Solution.cpp

class Solution {
public:
    vector<vector<char>> updateBoard(vector<vector<char>>& board, vector<int>& click) {
        int m = board.size(), n = board[0].size();
        int i = click[0], j = click[1];

        function<void(int, int)> dfs = [&](int i, int j) {
            int cnt = 0;
            for (int x = i - 1; x <= i + 1; ++x) {
                for (int y = j - 1; y <= j + 1; ++y) {
                    if (x >= 0 && x < m && y >= 0 && y < n && board[x][y] == 'M') {
                        ++cnt;
                    }
                }
            }
            if (cnt) {
                board[i][j] = cnt + '0';
            } else {
                board[i][j] = 'B';
                for (int x = i - 1; x <= i + 1; ++x) {
                    for (int y = j - 1; y <= j + 1; ++y) {
                        if (x >= 0 && x < m && y >= 0 && y < n && board[x][y] == 'E') {
                            dfs(x, y);
                        }
                    }
                }
            }
        };

        if (board[i][j] == 'M') {
            board[i][j] = 'X';
        } else {
            dfs(i, j);
        }
        return board;
    }
};