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.

Problems in geometry or graph theory that involve finding an optimal (e.g. shortest) path, subject to constraints (obstacles).
115 questions
For challenges which consist of two adversary (and asymmetric) sub-challenges.
115 questions
related to the Python language. Note that challenges that require the answers to be in a specific language are generally discouraged.
111 questions
For challenges focusing on the optimization of an aspect not covered by other tags.
109 questions
For challenges regarding counting the number of occurrences of some characteristic.
109 questions
Tasks involving writing interpreters for various languages or formalisms.
108 questions
Problems involving processing of natural languages in a human way. Tasks include interpreting free text, correcting spelling or grammar, understanding pronunciation, etc.
101 questions
The challenge involves Fibonacci numbers or one of their generalizations.
95 questions
For challenges involving code that runs in multiple programming languages.
90 questions
a strategic game played with two players on a checkered grid. This tag is for challenges related to chess or any variation on chess.
88 questions
related to the JavaScript language. Note that challenges that require the answers to be in a specific language are generally discouraged.
88 questions
Code challenges that involve the use of regular expressions.
85 questions
Challenges pertaining to a sequence within a larger sequence
83 questions
if your challenge is about writing programs that solve puzzles such as Sudoku, Rubik's Cube, Crossword puzzles, etc.
83 questions
Related to compressing or decompressing arbitrary data. Challenges which relate to compressing a single specific input should instead be tagged [kolmogorov-complexity]
82 questions
words, phrases, representations of numbers or times which read the same in reverse, for example "level", "reviver", "12321", "10:01". See also the [balanced-string] tag.
81 questions
indicates that the challenge requires answers to use the Internet to retrieve information.
77 questions
In a balanced string certain pairs of characters or substrings always appear with the same amount. Often there are additional restrictions that those pairs also have to be ordered. The most common exa…
75 questions
For challenges involving the usage and manipulation of the alphabet.
72 questions
This challenge involves the manipulation of rational numbers, i.e. those which can be represented as a fraction of integers. Do not use this tag if rational numbers are just one of several admissible …
71 questions
A challenge that involves making a "Hello, World!" program, or other similar strings.
71 questions
related to the BF language. Note that challenges that require the answers to be in a specific language are generally discouraged.
71 questions
indicates that the challenge involves converting from one format to another.
71 questions
The solution can only contain the 95 printable ASCII characters (space to ~). Tabs and newlines may be allowed as well, depending on the challenge.
70 questions
For challenges which involve card games. This includes playing the game, implementing the game, as well as challenges concerned with individual mechanics and analysis of the game (for instance, comput…
69 questions
scored by the number of operations in a specific fragment of a language you define.
68 questions
for challenges involving board games.
68 questions
indicates that the challenge involves music, e.g. taking music as input, producing music as output or handling musical notes.
67 questions
expected to generate code.
67 questions
For challenges involving unicode.
66 questions
For challenges involving doing something on the bit level.
62 questions
For challenges involving cryptography: encryption or decryption.
61 questions
shapes that are self-similar and are usually quite detailed. Well-known fractal sets include the Mandelbrot set, Julia sets, and Phoenix sets. Tree-like fractal drawings are also common…
60 questions
code for these challenges will create some form of animated output
60 questions
Challenges which involve computing probabilities for random variables and stochastic processes.
57 questions
won by the answer with the smallest asymptotic time complexity. For challenges based on actual runtime, use [fastest-code] instead.
56 questions
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