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.
For challenges involving data on a hexagonal grid. Use this tag also for triangular grids, the dual of the hexagonal grid (that is, the vertices of the hexagonal grid form the faces of the triangular …
for challenges involving an output (graphical or ASCII-art) which changes with time.
Fastest-algorithm competitions are won by the answer with the smallest asymptotic time complexity. For challenges based on actual runtime, use [fastest-code] instead.
Abstract Algebra is the study of algebraic structures, including groups, rings, fields, vector spaces, and the like.
Challenges with a spec which requires all answers to meet certain time complexity restrictions. This could be specific ("Your answer must be O(n^2) where n is the number of items in the input"), or at…
Indicates that the challenge involves the manipulation of binary matrices, matrices whose elements are all one of two possible values, typically 1 and 0, or True and False.
For challenges involving cryptography, including things like ciphers and hashing algorithms
Classification challenges involve grouping input data into certain classes based on the properties of that data.
for challenges involving the mathematical constant pi, the ratio of a circle's circumference to its diameter.
This challenge is related to the C language. Note that challenges that require the answers to be in a specific language are generally discouraged.
For challenges related to the subdivision of a set into smaller disjoint sets. This also includes the subdivision of ordered collections like lists, and non-discrete sets like intervals. Challenges sh…
Related to chemistry or some aspect of chemistry
Puzzles involving cellular automata, such as Conway's Game of Life.
Metagolf is golfing the output of a metaprogram. A metaprogram produces a program which solves a given task, and the length of that output determines the score of the original program.
For challenges relating to manipulating and traversing the file system. This may include reading directory trees, creating, moving and deleting files or directories, reading or changing file permissio…
For challenges related to the different ways of expressing an integer as a sum of positive integers.
exists for historical reasons. New challenges of the type previously posted under this tag are not welcome.
For challenges involving a keyboard or keyboard layouts, such as QWERTY and AZERTY.
for a challenge involving the mathematical operator of division or integer division
For challenges that involve partitioning a space (usually the plane) into small tiles without gaps (usually using a finite set of proto-tiles). See also [set-partitions].
For challenges involving linear algebra, the mathematics of vector spaces and linear mappings between them.
An answer-chaining challenge is a challenge where previous answers to the challenge influence how new answers are produced.
for challenges relating to mazes, typically generating or navigating them. This often is used with the [ascii-art] tag, a common method of demonstrating the mazes
For challenges involving simulation.
A problem whose scoring criterion involves running the output of a program through a large number of test cases.
For challenges involving stack-like data structures (see tag wiki for details), including interpreters of stack-based programming languages and challenges specifically about call stacks.
a challenge to build objects (e.g. code, representation of real world objects) according to pre-defined rules and/or input (also often randomised).
This challenge is related to the Java language. Note that challenges that require the answers to be in a specific language are generally discouraged.
A busy beaver maximises some property of the computation model (e.g. execution time, memory usage, output length) subject to the constraint that it must halt.
This challenge relates to data expressed under a different representation or language (including encoding, decoding, and processing such data). Some examples of an encoding includes ASCII and UTF-8.
Set theory is the branch of mathematics that studies unordered collections of objects. Challenges with this tag will involve the manipulation or analysis of sets.
For challenges related to the processing and placement of whitespace characters (mainly, but not limited to spaces, tabs and line feeds), like challenges related to indentation. For challenges about t…
A programming puzzle includes a goal, a partially completed program, and rules outlining how the program can be modified. The program is specifically designed to make achieving the goal difficult. An …
For challenges pertaining to problems in the field of Physics.
for challenges related to the functional programming paradigm.
For challenges involving ways to organize data (data types, arrays, binary trees ...)