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Let $G$ be a graph with $n$ vertices. The {\em hat guessing number} of $G$ is defined in terms of the following game: There are $n$ players and one opponent. The opponent will wear one of the $q$ hats of different colors on the player's…

Combinatorics · Mathematics 2023-02-09 Lanchao Wang , Yaojun Chen

In this article, we look at a hat-guessing game, in which each player must guess the color of their own hat while only seeing the hats of the other players. We focus on the case of two hat colors and a countably infinite number of players.…

Probability · Mathematics 2025-10-28 Nathaniel Eldredge

We study the hat chromatic number of a graph defined in the following way: there is one player at each vertex of a loopless graph $G$, an adversary places a hat of one of $K$ colors on the head of each player, two players can see each…

Combinatorics · Mathematics 2019-05-13 Bartłomiej Bosek , Andrzej Dudek , Michał Farnik , Jarosław Grytczuk , Przemysław Mazur

We study the hat guessing game on graphs. In this game, a player is placed on each vertex $v$ of a graph $G$ and assigned a colored hat from $h(v)$ possible colors. Each player makes a deterministic guess on their hat color based on the…

Combinatorics · Mathematics 2023-12-05 Jeremy Chizewer , I. M. J. McInnis , Mehrdad Sohrabi , Shriya Kaistha

The hat guessing number is a graph invariant based on a hat guessing game introduced by Winkler. Using a new vertex decomposition argument involving an edge density theorem of Erd\H{o}s for hypergraphs, we show that the hat guessing number…

Combinatorics · Mathematics 2025-09-30 Peter Bradshaw

The prisoners and hats puzzle, or simply the hat puzzle, is a family of games in which a group of prisoners are each assigned a colored hat and are asked to guess the color of their own hat. Various versions of the puzzle arise depending on…

Logic · Mathematics 2025-11-13 Souji Shizuma

Lionel Levine's hat challenge has $t$ players, each with a (very large, or infinite) stack of hats on their head, each hat independently colored at random black or white. The players are allowed to coordinate before the random colors are…

Combinatorics · Mathematics 2021-03-10 Ehud Friedgut , Gil Kalai , Guy Kindler

A puzzle about prisoners trying to identify the color of a hat on their head leads to a version where there are k more hats than prisoners. This generalized puzzle is related to the independence number of the arrangement graph A(m, n) and…

Combinatorics · Mathematics 2019-03-25 Rob Pratt , Stan Wagon , Michael Wiener , Piotr Zielinski

We study a combinatorial coloring game between two players, Spoiler and Algorithm, who alternate turns. First, Spoiler places a new token at a vertex in $G$, and Algorithm responds by assigning a color to the new token. Algorithm must…

Combinatorics · Mathematics 2017-12-27 Kevin G. Milans , Michael C. Wigal

2023 undergraduate thesis on a deterministic "hat game." For a digraph $D$, each player stands on a vertex $v$, is assigned a hat from $h(v)$ possible colors, and makes $g(v)$ guesses of her hat's color based on her out-neighbors' hats. If…

Combinatorics · Mathematics 2025-07-30 I. M. J. McInnis

We initiate the study of the hat guessing number of a graph where the adversary is only allowed to provide a proper coloring of the graph. This is the largest number $q$ for which there is a guessing strategy on each vertex that only…

In this paper we study the Three Hat Problem which appeared in Puzzle Corner of the Technology Review magazine. This puzzle gives a scenario in which three players wearing hats are sitting together and each hat can be seen by everyone…

History and Overview · Mathematics 2007-10-16 Brian Benson , Yang Wang

The network coloring game has been proposed in the literature of social sciences as a model for conflict-resolution circumstances. The players of the game are the vertices of a graph with $n$ vertices and maximum degree $\Delta$. The game…

Discrete Mathematics · Computer Science 2022-04-01 Nikolaos Fryganiotis , Symeon Papavassiliou , Christos Pelekis

We start with the well-known game below: Two players hold a sheet of paper to their forehead on which a positive integer is written. The numbers are consecutive and each player can only see the number of the other one. In each time step,…

Combinatorics · Mathematics 2013-02-26 Felix Günther , Irina Mustata

This paper studies asymmetric Ebert's Hat Problem with five players where the probability of the colors may be unequal. We obtain maximal winning probabilities and optimal winning strategies using the concept of adequate sets.

Combinatorics · Mathematics 2023-06-07 Theo van Uem

We consider Lionel Levine's notorious hat puzzle with two players. Each player has a stack of hats on their head, and each hat is chosen independently to be either black or white. After observing only the other player's hats, players…

Probability · Mathematics 2025-03-13 Steven Heilman , Omer Tamuz

Consider the following hat guessing game. A bear sits on each vertex of a graph $G$, and a demon puts on each bear a hat colored by one of $h$ colors. Each bear sees only the hat colors of his neighbors. Based on this information only, each…

Combinatorics · Mathematics 2024-02-14 Václav Blažej , Pavel Dvořák , Michal Opler

The Levine hat game requires $n$ players, each wearing an infinite random stack of black and white hats, to guess the location of a black hat on their own head seeing only the hats worn by all the other players. They are allowed a strategy…

Motivated by the success of domination games and by a variation of the coloring game called the indicated coloring game, we introduce a version of domination games called the indicated domination game. It is played on an arbitrary graph $G$…

Combinatorics · Mathematics 2024-03-28 Boštjan Brešar , Csilla Bujtás , Vesna Iršič , Douglas F. Rall , Zsolt Tuza

We study the Levine hat problem, a cooperative puzzle introduced by Lionel Levine in 2010, in which $n \geq 2$ players must simultaneously identify a black hat on their own infinite stack, each seeing only their teammates' stacks. While the…

Combinatorics · Mathematics 2026-04-21 Clément Bouquet , Salah Chikhi , Timothé Charles , Yanghao Zhou , Eric Wang