public class Solution {

    //DFS

        public char[,] UpdateBoard(char[,] board, int[] click)

        {

            int m = board.GetLength(), n = board.GetLength();

            int row = click[], col = click[];

            if (board[row, col] == 'M')

            { // Mine

                board[row, col] = 'X';

            }

            else

            { // Empty

                // Get number of mines first.

                int count = ;

                for (int i = -; i < ; i++)

                {

                    for (int j = -; j < ; j++)

                    {

                        if (i ==  && j == ) continue;

                        int r = row + i, c = col + j;

                        if (r <  || r >= m || c <  || c <  || c >= n) continue;

                        if (board[r, c] == 'M' || board[r, c] == 'X') count++;

                    }

                }

                if (count > )

                { // If it is not a 'B', stop further DFS.

                    board[row, col] = (char)(count + '');

                }

                else

                { // Continue DFS to adjacent cells.

                    board[row, col] = 'B';

                    for (int i = -; i < ; i++)

                    {

                        for (int j = -; j < ; j++)

                        {

                            if (i ==  && j == ) continue;

                            int r = row + i, c = col + j;

                            if (r <  || r >= m || c <  || c <  || c >= n) continue;

                            if (board[r, c] == 'E') UpdateBoard(board, new int[] { r, c });

                        }

                    }

                }

            }

            return board;

        }

        ////BFS

        //public char[,] UpdateBoard(char[,] board, int[] click)

        //{

        //    int m = board.GetLength(0), n = board.GetLength(1);

        //    Queue<int[]> queue = new Queue<int[]>();

        //    queue.Enqueue(click);

        //    while (queue.Count > 0)

        //    {

        //        int[] cell = queue.Dequeue();

        //        int row = cell[0], col = cell[1];

        //        if (board[row, col] == 'M')

        //        { // Mine

        //            board[row, col] = 'X';

        //        }

        //        else

        //        { // Empty

        //            // Get number of mines first.

        //            int count = 0;

        //            for (int i = -1; i < 2; i++)

        //            {

        //                for (int j = -1; j < 2; j++)

        //                {

        //                    if (i == 0 && j == 0) continue;

        //                    int r = row + i, c = col + j;

        //                    if (r < 0 || r >= m || c < 0 || c < 0 || c >= n) continue;

        //                    if (board[r, c] == 'M' || board[r, c] == 'X') count++;

        //                }

        //            }

        //            if (count > 0)

        //            { // If it is not a 'B', stop further DFS.

        //                board[row, col] = (char)(count + '0');

        //            }

        //            else

        //            { // Continue BFS to adjacent cells.

        //                board[row, col] = 'B';

        //                for (int i = -1; i < 2; i++)

        //                {

        //                    for (int j = -1; j < 2; j++)

        //                    {

        //                        if (i == 0 && j == 0) continue;

        //                        int r = row + i, c = col + j;

        //                        if (r < 0 || r >= m || c < 0 || c < 0 || c >= n) continue;

        //                        if (board[r, c] == 'E')

        //                        {

        //                            queue.Enqueue(new int[] { r, c });

        //                            board[r, c] = 'B'; // Avoid to be added again.

        //                        }

        //                    }

        //                }

        //            }

        //        }

        //    }

        //    return board;

        //}

}

public char[,] UpdateBoard(char[,] board, int[] click)

        {

            var row = board.GetLength();//行数

            var col = board.GetLength();//列数

            var visited = new bool[row, col];//默认为全为false            

            var i = click[];

            var j = click[];

            if (board[i, j] == 'M')

            {

                board[i, j] = 'X';

                return board;

            }

            else

            {

                Queue<int[]> Q = new Queue<int[]>();

                var coord = new int[] { i, j };

                Q.Enqueue(coord);

                var list = new List<int[]>();//存储有效节点

                while (Q.Any())

                {

                    var position = Q.Dequeue();

                    //获取新的坐标

                    var x = position[];

                    var y = position[];

                    visited[x, y] = true;//当前点被访问

                    //根据毗邻元素更新当前地板的标记

                    var minecount = ;//八个方向毗邻地板的地雷个数

                    list.Clear();

                    //左上

                    var left_top = new int[] { x - , y -  };

                    if (left_top[] >=  && left_top[] >=  && !visited[left_top[], left_top[]])

                    {

                        if (board[left_top[], left_top[]] == 'M')

                        {

                            minecount++;//探测得一枚地雷

                        }

                        else

                        {

                            list.Add(left_top);//暂存有效节点

                        }

                    }

                    //正上

                    var top = new int[] { x - , y };

                    if (top[] >=  && !visited[top[], top[]])

                    {

                        if (board[x - , y] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(top);

                        }

                    }

                    //右上

                    var right_top = new int[] { x - , y +  };

                    if (right_top[] >=  && right_top[] <= col -  && !visited[right_top[], right_top[]])

                    {

                        if (board[right_top[], right_top[]] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(right_top);

                        }

                    }

                    //正右

                    var right = new int[] { x, y +  };

                    if (right[] <= col -  && !visited[right[], right[]])

                    {

                        if (board[right[], right[]] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(right);

                        }

                    }

                    //右下

                    var right_bottom = new int[] { x + , y +  };

                    if (right_bottom[] <= row -  && right_bottom[] <= col -  && !visited[right_bottom[], right_bottom[]])

                    {

                        if (board[right_bottom[], right_bottom[]] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(right_bottom);

                        }

                    }

                    //正下

                    var bottom = new int[] { x + , y };

                    if (bottom[] <= row -  && !visited[bottom[], bottom[]])

                    {

                        if (board[bottom[], bottom[]] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(bottom);

                        }

                    }

                    //左下

                    var left_bottom = new int[] { x + , y -  };

                    if (left_bottom[] <= row -  && left_bottom[] >=  && !visited[left_bottom[], left_bottom[]])

                    {

                        if (board[left_bottom[], left_bottom[]] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(left_bottom);

                        }

                    }

                    //正左

                    var left = new int[] { x, y -  };

                    if (left[] >=  && !visited[left[], left[]])

                    {

                        if (board[left[], left[]] == 'M')

                        {

                            minecount++;

                        }

                        else

                        {

                            list.Add(left);

                        }

                    }

                    //毗邻的八个位置都没有地雷

                    if (minecount == )

                    {

                        //当前节点标记为B

                        board[x, y] = 'B';

                        foreach (var l in list)

                        {

                            Q.Enqueue(l);

                        }

                    }

                    else

                    {

                        char ct = (char)(minecount + '');//int转ascii码

                        board[x, y] = ct;

                    }

                }

            }

            return board;

        }

    }