A minimax search computes an optimal move in a two-player sequential game that is a finite game, has perfect
information, and is a zero-sum game. The possible
continuations form a rooted tree in which each position
is joined to the positions reachable by one legal move. If is the set of positions reachable
in one move from
and
is the payoff at a terminal position, the game
value is determined recursively by
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(1)
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An optimal move for the maximizing player leads to a position with the largest game value, while an optimal move for the minimizing player leads to one with the smallest game value. Unlike the minimax theorem, which is an existence theorem for optimal mixed strategies, minimax search is a recursive algorithm for exploring the possible moves.