NP-complete problems

Sudoku (; ; originally called Number Place) is a logic-based, combinatorial number-placement puzzle. In classic Sudoku, the objective is to fill a 9 × 9 grid with digits so that each column, each row, and each of the nine 3 × 3 subgrids that compose the grid (also called "boxes", "blocks", or "regions") contains all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which, for a well-posed puzzle, has a single solution.

Tetris () is a puzzle video game created by Alexey Pajitnov, a Soviet software engineer, in the mid-1980s. In Tetris, falling pieces consisting of four connected blocks, known as tetrominoes, must be sorted into a pile. Once a horizontal line of the playfield is filled with blocks, the line disappears, granting points and preventing the pile from reaching the top. This gameplay has been used in approximately 220 versions across at least 70 platforms. Newer versions frequently add game mechanics, some of which have become standard. , Tetris is the second-best-selling video game series, with ove

process by which a man-made object is deconstructed to reveal its designs, architecture, code or to extract knowledge from the object

NP-hard problem in combinatorial optimization

logic puzzle video game genre

assignment of colors to elements of a graph subject to certain constraints

number game with 15 pieces but 16 spaces

thumb|250px|An easy Kakuro puzzle thumb|250px|Solution for the above puzzle Kakuro or Kakkuro or Kakoro () is a kind of logic puzzle that is often referred to as a mathematical transliteration of the crossword. Kakuro puzzles are regular features in many math-and-logic puzzle publications across the world. In 1966, Canadian Jacob E. Funk, an employee of Dell Magazines, came up with the original English name Cross Sums and other names such as Cross Addition have also been used, but the Japanese name Kakuro, abbreviation of Japanese kasan kurosu (加算クロス, "addition cross"), seems to have gained ge

path in a graph that visits each vertex exactly once

thumb|upright=0.8|It can be difficult to find a valid solution to a Sudoku puzzle, but once a solution has been found its validity can be verified easily. It is NP-complete to determine whether an Sudoku has a valid solution.

problem in combinatorial optimization

thumb|A completed nonogram of the letter "W" from the Wikipedia logo

problem of determining if a Boolean formula could be made true

board game

board game for one player

integer that is a perfect square modulo some integer

mathematical model of ferromagnetism in statistical mechanics

set of vertices in a graph, no two of which are adjacent

in graph theory, the problem to find a shortest closed path or circuit that visits every edge of an undirected graph

FreeCell is a solitaire card game played using the standard 52-card deck. It is fundamentally different from most solitaire games in that very few deals are unsolvable, and all cards are dealt face-up from the beginning of the game. It was originally created as a computer game by Paul Alfille. Microsoft has included an implementation of FreeCell in every release of the Windows operating system since 1995, which has greatly contributed to the game's popularity.

overview about the mathematics of paper folding

mathematical optimization problem in which variables are restricted to be integers

Alignment of more than two molecular sequence

the problem of finding a sequence that is a subsequence of each of a given set of sequences and is as long as possible

a puzzle of reconstructing equations that have been enciphered into words

computational problem of finding cliques in a graph

Hashiwokakero (橋をかけろ Hashi o kakero; lit. "build bridges!") is a type of logic puzzle published by Nikoli. It has also been published in English under the name Bridges or Chopsticks (based on a mistranslation: the hashi of the title, 橋, means bridge; hashi written with another character, 箸, means chopsticks). It has also appeared in The Times under the name Hashi. In France, Denmark, the Netherlands, and Belgium it is published under the name Ai-Ki-Ai.

logic puzzle

right|thumb|240px|Example of a Hitori puzzle Hitori (Japanese: "Alone" or "one person"; Hitori ni shite kure; literally "leave me alone") is a type of logic puzzle published by Nikoli.

an assignment of colors to the edges of a graph so that no two edges that share an endpoint have the same color as each other

a set of vertices in a node-link graph such that every vertex is either in the set or adjacent to it

class of problems in combinatorial mathematics

a set of vertices that includes at least one endpoint of every edge in a graph

mathematical problems defined as a set of objects whose state must satisfy a number of constraints or limitations

classical problem in combinatorics

combinatorial optimization problem about the optimal set of routes for a fleet of vehicles to traverse in order to deliver to a given set of customers

set of computational problems

thumb|right|class=skin-invert-image|Moderately difficult Slitherlink puzzle (Media:Slitherlink-answer.png|solution) Slitherlink (also known as Sli-Lin, Fences, Takegaki, Loop the Loop, Loopy, Ouroboros, Suriza, Rundweg, Tectonic and Dotty Dilemma) is a logic puzzle developed by publisher Nikoli.

the problem of finding a simple path of maximum length in a given graph

normal form used in database normalization which removed all redundancies based on functional dependencies

computational problem in graph theory

concept in graph theory

solitaire game played with mahjong tiles

2001 video game

a structure-preserving correspondence between node-link graphs

align molecular sequences using sequence and structural information

is a logic puzzle published by Nikoli.

a cut of a graph whose size is at least the size of any other cut

abstract model to describe execution of transactions running in the system

thumb|right|Sample puzzle thumb|right|Solution to above puzzle is a type of logic puzzle designed and published by Nikoli. The purpose of its creation was to present a puzzle that uses no numbers or letters and yet retains depth and aesthetics.

the NP-complete problem of testing whether one graph is a subgraph of another

logic puzzle

problem of finding a minimal clique cover of a given graph

subdivision of vertices into disjoint sets

problem of determining whether a mathematical formula is satisfiable

In graph theory, the treewidth of an undirected graph is an integer number which specifies, informally, how far the graph is from being a tree. The smallest treewidth is 1; the graphs with treewidth 1 are exactly the trees and the forests. An example of graphs with treewidth at most 2 are the series–parallel graphs. The maximal graphs with treewidth exactly are called -trees, and the graphs with treewidth at most are called partial -trees. Many other well-studied graph families also have bounded treewidth.

graph whose vertices are or can be partitioned into multiple different independent sets

a set of vertices in a node-link graph whose deletion eliminates all cycles in the graph

intrinsic property of undirected graphs

branch of discrete mathematics