): The input specification is wrong. It should say:

Each test case consists of five integers D, Hc, Tc, Hr, Tr, specifying the degree of the board D, the coordinates of Here (Hc, Hr) and the coordinates of There (Tc, Tr).
This has been fixed in the online problem statement, but it still affects the downloadable archives and problem statements.

### IPSC 2008

Problem I (Inventing Test Data): In the example input, the explanation should read "between nodes 1 and 3", not "between nodes 2 and 3". This has been fixed in the online problem statement, but it still affects the downloadable archives and problem statements.

### IPSC 2009

Problem H (Hunt!): This problem is not yet available in the Training Area. The judging scripts are a bit harder to port than for other problems. If you'd like to see it, tell us – send us an e-mail to the address in the footer.

### IPSC 2010

Problem E (Eyjafjallajökull): A more detailed description of the coordinate system:
When you change the X coordinate, you move horizontally, when you change the Y coordinate, you move vertically.
On the wind matrix, (-2,-2) is the upper left corner.
X grows to the right, Y grows downwards, as is usual with discrete arrays.

Problem F (Flawed Code): An early version of the problem statement incorrectly stated that Alla's solution takes 10 cubes. The correct value is 15.

Problem H (Hash): In IPSC 2010, every team was assigned a random 20-digit number called a TIS (Team Identification String). In the Training Area version of this problem, assume your TIS is "31415926535897932384". (A proper solution should work for any 20-digit number.)

Problem M (Mass psychoanalysis): While you can still gain bonus minutes in the Training Area, only submissions made in the original contest count towards the average.

### IPSC 2011

Problem H (HQ0-9+-INCOMPUTABLE?!): In IPSC 2011, every team was assigned a random 20-digit number called a TIS (Team Identification String). In the Training Area version of this problem, assume your TIS is "31415926535897932384". (A proper solution should work for any 20-digit number.)

Problem L (Lame crypto) and M (My little puppy): These problems are not yet available in the Training Area. The judging scripts for these problems are in a huge mess and would likely need a complete rewrite to work. If you'd like to see them, tell us – send us an e-mail to the address in the footer.

### IPSC 2012

Problem D (Data mania): Anything that is listed as a country (including "_no_specific_country_") is a country. Anything that is listed as an institution is an institution.

Problem H (Harvesting potatoes): The input specification is wrong. The constraints for the easy input are actually "r,c ≤ 20", not "r,c ≤ 12".

No errata.

### IPSC 2014

Problem T (Two covers): The input specification is wrong. Both subproblems should contain "1 ≤ k ≤ ℓ" instead of "1 ≤ k ≤ n".

Problem C (Copier): Unfortunately, the downloadable archives do not contain the correct inputs for C1. Please download `c1.in` directly from the website.

Problem F (Find a sudoku in π): The problem statement originally contained a small typo in the introduction. The sequence that occurs at offset 5 is "9265", not "9256".

Problem H (Hashsets): On our machine, `sizeof(size_t) == 8` in C++.

Problem J (Judging programs): In subproblem J2, only instances where start != end are valid. (The problem statement should have stated "two distinct endpoints".) If a program only fails when start == end, it is still considered good.

Problem L (Let there be sound): Some teams are having problems with determining the exact value of a certain large number in L1. As this was not intended to be a part of the problem, we decided to help you out by letting you know that the number ends in 99.

### IPSC 2015

General: You need to install Python 2 and the Pygame library for some IPSC 2015 problems. You can test your installation using this package.

Problem D (Dijkstra's Nightmare): Graphs that contain negative cycles will be rejected by the grader. This is consistent with the Python version of the reference implementation. (The C++ version of the reference implementation will actually terminate on such graphs because its long longs will eventually overflow. Please pretend that this does not happen. ;) Thanks to Mykhailo Granik for pointing this out.)

Problem E (Enclosure): The Pygame client needs the file cat.png, which is missing from the downloadable archives. Please download it separately.

Problem H (Humble Captains): In the example annotation, we had a typo: "and their difference is 0" should obviously say "and their difference is 1". This is now fixed (except in the downloadable archives).

Problem U (Unusual Game Show): Clarification: The contestant does know the probability p. On the other hand, when she plays the game she doesn't know whether Monty is tired for that specific game.

### IPSC 2016

Problem C (Counting swaps): The PDF version has a typo in the example - the first line of the input should obviously be 3, not 2.

No errata.