Sudoku solver @LeetCode

 Not elegant at all, but readable sudoku solver.

https://leetcode.com/problems/sudoku-solver/

class Solution(object):

    

    def checkNew(self, i,j,k,board):

        

        for jj in range(9):

            if board[i][jj] == str(k):

                return False

        for ii in range(9):

            if board[ii][j] == str(k):

                return False

        

        iB = i//3

        jB = j//3

        b = []

        for ii in range(3):

            for jj in range(3):

                if board[3*iB+ii][3*jB+jj] == str(k):

                    return False

        

        

        return True

    

    def backtrack(self, board):

# Find a blank element. The search direction does not a matter,

# but row-oriented here.

        for i in range(9):

            for j in range(9):

                if board[i][j] == ".":

# If blank, try numbers from 1 to 9

                    for k in range(9):

                        if self.checkNew(i,j,k+1,board): # Check if k is OK            

                            board[i][j]=str(k+1)

                            if self.backtrack(board): # Try next blank until OK

                                return True

                            else:

                                board[i][j] = "." # if inconsistent, step back

                    else:

                        return False

        return True

    

    

    def solveSudoku(self, board):

        """

        :type board: List[List[str]]

        :rtype: None Do not return anything, modify board in-place instead.

        """

        self.backtrack(board)