class Solution {
    public char[][] updateBoard(char[][] board, int[] click) {
        int row = click[0];
        int col = click[1];
        if (board[row][col] == 'M') board[row][col] = 'X';  // 踩雷直接返回
        else dfs(board, row, col);
        return board;
    }
    
    private void dfs(char[][] board, int row, int col) {
        if (isOutOfBoundary(board, row, col) || board[row][col] != 'E') return; // 越界或已经遍历过
        int mines = getNumOfMinesAround(board, row, col);
        if (mines == 0) {
            // 周围地雷数量为0，才会递归遍历
            board[row][col] = 'B';
            for (int i = -1; i <= 1; i++) {
                for (int j = -1; j <= 1; j++) {
                    dfs(board, row + i, col + j);
                }
            }
        } else {
            board[row][col] = (char)('0' + mines);
        }
    }
    
    // 获取周围地雷数量
    public int getNumOfMinesAround(char[][] board, int row, int col) {
        int result = 0;
        for (int i = -1; i <= 1; i++) {
            for (int j = -1; j <= 1; j++) {
                if ((i == j && i == 0) || isOutOfBoundary(board, row + i, col + j)) continue;
                if (board[row+i][col+j] == 'M') result++;
            }
        }
        return result;
    }
    
    // 判断是否越界
    public boolean isOutOfBoundary(char[][] board, int row, int col) {
        return row < 0 || row >= board.length || col < 0 || col >= board[0].length;
    }
}

class Solution {
    public char[][] updateBoard(char[][] board, int[] click) {
        int row = click[0];
        int col = click[1]; 
        if (board[row][col] == 'M') {
            // 踩雷直接返回
            board[row][col] = 'X';
            return board;
        }

        Queue<int[]> queue = new LinkedList<>();
        queue.offer(click);
        while (!queue.isEmpty()) {
            click = queue.poll();
            row = click[0];
            col = click[1];
            if (isOutOfBoundary(board, row, col) || board[row][col] != 'E') continue;   // 越界或已经遍历过
            int mines = getNumOfMinesAround(board, row, col);
            if (mines == 0) {
                // 周围地雷数量为0，入队遍历
                board[row][col] = 'B';
                for (int i = -1; i <= 1; i++) {
                    for (int j = -1; j <= 1; j++) {
                        queue.offer(new int[]{row + i, col + j});
                    }
                }
            } else {
                board[row][col] = (char)('0' + mines);
            }    
        }
        return board;
    }
    
    // 获取周围地雷数量
    public int getNumOfMinesAround(char[][] board, int row, int col) {
        int result = 0;
        for (int i = -1; i <= 1; i++) {
            for (int j = -1; j <= 1; j++) {
                if ((i == j && i == 0) || isOutOfBoundary(board, row + i, col + j)) continue;
                if (board[row+i][col+j] == 'M') result++;
            }
        }
        return result;
    }
    
    // 判断是否越界
    public boolean isOutOfBoundary(char[][] board, int row, int col) {
        return row < 0 || row >= board.length || col < 0 || col >= board[0].length;
    }
}