```
class Solution(object):
def isValidSudoku(self, board):
"""
:type board: List[List[str]]
:rtype: bool
"""
for i in range(9):
for j in range(9):
if board[i][j] == ".":
continue
# in one row
for k in range(j+1, 9):
if board[i][j] == board[i][k]:
return False
# in one col
for k in range(i+1, 9):
if board[i][j] == board[k][j]:
return False
# in one square
for k in range(i+1, (i/3+1)*3):
for h in range(j/3*3, (j/3+1)*3):
if h != j and board[i][j] == board[k][h]:
return False
return True
```