Guide on statements | Articles

  1. Problem name

    • Follow common title capitalization rules when writing English problem names. Example: «The Best of the Problems» instead of «The best of the problems». This is not applicable to Ukrainian statements.

    • Avoid using any special characters in problem names (&\(^\wedge\)@* or similar).

    • Must not be too long (7 words or fewer).

    • Problem name must be unique in both English and Ukrainian (there should be no problem with the same name in the archive).

  2. Limits

    • Default time limit: 2 s.

    • Default memory limit: 256 MB.

    • Time limit up to 7 s.

    • Memory limit up to 1024 MB, at least 128 MB, and must be a power of 2.

    • If time or memory limit is less than the default, make sure it’s well solvable in Java and Python.

  3. Paragraphs

    • Separate paragraphs with an empty line in LaTeX; don’t use paragraph indentation or \par command.

    • The statement must not be a single large paragraph. Split the statement into multiple logical paragraphs for readability purposes.

  4. Variables

    • By default, all statement and input variables must be enclosed in $, for example: $n$.

    • Variables must not be bold.

    • It’s recommended to keep variable names single-letter and lower-case.

    • Use common variable names when available (e. g. \(n\) for the number of vertices, \(m\) for the number of edges, \(k\) or \(q\) for the number of requests).

    • Avoid indexing variable names (e. g. \(i\) or \(j\)) as input variables.

  5. Literals

    • Literal numbers must not be enclosed in $. Example: Vertices are numbered from 1 to $n$, inclusive. Exception: if the statement requires outputting -1 when the answer does not exist, treat -1 as a literal string (see below).

    • Literal strings must be enclosed in \texttt{}. For example, use \texttt{YES} when describing positive output string.

    • Do not use quotes for literal strings.

    • Numbering literals (or variables) must have a proper ending, e. g. the 2-nd, the $i$-th, etc. The same holds for the Ukrainian language

    • Array literals must not be enclosed in $, for example, [4, 7].

  6. Formulas

    • All mathematical formulas must be enclosed in $, for example: $n < m$.

    • Don’t use * for multiplication. Use \cdot instead (e. g. $n \cdot m$).

    • Use \times for matrix dimension description, e. g. matrix of size $n \times m$.

    • Don’t use division sign /. Use fraction instead: $ \frac{a}{b}$.

    • Use proper LaTeX commands as inequality signs: \le for ’less than or equal’, \ge for ’greater than or equal’.

    • Large formulas must be placed on a separate line and centered by enclosing in $$ (double dollar-sign), for example: $$n < m$$.

    • Use ^ and _ for sup and sub, for example: $10^9$, $2^{nk}$, $a_i$.

    • Always use appropriate LaTeX commands when describing math symbols. Refer to this page for the full list of possible math commands.

    • Arrays (except literals) should be written as the following: $[a_1, a_2, \ldots, a_n]$.

  7. Input

    • Always specify if the input token is an integer, float, string, or single character.

    • If the input contains floats, it must be clearly stated what format is expected.

    • Use the following style when describing input in English: The first line of the input contains a pair of integers ..., The following $m$ lines describe..., etc. Always use proper English articles.

    • Do not leave input over-simplified, e. g. avoid One integer $n$. Instead, write: The first line of input contains one integer $n$ – number of bottles.

    • Each variable in the input must be briefly described.

  8. Output

    • If it’s possible to have no answer, it should be clearly stated in the output section.

    • If there are multiple possible answers, it should be stated in the output section.

    • If it’s guaranteed that for the given input there’s always an answer, this should be stated in the output section.

    • If the answer contains float numbers, the output section must specify the allowed precision (absolute and/or relative).

    • If the answer has to be output modulo some number, it should be stated in the output section. It should be explicitly stated if the modulo number is prime.

    • Use the following style when describing output in English: Print a single integer denoting the minimum number ... etc. Always use proper English articles.

    • Do not leave output over-simplified, e. g. avoid Answer to the problem. Instead, write: In one line print single integer n – number of bottles.

  9. Constraints

    • All constraints must be placed in the dedicated section of the statement. It’s allowed to copy constraints in the main statement section for emphasis purposes.

    • Combine constraints when appropriate: $1 \le n, m \le 1000$.

    • Each constraint inequality must be placed in a separate line of the statement (hence separated by an empty line in LaTeX).

    • Length of a string must be denoted as |s|.

    • Use proper inequality signs (as described in the Formulas section).

    • Always try to make constraint numbers as readable as possible. For example, write $1 \le n \le 2 \cdot 10^9$ instead of $1 \le n \le 2000000000$.

    • Use round or lucky numbers as constraints.

    • Each constraint line should end with a comma, the last one - with a dot. Any statement (except the first one) should start in a lower-case.

  10. Lists

    • Use proper LaTeX commands for lists:

      Unordered (bulletpoint) list:
       \item One entry in the list
       \item Another entry in the list
      Ordered (numerated) list:
       \item One entry in the list
       \item Another entry in the list
  11. Images

    • All images must be uploaded in the Resources section of an Algotester problem.

    • Images are referenced by resource name without file extension.

    • Images must be centered by default, with the image description below:

       \caption{A picture of a gull.}
  12. Samples

    • A statement must contain at least one sample.

    • Avoid too trivial samples (aka Boiko samples).

    • The first sample must be the first test case of the problem. The same holds for the following samples, if any.

    • There is an opportunity to create samples only for statement.

  13. Notes

    • The Notes section must contain sample descriptions when appropriate.

    • The Notes section can also contain additional definitions when needed, but they must also be referenced in the main statement.

  14. Miscellaneous

    • Parts of the statement that need special emphasis (non-obvious constraints or conditions, corrected parts of the statements, etc.) must be bold (enclosed in \textbf{}).

    • Use --- in Ukrainian and -- in English, never use - as a long dash.

    • Use spell-checker when writing English and Ukrainian statements.