36 Valid Sudoku
36 Valid Sudoku
Valid Sudoku 
Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
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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:
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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:
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**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:
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**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:** false
**Explanation:** Same as Example 1, except with the **5** in the top left corner being modified to **8**. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
Constraints:
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board.length == 9
board[i].length == 9
board[i][j] is a digit 1-9 or '.'.
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class Solution:
def isValidSudoku(self, board: List[List[str]]) -> bool:
"""
validate row and validate col
"""
for j in board:
s = set()
count = 0
for k in j:
if k != ".":
count += 1
s.add(k)
if count != len(s):
return False
for i in range(len(board)):
s = set()
count = 0
for j in range(len(board)):
if board[j][i] != ".":
count += 1
s.add(board[j][i])
if count != len(s):
return False
for r in [0, 3, 6]:
for c in [0, 3, 6]:
s = set()
count = 0
for i in range(r, r+3):
for j in range(c, c+3):
if board[i][j] != ".":
count += 1
s.add(board[i][j])
if count != len(s):
return False
return True
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