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
1 class Solution(object): 2 def isValidSudoku(self, board): 3 """ 4 :type board: List[List[str]] 5 :rtype: bool 6 """ 7 flag = [set() for i in range(27)] 8 for i in range(9): 9 for j in range(9): 10 if board[i][j] != '.': 11 if board[i][j] not in flag[i]: 12 flag[i].add(board[i][j]) 13 else: return False 14 15 if board[i][j] not in flag[j+9]: 16 flag[j+9].add(board[i][j]) 17 else: return False 18 19 r = i/3 20 c = j/3 21 n = r*3+c 22 if board[i][j] not in flag[n+18]: 23 flag[n+18].add(board[i][j]) 24 else: return False 25 26 else: pass 27 return True