Java实现象棋算法的示例代码

public int search(int depth, int alpha, int beta) {
    // 达到搜索深度或游戏结束，返回当前局面分数
    if(depth == 0 || gameover()) {
        return evaluate();
    }
    
    // 每一层轮流极大值或极小值
    if(currentPlayer == AI) { // AI玩家
        int best = Integer.MIN_VALUE;
        for(Move move : generateMoves()) {
            makeMove(move);
            int val = search(depth - 1, alpha, beta);
            unmakeMove(move);
            best = Math.max(best, val);
            alpha = Math.max(alpha, best);
            if(beta <= alpha) {
                // beta剪枝
                break;
            }
        }
        return best;
    } else { // 对手玩家
        int best = Integer.MAX_VALUE;
        for(Move move : generateMoves()) {
            makeMove(move);
            int val = search(depth - 1, alpha, beta);
            unmakeMove(move);
            best = Math.min(best, val);
            beta = Math.min(beta, best);
            if(beta <= alpha) {
                // alpha剪枝
                break;
            }
        }
        return best;
    }
}

public int evaluate() {
    int val = 0;
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 9; j++) {
            int piece = board[i][j];
            if(piece != EMPTY) {
                // 考虑棋子的价值
                int value = pieceValue[piece];
                if(player[piece] == HUMAN) {
                    value = -value;
                }
                val += value;
                
                // 考虑棋子的位置
                int x = (player[piece] == AI) ? i : (9 - i);
                int y = (player[piece] == AI) ? j : (8 - j);
                val += positionValue[piece][x][y];
                
                // 考虑棋子的连通性
                boolean connected = false;
                for(int k = 0; k < 4; k++) {
                    int nx = i + dx[k];
                    int ny = j + dy[k];
                    if(nx >= 0 && ny >= 0 && nx < 10 && ny < 9) {
                        if(board[nx][ny] == piece) {
                            connected = true;
                            break;
                        }
                    }
                }
                if(connected) {
                    val += connectedValue[piece];
                }
                
                // 考虑是否将军
                if(isThreatened(i, j, player[piece] == HUMAN)) {
                    val += (player[piece] == AI) ? CHECK_SCORE : -CHECK_SCORE;
                }
            }
        }
    }
    return val;
}

public int alphaBetaSearch(int depth) {
    int bestVal = Integer.MIN_VALUE;
    int alpha = Integer.MIN_VALUE;
    int beta = Integer.MAX_VALUE;
    List<Move> moves = generateMoves();
    Move bestMove = null;
    for(Move move : moves) {
        makeMove(move);
        int val = search(depth - 1, alpha, beta);
        unmakeMove(move);
        if(val > bestVal) {
            bestVal = val;
            bestMove = move;
        }
        alpha = Math.max(alpha, bestVal);
        if(beta <= alpha) {
            // beta剪枝
            break;
        }
    }
    makeMove(bestMove);
    return bestVal;
}