477.被圍繞的區域

給一個二維的矩陣，包含'X'和'O', 找到所有被'X'圍繞的區域，並用'X'替換其中所有的'O'。

樣例

樣例 1:

輸入:
  X X X X
  X O O X
  X X O X
  X O X X
輸出: 
  X X X X
  X X X X
  X X X X
  X O X X

樣例 2:

輸入: 
  X X X X
  X O O X
  X O O X
  X O X X
輸出: 
  X X X X
  X O O X
  X O O X
  X O X X

DFS + 邊界尋找 O 替換 T

O替換X，T替換O

class Solution:
    """
    @param: board: board a 2D board containing 'X' and 'O'
    @return: nothing
    """
    def surroundedRegions(self, board):
        # write your code here
        if not board: return


        #初始化
        n, m = len(board), len(board[0])

        def dfs(x, y):
            
 
if (x < 0 or x > n - 1 or y < 0 or y > m - 1):
                return
            
            if board[x][y] == 'O':
                board[x][y] = 'T'
            
                dfs(x - 1, y)
                dfs(x + 1, y)
                dfs(x, y - 1)
                dfs(x, y + 1)


        #找尋邊界，如果滿足邊界 and 為0，則dfs找到上下左右的，換T
        #此時j為0和m 
 
- 1
        for i in range(n):
            if (board[i][0] == 'O'):
                dfs(i, 0)
            if (board[i][m - 1] == 'O'):
                dfs(i, m - 1)
        
        for j in range(m):
            if (board[0][j] == 'O'):
                dfs(0, j)
            if (board[n - 1][j] == 'O'):
                dfs(n - 1, j)
            
        
        #然後迴圈m和n，依次將O轉換為X，並且T轉換為O
        for i in range(n):
            for j in range(m):
                if (board[i][j] == 'O'):
                    #board[i] = board[i].replace(board[i][j], 'X', 1)
                    board[i][j] = 'X'
                elif (board[i][j] == 'T'):
                    board[i][j] = 'O'
                    #board[i] = board[i].replace(board[i][j], 'O', 1)

        return board