## Question

Determine if a `9 x 9`

Sudoku board is valid. Only the filled cells need to be validated **according to the following rules**:

- Each row must contain the digits
`1-9`

without repetition. - Each column must contain the digits
`1-9`

without repetition. - Each of the nine
`3 x 3`

sub-boxes of the grid must contain the digits`1-9`

without repetition.

**Note:**

- A Sudoku board (partially filled) could be valid but is not necessarily solvable.
- Only the filled cells need to be validated according to the mentioned rules.

**Example 1:**

Input:board = [["5","3",".",".","7",".",".",".","."] ,["6",".",".","1","9","5",".",".","."] ,[".","9","8",".",".",".",".","6","."] ,["8",".",".",".","6",".",".",".","3"] ,["4",".",".","8",".","3",".",".","1"] ,["7",".",".",".","2",".",".",".","6"] ,[".","6",".",".",".",".","2","8","."] ,[".",".",".","4","1","9",".",".","5"] ,[".",".",".",".","8",".",".","7","9"]]Output:true

**Example 2:**

Input:board = [["8","3",".",".","7",".",".",".","."] ,["6",".",".","1","9","5",".",".","."] ,[".","9","8",".",".",".",".","6","."] ,["8",".",".",".","6",".",".",".","3"] ,["4",".",".","8",".","3",".",".","1"] ,["7",".",".",".","2",".",".",".","6"] ,[".","6",".",".",".",".","2","8","."] ,[".",".",".","4","1","9",".",".","5"] ,[".",".",".",".","8",".",".","7","9"]]Output:falseExplanation:Same as Example 1, except with the5in the top left corner being modified to8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.

**Constraints:**

`board.length == 9`

`board[i].length == 9`

`board[i][j]`

is a digit`1-9`

or`'.'`

.

## Python Solution

class Solution: def isValidSudoku(self, board: List[List[str]]) -> bool: d = set() for i in range(9): for j in range(9): if board[i][j]=='.': pass elif ((str(board[i][j]) + ' r ' + str(i)) not in d) and ((str(board[i][j]) + ' c ' + str(j)) not in d) and ((str(board[i][j]) + ' b ' + str(i//3)+str(j//3)) not in d): d.add(str(board[i][j]) + ' r ' + str(i)) d.add(str(board[i][j]) + ' c ' + str(j)) d.add(str(board[i][j]) + ' b ' + str(i//3)+str(j//3)) else: return (False) return True