【LeetCode】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.

题意：判断数独表中的数字是否违反规则

遍历表，每遍历到一个位置，判断此位置中的数字在对应的行 ，列，单元集合中是否已经存在，已经存在的话返回False

class Solution(object):
    def isValidSudoku(self, board):
        """
        :type board: List[List[str]]
        :rtype: bool
        """
        flag = [set() for i in range(27)]
        for i in range(9):
            for j in range(9):
                if board[i][j] != '.':
                    if board[i][j] not in flag[i]:
                        flag[i].add(board[i][j])
                    else: return False
                    
                    if board[i][j] not in flag[j+9]:
                        flag[j+9].add(board[i][j])
                    else: return False
                    
                    r = i/3
                    c = j/3
                    n = r*3+c
                    if board[i][j] not in flag[n+18]:
                        flag[n+18].add(board[i][j])
                    else: return False
                    
                else: pass
        return True