Execute time is fast ( < 1 second )
Easy to understand the code
The method of Recursive.
Function FindRestNumber: Find the available numbers that we can fill to the square. If the Sudoku is invalid, the error will be set to 1.

For ex: if the numbers of row,column and 3x3 is [ 1 4 5 6 ], the result of function is [2 3 7 8 9].

Function SDK: Fill directly the number to the square that has 1 case.
For ex: if B(1,1)=[1 2 3 5 6 7 8 9]-> A(1,1)=4
if B(1,1)=[1 2 3 6 7 8 9] -> A(1,1) cannot be filled.

Function SDK1: If the square now has more than 1 case, it will test for each number until the Sudoku is filled with all numbers.