leetcode36 Valid Sudoku

"""
Determine if a 9x9 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 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.
A partially filled sudoku which is valid.
The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
Example 1:
Input:
[
  ["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:
[
  ["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.
"""
"""
很考验python功底的一道题
"""
class Solution:
    def isValidSudoku(self, board):
        for num1 in board:
            if not self.isRep(num1):
                return False
        for col in zip(*board):  # ！！！矩阵的转置
            if not self.isRep(col):
                return False
        for i in (0, 3, 6):
            for j in (0, 3, 6):
                square = [board[x][y] for x in range(i, i + 3) for y in range(j, j + 3)]
                if not self.isRep(square):
                    return False
        return True

    def isRep(self, unit):
        unit = [i for i in unit if i != '.']
        return len(set(unit)) == len(unit)  # ！！！判断数组中有无重复值得方法。set