被围绕的区域

from operator import le
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param board char字符型二维数组 
# @return char字符型二维数组
#
class Solution:
    def surroundedArea(self , board: List[List[str]]) -> List[List[str]]:
        # write code here
        width = len(board[0])
        height = len(board)

        m = [[0 for i in range(width)] for j in range(height)]

        next_group = 1
        res_gourp = set()

        for i in range(len(board)):
            for j in range(len(board[0])):
                if board[i][j] == 'X':
                    continue

                # 已经被标记组别
                if m[i][j] < next_group and m[i][j] != 0:
                    continue
                else:
                    res_gourp.add(next_group)
                    # 开始使用dfs标记组别
                    self.dfs(board, i, j, next_group, m)
                    next_group += 1
        
        # 绕圈一周
        for i in range(width):
            if m[0][i] in res_gourp:
                res_gourp.remove(m[0][i])

        for i in range(height):
            if m[i][0] in res_gourp:
                res_gourp.remove(m[i][0])

        for i in range(width):
            if m[height-1][i] in res_gourp:
                res_gourp.remove(m[height-1][i])

        for i in range(height):
            if m[i][width-1] in res_gourp:
                res_gourp.remove(m[i][width-1])

        for i in range(len(board)):
            for j in range(len(board[0])):
                if m[i][j] in res_gourp:
                    board[i][j] = 'X'

        return board

    def dfs(self, board, x,y, now_group, m):
        if board[x][y] == 'X':
            return
        if m[x][y] == now_group:
            return
        m[x][y] = now_group

        if x > 1:
            self.dfs(board, x-1,y,now_group,m)

        if y > 1:
            self.dfs(board, x,y-1,now_group,m)

        if x < len(m) - 1:
            self.dfs(board, x + 1,y,now_group,m)

        if y < len(m[0]) - 1:
            self.dfs(board, x,y + 1,now_group,m)