[Leetcode]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.

判断当前数独是否合法~对每一行，每一列，还有每个九宫格进行验证，判断是否存在重复元素~注意判断九宫格时循环的写法~

class Solution:    # @param board, a 9x9 2D array    # @return a boolean    def isValidSudoku(self, board):        if board is None or len(board) != 9 or len(board[0]) != 9: return False        for row in board:            dup = []            for i in row:                if i != '.':                    if i not in dup:                        dup.append(i)                    else:                        return False        for j in xrange(9):            dup = []            for i in xrange(9):                if board[i][j] != '.':                    if board[i][j] not in dup:                        dup.append(board[i][j])                    else:                        return False        for k in xrange(9):            dup = []            for i in xrange(k/3*3, k/3*3 + 3):                for j in xrange(k%3*3, k%3*3 + 3):                    if board[i][j] != '.':                        if board[i][j] not in dup:                            dup.append(board[i][j])                        else:                            return False        return True