## ICS 160E / EECS 114 - Programming Project 2, 50 Points Due: Friday, May 6, 2005, at 11:59pm, using the Checkmate Submission System.

Write a Java program that can play tic-tac-toe effectively. To do this, you will need to create a game tree T, which is a tree where each node corresponds to a game configuration, which in this case is a representation of the tic-tac-toe board. The root node corresponds to the initial configuration. For each internal node v in T, the children of v correspond to the game states we can reach from v's game state in a single legal move for the appropriate player, A (the first player) or B (the second player). Nodes at even depths correspond to moves for A and nodes at odd depths correspond to moves for B. External nodes are either final game states or are at a depth beyond which we don't wish to explore. We score each external node with a value that indicates how good this state is for player A. In large games, like chess, we have to use a heuristic scoring function, but for small games, like tic-tac-toe, we can construct the entire game tree and score external nodes as +1, 0, -1, indicating whether player A has a win, draw, or lose in that configuration. A good algorithm for choosing moves is \emph{minimax}. In this algorithm, we assign a score to each internal node v in T, such that if v represents A's turn, we compute v's score as the maximum of the scores of v's children (which corresponds to A's optimal play from v). If an internal node v represents B's turn, then we compute v's score as the minimum of the scores of v's children (which corresponds to B's optimal play from v).

Note: you may use the following class in your program:

You may read expressions from System.in and output to System.out or use a GUI.