All Questions
Tagged with co.combinatorics combinatorial-game-theory
93 questions
19
votes
4
answers
1k
views
Generalization of a mind-boggling box-opening puzzle
Motivation. Suppose we are given $6$ boxes, arranged in the following manner:
$$\left[\begin{array}{ccc} 1 & 2 & 3 \\ 4 & 5 & 6 \end{array}\right]$$
Two of these boxes contain a ...
- 48.9k
14
votes
1
answer
607
views
Is there an elementary proof of a better result for the finite guessing-box puzzle?
The infinitary guessing-box puzzle is amazing — see here. In the basic form, the Guessing-box Hall has infinitely many wooden boxes, each containing a real number, and there are 100 mathematicians ...
- 236k
8
votes
0
answers
82
views
$2$-for-$2$ asymmetric Hex
This is a crosspost from Math stackexchange as I left the question open a while and bountied it but received no answers.
If the game of Hex is played on an asymmetric board (where the hexes are ...
- 181
12
votes
0
answers
495
views
Connection properties of a single stone on an infinite Hex board
This includes a series of questions.
One of the most typical examples is shown as the picture below.
An half-infinite Hex board with an one row of black stones. Black stones are separated by one ...
- 661
4
votes
1
answer
432
views
"Infinity": A card game based on prime factorization and a question
I have been developing a card game called "Infinity", which involves a unique play mechanic based on card interactions. In this game, each card displays a set of symbols, and players match ...
- 3,144
2
votes
0
answers
67
views
How many ways to win a game between two teams with arbitrary player skills
Suppose we have $n\geq 4$ players $p_1,\cdots,p_n$ of a game between two teams: team $A$ and team $B$ (disjoint sets, each with two or more players, so that $|A|+|B|=n$). Assume that each player $p_i$ ...
- 167
7
votes
0
answers
239
views
Chip firing on hypergraphs
A (finite) hypergraph is a pair $(V, \mathcal{E})$ where $V$ is a finite set of vertices and $\mathcal{E}\subseteq\mathcal{P}(V)$ with each $E\in\mathcal{E}$ having at least two elements; a ...
- 20.7k
10
votes
0
answers
386
views
For which set $A$, Alice has a winning strategy?
Cross-posted from MSE: https://math.stackexchange.com/questions/4775193/for-which-set-a-alice-has-a-winning-strategy
Alice and Bob are playing a game. They take an integer $n>1$, and partition the ...
- 1,462
8
votes
1
answer
433
views
Is "do-almost-nothing" ever winning on large CHOMP boards?
This is a special case of a question asked but unanswered at MSE:
Consider the combinatorial game CHOMP (presented as in the linked notes so that the "poison" square is bottom-left). In any $...
- 20.7k
1
vote
0
answers
256
views
The maximum number of moves in a game of Nim [closed]
I was assigned a fun, but also quite hard problem for my computer science class - I have to write a java program that computes the maximum number of turns in an optimal game of Nim.
In case you are ...
- 11
8
votes
1
answer
230
views
Name of a game : Remove two chips from a vertex or one chip from both ends of an edge
Consider a finite graph $\Gamma$ with a positive number $n_v\geq 0$ of chips stacked at each vertex $v$ of $\Gamma$. Two players play in turn with moves consisting either of removing two chips from a ...
- 17.9k
1
vote
1
answer
147
views
Name for an easy combinatorial game
What is the name of the following combinatorial game:
Two players, moving in turn.
Positions: $0,1,2,\ldots$.
Moves: $n\longmapsto n-1$ or $n\longmapsto \lfloor n/2\rfloor$
if $n>0$.
No move for $0$...
- 17.9k
13
votes
0
answers
221
views
A game based on the Euclidean algorithm
The following game is based on a somewhat "stupid" version of the Euclidean algorithm (where we allow only subtractions).
Positions are given by finite non-empty multisets (repeated elements ...
- 17.9k
18
votes
3
answers
666
views
Tic-tac-toe with one mark type
Parameters $a,b,c$ are given such that $c\leq\max(a,b)$. In an $a\times b$ board, two players take turns putting a mark on an empty square. Whoever gets $c$ consecutive marks horizontally, vertically, ...
- 1,209
1
vote
0
answers
85
views
Winning criterion for a combinatorial game
Given $n$,
let $\mathcal{R}$ be a set of pairs $(\rho,A)$
where $A\subseteq n, \rho\in 2^A$.
Consider the following game between A and B.
At each round $t$, A enumerates an $m\in n$ (that has not been ...
- 909
3
votes
0
answers
179
views
What values are representable by Hackenbush stalks?
It is known that every number can be represented by some red-blue Hackenbush stalk (see here, for instance). What values can be represented by red-blue-green Hackenbush stalks? In addition, what games ...
- 131
1
vote
0
answers
136
views
Nim variant with minimum number of objects?
I'm wondering where I can find in the literature (if it exists) a discussion of a Nim variant where we impose the additional condition on Nim that we can remove only up to $c$ objects before the game ...
- 111
3
votes
2
answers
209
views
A "Markov game"
I call games similar to the one I describe below to be Markov games. I am selecting just that one or rather a 1-parameter series of games. The open challenge is to find out which of the players $\ 0\ $...
- 4,786
12
votes
1
answer
361
views
An averaging game on finite multisets of integers
The following procedure is a variant of one suggested by
Patrek Ragnarsson (age 10). Let $M$ be a finite multiset of
integers. A move consists of choosing two elements
$a\neq b$ of $M$ of the same ...
- 50.8k
3
votes
1
answer
234
views
Is following function a metric on the set of isomorphism classes of graphs with countably many vertices?
Suppose $\Gamma_1(V_1, E_1)$ and $\Gamma_2(V_2, E_2)$ are simple graphs with countably many vertices. And suppose $A_1$ and $A_2$ are initially empty sets. Suppose two players play the following game: ...
- 2,618
4
votes
3
answers
240
views
Best strategy for a combinatorial game
Consider the following scenario. We have 20 balls and 100 boxes. We put all 20 balls into the boxes, and each box can contain at most one ball.
Now suppose we are given 5 chances to pick 20 out of ...
- 281
1
vote
0
answers
143
views
Strategy of Responder in Rényi Ulam Liar Games
I tried posting this in Math Stack Exchange but got no responses, so I figured I could try my luck here. My main concern is that I can't figure out how to get started on my "research" (bear with me, I'...
- 11
3
votes
2
answers
180
views
Satisfier-Falsifier games
In a Maker-Breaker game, there is a finite set of elements $X$, and a family $F$ of subsets of $X$ called the "winning sets". Two players, Maker and Breaker, take turns picking untaken elements from $...
- 3,559
6
votes
1
answer
173
views
What is the minimum worst-case length of an element removal game?
A game is played as follows. There is a set $X = \{1, \ldots, n\}$. Player 1 is trying to find a "locally minimal subset" $M \subseteq X$ - that is, player 2 has said that $M$ is good, and also that ...
- 1,331
5
votes
1
answer
204
views
A set-family game
Two players, Green and Red, play a zero-sum game. It is parametrized by two integers $n\geq 0, k\geq 0$, and a finite family $F$ of sets of size $n$ (each set may appear multiple times in $F$).
Each ...
- 3,559
11
votes
2
answers
402
views
Length of optimal play in Hex as a function of size
Consider Hex on an $n \times n$ board without a swap rule, so that the first player wins. Assume the first player tries to minimize the length of the game, and the second player tries to maximize the ...
- 1,808
7
votes
1
answer
356
views
A Bitwise Xor Problem
Consider a sequence $a_i$ defined by
$$
\begin{align*}
a_1&=p,\\
a_2&=q,\\
a_i&=a_{i-1} \oplus a_{i-2}+1,
\end{align*}$$
where $\oplus$ is the bitwise xor operation. How can we give an ...
- 611
27
votes
4
answers
3k
views
Alice and Bob playing on a circle
I want to solve this problem:
Let there be $n \ge 2$ points around a circle. Alice and Bob play a game on the circle. They take moves in turn with Alice beginning. At each move:
Alice takes one ...
- 379
9
votes
3
answers
1k
views
The Sudoku game: Solver-Spoiler variation
Consider the Sudoku Solver-Spoiler game, a natural variation of the Sudoku game recently appearing in the question Who wins two-player Sudoku? posted by user PyRulez. In that game, the players attempt ...
- 236k
19
votes
3
answers
1k
views
The arithmetic progression game and its variations: can you find optimal play?
Consider the arithmetic progression game, a two-player game of
perfect information, in which the players take turns playing
natural numbers, or finite sets of natural numbers, all distinct,
and the ...
- 236k
47
votes
3
answers
5k
views
Does knight behave like a king in his infinite odyssey?
The Knight's Tour is a well-known mathematical chess problem. There is an extensive amount of research concerning this question in two/higher dimensional finite boards. Here, I would like to tackle ...
5
votes
1
answer
6k
views
How many Tic Tac Toe games are possible? [closed]
Consider the average game of Tic Tac Toe or Noughts and Crosses. The game is played on a 3 by 3 two dimentional board. The game is played by two people and each person is allowed to only add one type ...
- 524
22
votes
4
answers
2k
views
The 1-step vanishing polyplets on Conway's game of life
A $n$-polyplet is a collection of $n$ cells on a grid which are orthogonally or diagonally connected.
The number of $n$-polyplets is given by the OEIS sequence A030222: $1, 2, 5, 22, 94, 524, 3031, \...
31
votes
1
answer
1k
views
Vanishing line on Conway's game of life
If the initial state of Conway's game of life is a line of $n \in [0,100]$ alive cells, then it vanishes completely after some steps iff $n \in \{0,1,2,6,14,15,18,19,23,24 \}$. See below for $n=24$.
...
69
votes
7
answers
17k
views
What is a chess piece mathematically?
Historically, the current "standard" set of chess pieces wasn't the only existing alternative or even the standard one. For instance, the famous Al-Suli's Diamond Problem (which remained ...
9
votes
1
answer
389
views
Ordered Nim game
Consider the following variant of Nim:
There are two players and $n$ piles of stones, with sizes $a_1,\dots,a_n$, such that $a_i\leq a_j$ for any $i<j$.
A move consists of removing a positive ...
- 91
9
votes
1
answer
581
views
Is every ordinal the nimber of a ring?
This question is about the game of Noetherian rings, see MO/93276.
Here I will include the zero ring in order to get better formulas.
The nimber of a Noetherian ring is an ordinal number. It is ...
- 63.1k
8
votes
2
answers
372
views
A game of singletons
Alice and Bob play the following zero-sum game, parametrized by two integers $m$ and $k$:
Alice picks $m$ sets, each of which has $k$ items.
Bob colors some items in green.
Bob's score is the number ...
- 3,559
3
votes
1
answer
315
views
Difficulty of 3-color forest Hackenbush
"Forest Hackenbush" (for lack of a better name) is the particular case of the game of Hackenbush where the initial position (and therefore all subsequent positions) is a (finite) forest (:= disjoint ...
- 32.5k
7
votes
1
answer
207
views
Maximum $2$-D bootstrap percolation time for $n$ points on an $n\times n$ grid
I hesitate to ask this question here, but since it remained unanswered after a bounty on MSE, I ask it here with some reservation.
Is the maximum bootstrap percolation time for $n$ points on an $n\...
- 1,903
4
votes
0
answers
309
views
A game played on binary matrices ($2$-dimension coin-turning game)
Let $r\geq 1$ be a natural number. I am interested in the following (two-player, impartial, perfect-information) game:
The state of the game is an $n\times n$ matrix with coefficients in $\mathbb{F}...
- 32.5k
9
votes
1
answer
351
views
A Combinatorial Game with Integer Sequences
Two players, Alice and Bob, take turns constructing a sequence $a_1,a_2,a_3,\dots$, of distinct positive integers, none greater than a given parameter $K$. Alice plays first and makes $a_1=1$. ...
- 3,717
6
votes
0
answers
186
views
Combinatorial game similar to Sprouts
Is there a name for the following combinatorial game? Is there a solution which player has a winning strategy?
Basically this game is "Sprouts without midpoints". One starts with $n$ points in the ...
- 5,482
16
votes
0
answers
988
views
A Combinatorial Game: the Snake and the Hunter
The Snake and the Hunter is a game for two players who play in two rounds interchanging the roles of snake and hunter. The game is played in a rectangular grid of points, say $6 \times 6$. In both ...
- 3,717
4
votes
0
answers
149
views
Combinatorial fairness property in division of goods
Given $n$ agents, and $m$ items where $v_i(g) \geq 0$ is the value of item $g$ for agent $i$, does there always exist a partition $A_1, ..., A_n$ of the $m$ items into $n$ sets s.t. for all $i, j \in \...
- 388
6
votes
1
answer
663
views
A different equivalence relation on partizan combinatorial games
The following definitions are fairly standard, but reworded in a way that will be more appropriate for my question (so what follows is fairly long, but should be easy to read for the experts and might ...
- 32.5k
0
votes
1
answer
205
views
Is the linear production game a convex game?
In cooperative game theory, the linear production game (LPG) is defined by letting the characteristic function have the form of a linear programming problem.
Does anyone know if the LPG is a convex ...
- 17
3
votes
1
answer
492
views
Game on a string
I am interested if one can design an efficient (polynomial) algorithm telling whether the first player has a winning strategy for a game described below.
The board is a string consisting of only ...
- 31
3
votes
1
answer
337
views
Minimal Birthdays
In combinatorial game theory: The birthday of a game is defined recursively as 1 plus the maximal birthday of its options, with the zero game having birthday 0.
Suppose we define the quasi-birthday ...
- 1,129
3
votes
0
answers
715
views
Nimbers and Surreal Numbers [closed]
I have been researching Combinatorial Game Theory. One common theme is the assignment of values to games in order to classify the game as a win for a specific player. One such way is class of surreal ...
- 1,129