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Questions tagged [tic-tac-toe]

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

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42 votes
6 answers
25k 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?
Xynariz's user avatar
  • 3,622
6 votes
2 answers
2k 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"): $$ \...
klm123's user avatar
  • 16.2k
36 votes
1 answer
2k 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 ...
Hugh Meyers's user avatar
  • 23.7k
15 votes
3 answers
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 ...
MWilliams's user avatar
  • 1,058
12 votes
3 answers
3k 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 ...
xnor's user avatar
  • 27k