使用蒙特卡洛树搜索完成反四子棋bot的c++代码实现

蒙特卡洛树搜索是一种常用的人工智能算法，可以用于解决许多博弈问题。下面是一个使用蒙特卡洛树搜索完成反四子棋bot的c++代码实现，供您参考。

首先，需要定义一个棋盘的类，该类中包含棋盘的状态和一些基本操作，例如判断胜负、落子等操作。

const int N = 5;
const int M = 5;
const int K = 4;

enum ChessType { EMPTY, BLACK, WHITE };

class Board {
public:
    ChessType board[N][M];

    Board() {
        memset(board, 0, sizeof(board));
    }

    bool putChess(int x, int y, ChessType type) {
        if (x < 0 || x >= N || y < 0 || y >= M || board[x][y] != EMPTY) {
            return false;
        }
        board[x][y] = type;
        return true;
    }

    bool checkWin(ChessType type) {
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                if (board[i][j] == type) {
                    if (checkLine(i, j, 1, 0, type)) {
                        return true;
                    }
                    if (checkLine(i, j, 0, 1, type)) {
                        return true;
                    }
                    if (checkLine(i, j, 1, 1, type)) {
                        return true;
                    }
                    if (checkLine(i, j, 1, -1, type)) {
                        return true;
                    }
                }
            }
        }
        return false;
    }

    bool checkLine(int x, int y, int dx, int dy, ChessType type) {
        for (int i = 1; i < K; i++) {
            int nx = x + i * dx;
            int ny = y + i * dy;
            if (nx < 0 || nx >= N || ny < 0 || ny >= M || board[nx][ny] != type) {
                return false;
            }
        }
        return true;
    }
};

接下来，需要定义一个蒙特卡洛树节点的类，该类中包含节点的状态和一些基本操作，例如展开节点、模拟游戏等操作。

const int MAXN = 10000;

class Node {
public:
    int cnt;
    double val;
    Board board;
    Node *parent;
    vector<Node *> children;

    Node(Board board, Node *parent = nullptr) :
        cnt(0), val(0), board(board), parent(parent) {}

    void expand() {
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                if (board.board[i][j] == EMPTY) {
                    Board newBoard = board;
                    newBoard.putChess(i, j, BLACK);
                    children.push_back(new Node(newBoard, this));
                }
            }
        }
    }

    double simulate() {
        Board simBoard = board;
        int cnt = 0;
        while (!simBoard.checkWin(BLACK) && !simBoard.checkWin(WHITE)) {
            int x = rand() % N;
            int y = rand() % M;
            if (simBoard.putChess(x, y, WHITE)) {
                cnt++;
            }
        }
        return cnt;
    }

    double uct(int totalCnt) {
        return val / cnt + sqrt(2 * log(totalCnt) / cnt);
    }

    Node *select() {
        Node *cur = this;
        while (!cur->children.empty()) {
            double maxUct = -1e9;
            Node *maxNode = nullptr;
            for (auto child : cur->children) {
                double uctVal = child->uct(cnt);
                if (uctVal > maxUct) {
                    maxUct = uctVal;
                    maxNode = child;
                }
            }
            cur = maxNode;
        }
        return cur;
    }

    void update(double val) {
        cnt++;
        this->val += val;
        if (parent != nullptr) {
            parent->update(val);
        }
    }
};

最后，需要定义一个反四子棋bot的类，该类中包含基本操作，例如初始化、落子等操作。

class AntiFourBot {
public:
    Board board;
    Node *root;

    AntiFourBot() {
        root = new Node(board, nullptr);
    }

    void putChess(int x, int y) {
        for (auto child : root->children) {
            if (child->board.board[x][y] != board.board[x][y]) {
                root = child;
                break;
            }
        }

        board.putChess(x, y, BLACK);

        for (auto child : root->children) {
            if (child->board.board[x][y] == WHITE) {
                root = child;
                break;
            }
        }

        root->expand();

        for (int i = 0; i < MAXN; i++) {
            Node *cur = root->select();
            double val = cur->simulate();
            cur->update(val);
        }

        for (auto child : root->children) {
            if (child->board.board[x][y] == WHITE) {
                root = child;
                break;
            }
        }

        board.putChess(root->board.board[x][y], WHITE);
        root = new Node(board, nullptr);
    }
};

可以通过以下代码来测试反四子棋bot的性能：

int main() {
    AntiFourBot bot;
    while (true) {
        int x, y;
        cin >> x >> y;
        bot.putChess(x, y);
        cout << bot.root->board.board << endl;
    }
    return 0;
}