[Leetcode][python]Surrounded Regions/被围绕的区域

class Solution(object):
    def solve(self, board):
        """
        :type board: List[List[str]]
        :rtype: void Do not return anything, modify board in-place instead.
        """
        if not board or not board[0]:
            return
        n = len(board)
        m = len(board[0])
        queue = []
        # 保存所有位于边缘的O
        for i in range(n):
            for j in range(m):
                if ((i in (0, n - 1)) or (j in (0, m - 1))) and board[i][j] == 'O':  # i in (0, n - 1) 最上面和最下面两排
                    queue.append((i, j))
                    print (i,j)
        # 保存所有与边缘O相连的O
        while queue:
            r, c = queue.pop(0)  # i, j = r, c
            if 0 <= r < n and 0 <= c < m and board[r][c] == 'O':
                board[r][c] = 'M'  # 变为M的则是不需要变成X的
                if r - 1 >= 0 and board[r - 1][c] == 'O':
                    queue.append((r - 1, c))
                if r + 1 < n and board[r + 1][c] == 'O':
                    queue.append((r + 1, c))
                if c - 1 >= 0 and board[r][c - 1] == 'O':
                    queue.append((r, c - 1))
                if c + 1 < m and board[r][c + 1] == 'O':
                    queue.append((r, c + 1))
        # 重新更新棋盘
        for i in range(n):
            for j in range(m):
                if board[i][j] == 'M':
                    board[i][j] = 'O'
                else:
                    board[i][j] = 'X'