Questions tagged [tic-tac-toe]

Puzzles centered around tic-tac-toe (a.k.a. noughts and crosses).

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36
votes
5answers
9k views

What is the optimal first move in tic-tac-toe?

I have been told that it is possible to guarantee no worse than a tie in normal 3x3 tic-tac-toe, but that the first move is very important. What is that important first move?
35
votes
1answer
1k views

Titanic Tic-Tac-Toe

Xavier and Oliver were playing tic-tac-toe on the Titanic using a wooden board and metal X's and O's. As the stern of the ship sank lower and lower they found, to their annoyance, that the pieces ...
20
votes
2answers
1k views

Titanicker Tic-Tac-Toe

This is something of a follow-on to Hugh Meyer's enjoyable "Titanic Tic-Tac-Toe." Fortunately, our intrepid heroes Xavier and Oliver have wrested away a bit of wreckage that some fellow named Jack was ...
16
votes
2answers
1k views

Tic-Tac-Toe variant

To help people think this out, I've made a web game with increasingly difficult cpu players to allow brainstorming and testing strategies: cpu player, easiest (version 1 - at least 5-in-a-row is ...
15
votes
3answers
1k views

N-dimensional Tic-Tac-Toe variant

Consider the game surface to be an infinite N dimensional Cartesian lattice. The rules are X moves first, but O gets to move ...
13
votes
2answers
2k views

Tic-Tac-Toe Without a Predefined Board

On a warm and uneventful summer day, John and Mary passed the time by playing games of Tic-Tac-Toe, taking sticks and drawing in the soil. John and Mary are both child prodigies, so within two rounds ...
13
votes
2answers
921 views

Devising a sudoku where the rows are the moves for a draw in tic tac toe

The task is to construct a sudoku whose rows (or columns) are the moves for a game in tic tac toe where the game ends in a draw. Here are some clarifications and constraints which should limit ...
12
votes
3answers
2k views

Tic-tac-toe 1000 in a row

Consider a variant of Tic-Tac-Toe and Gomoku on a board that's infinite in every direction. X wins by getting a line of 1000 X's ...
11
votes
1answer
625 views

A Tic-Tac-Toe variant with three marks - winning strategy and chances

We start with a usual $3 \times 3$ grid, $3$ different marks (say, $X, O, I$) and $2$ players. Player $A$ has to make a vertical, horizontal or diagonal line made of $3$ identical marks (XXX, OOO or ...
7
votes
1answer
982 views

Tic-Tac-Toe problem

In an infinite grid of regular triangles, Niels and Henrik are playing a game they made up. Every other time, Niels picks a triangle and writes × in it, and every other time, Henrik picks a triangle ...
7
votes
1answer
778 views

Tic Tac Toe Recursive

Related: Connect 4 Recursive We have a mega tic tac toe grid. Each of the nine cells of the mega grid has a smaller tic tac toe grid. In total we have 81 cells that can be filled. (Maybe imagine a ...
5
votes
2answers
792 views

What is the smallest tic-tac-toe board to have a winning strategy?

There is not winning strategy for 9cell 3x3 board. There is a winning strategy for 16cell 4x4 board, or even for 10cell "3x3 + 1_cell_near_a_corner" board (see M.Gardner "Mathematical games"): $$ \...
2
votes
1answer
345 views

Another Tic-Tac-Toe problem

Two players A and B play Tic-Tac-Toe on an infinite 3-dimensional grid. Player A starts first and uses X, player B plays second and uses O. Every time player A places an X on the grid, player B can ...
1
vote
0answers
127 views

Tic Tac Toe and random turn puzzle [closed]

I have a problem: There is a bag of 75 balls with 15 Red and rest Blue. I pick 4 balls at the start of every turn.If I get to pick at least 1 red ball, I fill 1 cell with X. If I get 3 red balls ...
-4
votes
2answers
575 views

Optimal running-time tic-tac-toe algorithm

A perfect tic-tac-toe AI/algorithm would ideally never lose, but only win or draw, 100% of the time. Imagine that you play against once such algorithm, and it calculates the next move to make. Is ...