# Tagged Questions

Combinatorial game theory (abbreviated CGT) is the subfield of combinatorics (not traditional game theory) which deals with games of perfect information such as Nim and Go. It includes topics such as the Sprague-Grundy theorem and is tangentially related to the Surreal Numbers.

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### The Ring Game on $K[x,y,z]$

I recently read about the Ring Game on MathOverflow, and have been trying to determine winning strategies for each player on various rings. The game has two players and begins with a commutative ...
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### Sharing a pepperoni pizza with your worst enemy

You are about to eat a pepperoni pizza, which is sliced into eight pieces. Each pepperoni will unambiguously belong to some slice (no pepperoni is "between" slices). The caveat is that you have to ...
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### Maximum board position in 2048 game

A game called 2048 is making rounds on social media. I am trying to determine the maximum score attainable for this game. Let's assume WLOG that only 2s are returned (if 4s are possible the max score ...
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### Guaranteed Checkmate with Rooks in High-Dimensional Chess

Given an infinite (in all directions), $n$-dimensional chess board $\mathbb Z^n$, and a black king. What is the minimum number of white rooks necessary that can guarantee a checkmate in a finite ...
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### Three against the devil: a combinatorial game

A team of three sinners plays a game against the devil. They confer on strategy beforehand; then they go into three separate rooms, and there is no more communication between them. The play in each ...
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### A 20+ year old combinatorial problem - the cookie game

Learned about this not too long after the time of the original problem publication through a classmate who visited MIT one summer. http://faculty.uml.edu/jpropp/cookie2.pdf The problem goes as ...
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### The expected outcome of a random game of chess?

Imagine a game of chess where both players generate a list of legal moves and pick one uniformly at random. Q: What is the expected outcome for white? 1 point for black checkmated, 0.5 for a ...
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### What is the optimal strategy in the “Factor Game”?

Edit (Nov 1, 2015): Bounty awarded, but the full question (i.e., what is the optimal strategy) remains open at the time of this update. Consider the Factor Game played as follows: Given a list of ...
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### Game involving points on $[0,1]$

You're given a list of $22$ points in $[0,1]$ (not necessarily distinct), and you're asked to select, at every iteration, $2$ points to be substituted by their midpoint. After $20$ iteration, you ...
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### Is it true that we can get zero for all $(x,y,z)\in\mathbb{N}^3$?

There are three distinct positive integers $x$, $y$, and $z$. We can choose two numbers $a,b\in\{x,y,z\}$, where $b\leq a$, then replace $b$ by $2b$ and replace $a$ by $a-b$. Is it true that there ...
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### A game on a graph

Alice and Bob play a game on a complete graph ${G}$ with $2014$ vertices. They take moves in turn with Alice beginning. At each move Alice directs one undirected edge of $G$. At each move Bob chooses ...
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### Number of moves to solve a flood-it/sock-dye game

[ Question based on the sock dye game ] [ Update: It appears that this game is better known as "Flood it" and is NP-hard. Also, "the number of moves required to flood the whole board is $\Omega(n)$ ...
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### Reference for combinatorial game theory.

What is a good reference material for elementary combinatorial game theory? By combinatorial game theory I mean chiefly the study of zero-sum, deterministic two-player games (perhaps even more ...
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### Average Scrabble graph structure: diameter?

Tonight a game of Scrabble ended in what I consider a very unusual graph structure, unlike this generic web image, which seems more typical:           ...
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### How many possible board states in 2048?

I recently found out about the famous 2048 game. For those of you who don't know how it works, it consists on a 4x4 board on where tiles which are powers of 2 are placed. On every turn, you "swipe" ...
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### Analyzing a class of vertex-deletion games

As part of the discussion on this question (Permutation Game Redux), a simple vertex-deletion game was proposed. The game is very simple. Disconnect. Players alternately remove vertices from a ...
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### Game to maintain distinct number of balls in glasses

There are $n$ glasses, containing $n+1,n+2,\ldots,2n$ balls, respectively. Two players $A$ and $B$ play a game, alternately taking turns with $A$ going first. In each move, the player must choose some ...
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### perfect play in 1-dimensional Minesweeper

In 1-dimensional Minesweeper with a known number of mines (that are distributed uniformly), is there a known somewhat-simple strategy for perfect play? When there are n cells and [0 or n-1 or n]...
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### “Infinito”, a combinatorial game with infinite width game-tree

I recently designed a combinatorial game (sequential game of perfect information) with an infinite branching factor, that is it has a game-tree of infinite width. I'm wondering how is it possible to ...
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### Solving Chess - alternatives to brute force

It is well known that solving Chess is practically impossible using brute force methods. I'm interested to know if there have been any serious attempts using alternate methods. What theory and ...
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### NIM with multiple winning final positions

I've been looking at a variant of NIM. You can skip this bit where I'll describe NIM as usually described: There's a starting position with some number of piles of counters and two players ...
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### Number of cycles in a grid such that each cycle traverse all the lines

Definition: An edge-component is a sequence of some consecutive collinear-segments. Consider an $n \times n$ grid-like arrangement of $2n$ lines. Is there any idea about the number of simple cycles ...
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### Modify the rules of Gomoku (Five-in-a-row) or Connect Four type games to enforce the fairness among players

One colleague and me were discussing this problem during lunch today, and I did a little bit digging for several hours after returning to my office. Fact: For an $(m,n,k)$-game, there does not exist ...
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### How many turns can a chess game take at maximum?

The shortest number of moves that a game of chess can have is 2, as far as I know: White moves pawn from f2 to f3, black moves ...
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### Characteristic 3 analogue of nimbers?

Finite nimbers are a way of turning the natural numbers (finite ordinals) into a characteristic 2 field. Addition in this field is found by writing the numbers in binary and adding without carry, ...
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### Why are the surreals considered “recreational” mathematics?

One of my college math professors once remarked to me that it was interesting that John Conway's two "biggest" contributions to math were both recreational: the Game of Life and the Surreals. No one, ...
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### Proving that one has solved chess by exhibiting the zeroes of polynomials over finite fields?

My question is based on one of Scott Aaronson blog post which states that a God-like being could convinced the villagers, to any degree of confidence, that she has solved chess by answering a few ...
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### A Nim-like game with conditions and strategies

The game: Given $S = \{ a_1,..., a_n \}$ of positive integers ($n \ge 2$). The game is played by two people. At each of their turns, the player chooses two different non-zero numbers and subtracts $1$...
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### Converting a Gomoku winning strategy from a small board to a winning strategy on a larger board

Gomoku is the game where Black and White take turns placing stones of their own color, and the winner is the player who first gets five of their own stones in a row. Black moves first. In Gomoku on ...
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### Game replacing two numbers by mean

Alicia and Bart plays a game. Alicia first writes $100$ real numbers on the board. After that they move alternately; Bart goes first. In every move, the player chooses two numbers, erases them, and ...
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### Wizard against two dwarfs: guess the whole function

An evil wizard plays the following game with two dwarfs $A$ and $B$: he thinks of a function $f:\mathbb{R}\to\mathbb{R}$ (which is not required to have any regularity properties, such as measurability,...
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### Winning strategies in multidimensional tic-tac-toe

This question is a result of having too much free time years ago during military service. One of the many pastimes was playing tic-tac-toe in varying grid sizes and dimensions, and it lead me to a ...
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### What is the winning strategy for this Game on the Power Set

Given a finite set, players alternately choose proper subsets. Once a subset has been chosen, none of its subsets may be chosen later. The last player to move wins. I figured out that, with optimal ...
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### How can a Devil catch a Fool in the Angel and Devils game?

The Angel and Devils game (http://en.wikipedia.org/wiki/Angel_problem) is a two-player game, played on an infinite chessboard (i.e. the integer coordinates of $\mathbb{R}^2$). One player is the angel, ...
I'm thinking about some game theory problem. Here it is, Problem: Consider the polynomial equation $x^3+Ax^2+Bx+C=0$. A priori, $A$,$B$ and $C$ are "undecided", yet and two players "Boy" and "Girl"...