代码块
```class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        m=len(board)
        n=len(board[0])
        st=set()
        #every row
        for r in range(9): 
            st.clear()
            for l in range(9):
                if board[r][l]!=".":
                    if board[r][l] not in st:
                        st.add( board[r][l])
                    else:
                        return False
                
                        
                        
        #every col
        for l in range(9):
            st.clear()
            for r in range(9):
                if board[r][l]!=".":
                    if board[r][l] not in st:                        st.add(board[r][l])
                    else:
                        return False
                        
                                   
        #9 个小方区              
        for r in range(3):
            a=r*3
            for l in range(3):
                b=l*3
                st.clear()
                for i in range(a,a+3):
                    for j in range(b,b+3):
                
                
                      if board[i][j]!=".":
                        if board[i][j] not in st:                            st.add(board[i][j])
                        
                        else:
                            return False
                    
                            
   
        return True