Game Trees
Jouni Smed, Harri Hakonen · 2017
This chapter concentrates on two-player perfect information zero-sum games. A game has the zero-sum property when one player's gain equals another player's loss, whereas in a non-zero-sum game one player gains more than the other loses. All possible plays of a perfect information game can be represented in a game tree: the root node is the initial position, its successors are the positions the first player can reach in one move, their successors are the positions resulting from the second player's responses, and so forth. In two-player perfect information games, the first player of the round is commonly called MAX and the second player MIN. Hence, a game tree contains two types of nodes, MAX nodes and MIN nodes. A ply is the length of the path between two nodes. The minimax method gives the best zero-sum move available for the player at any node in the game tree.