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public class ChessAI {
private static final int MAX_DEPTH = 3;
public static Move findBestMove(Board board) {
int bestScore = Integer.MIN_VALUE;
Move bestMove = null;
for (Move move : board.getAllLegalMoves(true)) {
board.move(move);
int score = minimax(board, MAX_DEPTH, Integer.MIN_VALUE, Integer.MAX_VALUE, false);
board.undoMove();
if (score > bestScore) {
bestScore = score;
bestMove = move;
}
}
return bestMove;
}
private static int minimax(Board board, int depth, int alpha, int beta, boolean maximizingPlayer) {
if (depth == 0 || board.isGameOver) {
return evaluateBoard(board);
}
int score;
if (maximizingPlayer) {
score = Integer.MIN_VALUE;
for (Move move : board.getAllLegalMoves(true)) {
board.move(move);
score = Math.max(score, minimax(board, depth - 1, alpha, beta, false));
board.undoMove();
alpha = Math.max(alpha, score);
if (beta <= alpha) {
break;
}
}
} else {
score = Integer.MAX_VALUE;
for (Move move : board.getAllLegalMoves(true)) {
board.move(move);
score = Math.min(score, minimax(board, depth - 1, alpha, beta, true));
board.undoMove();
beta = Math.min(beta, score);
if (beta <= alpha) {
break;
}
}
}
return score;
}
private static int evaluateBoard(Board board) {
Score score = new Score();
board.forEachPiece((coordinate, piece) -> {
if (!piece.black) {
score.add(-piece.getValue());
} else {
score.add(piece.getValue());
}
});
return score.score;
}
}
class Score {
public int score;
public void add(int value) {
score += value;
}
}