The game of tic-tac-toe, also spelled ticktacktoe and also known as 3-in-a-row or "naughts and crosses," is a game in which players alternate placing pieces (typically Xs for the first player and Os for the second) on a board. The first player to get three pieces in a row (vertically, horizontally, or diagonally) is the winner.For the usual board, a drawcan always be obtained, making it a futile game.A generalized -in-a-row on an board can also be considered, as can a generalization to a three-dimensional "board." The game consisting of getting five (or more) in a row on a board variously considered to be of size or is known as go-moku. The specific case of tic-tac-toe is known as qubic.For 2-in-a-row on any board larger than , the first player has a trivial win. In "revenge" tic-tac-toe (in which -in-a-row wins, but loses if the opponent can make -in-a-row on the next move), even 2-in-a-row is non-trivial. For instance, on a board is won for the first player if he starts in the second or fourth square, but not if he starts elsewhere.
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