## Play Tic-tac-toe with Arthur Cayley!

Tic-tac-toe, (or *noughts and crosses* or *Xs and Ox*), is a turn-based game for two players who alternately tag the spaces of a $3 \times 3$ grid with their respective marker: an X or an O. The object of the game is to place three markers in a row, either horizontally, vertically, or diagonally. Given only the mechanics of Tic-tac-toe, the game can be expressed as Combinatorial Group by defining a set $A$ of generators $\{a_i\}$ which describe the actions that can be taken by either player. The Cayley Graph of this group can be constructed which will express all the possible ways the game can be played. Using the Cayley Graph as a model, it should be possible to learn the Tic-tac-toe game tree using dynamic programming techniques (hint: the game tree is a sub-graph of the Cayley Graph).

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