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 characters or bytes of source code. If source code length is not the primary scoring criterion, consider using another tag instea…
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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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a competition where the correct answer with the highest vote tally (upvotes minus downvotes) wins, usually the most creative answer.
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The challenge involves mathematics. Also consider using more specific tags: [number] [number-theory] [arithmetic] [combinatorics] [graphs] [geometry].
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intended to be solved by using, creating, or resolving some processing algorithm.
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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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A competition to solve a particular problem through the usage and manipulation of strings.
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intended to be solved by using, manipulating, accepting as input, or outputting numeric values.
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determined by the runtime performance of the submissions. For scoring by asymptotic time complexity, use [tag:fastest-algorithm] instead. "Faster, faster would …
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generally based upon, related to, or simulates game or some portion of one.
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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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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 ASCII art output, use [tag:ascii-art]. For images as input, use [tag:image-processing].
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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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a program which produces its source as output. This tag indicates that the challenge is related to quines.
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in the process of being replaced with [programming-puzzle] and [puzzle-solver]. Please don't use it on new questions.
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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.
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a number that is only divisible by 1 and itself.
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Tasks involving random numbers and/or output.
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related to the C language. Note that challenges that require the answers to be in a specific language are generally discouraged.
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Questions related to elementary arithmetic.
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intended to be solved by sorting, ordering, or otherwise organizing some set of data.
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for challenges involving combinatorics.
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Number theory involves properties and relationships of numbers, primarily positive integers.
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Tasks involving writing interpreters for various languages or formalisms.
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for challenges involving some sort of sequence.
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A challenge that involves making a Hello world program.
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related to the C++ language. Note that challenges that require the answers to be in a specific language are generally discouraged.
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for challenges involving optimizing a certain thing.
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King-of-the-hill indicates a game where the submissions compete against each other.
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Code challenges that involve the use of regular expressions.
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related to the JavaScript language. Note that challenges that require the answers to be in a specific language are generally discouraged.
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related to the Python language. Note that challenges that require the answers to be in a specific language are generally discouraged.
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a strategic game played with two players on a checkered grid. This tag is for challenges related to chess or any derivative of it.
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intended to be solved by using, manipulating, accepting as input, outputting, or calculating calendar dates.
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related to the BF language. Note that challenges that require the answers to be in a specific language are generally discouraged.