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bittwiddler35

MiniMax and Othello

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Hi, I've used MiniMax trees in the past, but I have run into a kink while applying them to the game of Othello (Reversi). Othello differs, from a game like chess, in that you can leave your opponent ZERO moves and yet the game is not over. I am not sure how to represent this "forced pass" in the game tree. For example I am building the tree and run into a situation where it is Player B's turn to move, but he has no moves and yet Player A DOES have moves from this position. Any help would be appreciated! BT

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I'm not very familiar with Othello but it seems that (in this case) it is a valid move for player B to do nothing. Hence, the sub tree created for this option has one child which is the same as its parent, apart from the player's switching turns as with every branch. Otherwise you could see it as a type of move which has simply no effect. Hope this helps.

Greetz,

Illco

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There's a couple of ways to do it. The first, and more general way, revolves around generalizing minimax so that a player's choice of moves determines who gets to go next. However, in this case, just make it so that when a player has no legal moves, he has exactly one move available to him, one which does not change the board. (also make sure your terminating condition will fire if neither player can move... otherwise your AI will run for a looooong time.)

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