A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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a competition to solve a particular problem in the fewest bytes of source code. If you want to score by characters instead of bytes, state this explicitly in the challenge. If source code…
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a competition for creative ways to solve a programming puzzle with an objective winning criterion not covered by other scoring tags (e.g. code-golf).
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The challenge involves mathematics. Also consider using more specific tags: [number] [number-theory] [arithmetic] [combinatorics] [graphs] [geometry] [field-theory].
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A competition to solve a particular problem through the usage and manipulation of strings.
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a competition where the correct answer with the highest vote tally (upvotes minus downvotes) wins, usually the most creative answer.
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This challenge involves creating pictures using text characters as the paint. Typically this uses only 95 printable (from a total of 128) characters defined by the ASCII Standard from 1963.
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intended to be solved by using, manipulating, accepting as input, or outputting numeric values.
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the amount of code it takes to produce a given string of text. When posting a challenge in this category, please make sure it adds something new to the challenges…
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This challenge involves drawing pictures on a screen or generating image files. For pure ASCII art contests, use [ascii-art] instead. If participants can choose between graphics and ASCII art, use bot…
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For challenges involving some sort of sequence.
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Imposes a restriction on the source code used to solve the challenge, for example, having no numbers in the source code.
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Questions related to elementary arithmetic.
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Tips for either golfing or programming challenges. In most current cases it is for helpful tips and tricks how one could golf more effectively with a particular language.
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generally based upon, related to, or simulates a game or some portion of one.
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intended to be solved by using, manipulating, or creating shapes or other geometric structures.
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Number theory involves properties and relationships of numbers, primarily positive integers.
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for challenges involving combinatorics.
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A competition to solve a particular problem through the usage and manipulation of arrays.
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a program which produces its source as output. This tag indicates that the challenge is related to quines.
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Tasks involving random numbers and/or output.
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a number that is only divisible by 1 and itself.
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determined by the runtime performance of the submissions. For fairness, all submissions should be benchmarked on the same machine, which usually means all sub…
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For challenges involving a grid.
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intended to be solved by using, manipulating, accepting as input, outputting, or calculating calendar dates or clock times.
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King-of-the-hill indicates a game where the submissions interact with and compete against each other in some form of game. Competitions which pit programs against each other without interaction should…
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Problems relating to graph theory
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These challenges involve processing pre-existing image files, by altering them in some way, gathering statistics, or other image processing tasks.
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intended to be solved by sorting, ordering, or otherwise organizing some set of data.
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Tasks involving writing interpreters for various languages or formalisms.
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denotes challenges where parsing input is a large / the main part of the challenge.
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for challenges involving optimizing a certain thing.
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a problem designed to test ingenuity. Questions in this category ask for a program which can substitute for that ingenuity.
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Problems in geometry or graph theory that involve finding an optimal (e.g. shortest) path, subject to constraints (obstacles).
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Conversion of numbers between positional numeral systems. Most common systems are decimal, binary, hexadecimal etc.
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For challenges that involve the physical layout or physical manipulation of source-code.
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A challenge to write a program that looks like it does one thing, but, in reality, does something else. Votes reflect how non-obvious the bug is.