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, please state this explicitly in the challenge. If sour…
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A competition to solve a particular problem through the usage and manipulation of strings.
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The challenge involves mathematics. Also consider using more specific tags: [number] [number-theory] [arithmetic] [combinatorics] [graph-theory] [geometry] [abstract-algebra].
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intended to be solved by using, manipulating, accepting as input, or outputting numeric values.
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This challenge involves creating or parsing 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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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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For challenges involving some sort of sequence.
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the amount of code it takes to describe or produce a constant object, such as a string or image. When posting a challenge in this category, please make sure it ad…
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A competition to solve a particular problem through the usage and manipulation of arrays.
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Challenges related to elementary arithmetic.
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For challenges which involve deciding whether or not the input meets certain criteria, and outputting some data, representing that decision.
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a competition where the answer with the highest vote tally (upvotes minus downvotes) wins. As these are frequently closed, read the tag info and post your challenge to the sand…
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Number theory involves properties and relationships of numbers, primarily positive integers.
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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 the manipulation of integers.
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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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intended to be solved by using, manipulating, or creating shapes or other geometric structures.
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Tasks involving random numbers and/or output.
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For challenges about identifying and manipulating prime numbers
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For questions asking for tips on a specific piece of code, to make it a better answer to a programming challenge that is on-topic on this site. Tag [tips] questions with other appropriate tags, s…
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For challenges involving combinatorics.
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generally based upon, related to, or simulates a game or some portion of one.
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For challenges involving a grid.
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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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intended to be solved by using, manipulating, accepting as input, outputting, or calculating calendar dates or clock times.
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a list of numbers arranged in a rectangle with rows and columns. In programming, it is also known as a 2D array. Use this tag if your challenge is about manipulating matrices.
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denotes challenges where parsing input is a large / the main part of the challenge.
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intended to be solved by sorting, ordering, or otherwise organizing some set of data.
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a particular ordering of some list of objects. Problems tagged with permutation usually involve finding or generating permutations, including anagrams of text.
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the base 2 number system. Use this tag for challenges involving base 2.
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For challenges regarding graphs, mathematical structures used to model relations between objects.
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Conversion of numbers between positional numeral systems. Most common systems are decimal, binary, hexadecimal etc.
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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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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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For challenges that involve the physical layout or physical manipulation of source-code.
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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.