Valid Sudoku

```python
def isValidSudoku(self, board: List[List[str]]) -> bool:
    rows = [set() for i in range(9)]
    cols = [set() for i in range(9)]
    squares = [[set() for i in range(3)] for i in range(3)]

    for i in range(len(board)):
        for j in range(len(board[i])):
            if board[i][j] == ".":
                continue
            if board[i][j] in cols[j]:
                return False
            else:
                cols[j].add(board[i][j])

            if board[i][j] in rows[i]:
                return False
            else:
                rows[i].add(board[i][j])

            if board[i][j] in squares[i // 3][j // 3]:
                return False
            else:
                squares[i // 3][j // 3].add(board[i][j])

    return True
```