36. Valid Sudoku
Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.
The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
A partially filled sudoku which is valid.
Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
Solution: HashSet
class Solution(object):
def isValidSudoku(self, board):
"""
:type board: List[List[str]]
:rtype: bool
"""
seen = set()
for row in xrange(9):
for col in xrange(9):
num = board[row][col]
if num == '.':
continue
for val in (row, -1, num), (-1, col, num), (row / 3, col / 3, num):
if val in seen:
return False
seen.add(val)
return True