Optimised Solver for Sudoku

[potatochick2020]

    By looking at the code of the sudoku class, there are two parts generator and a solver.

I propose that we make TWO separate issues for each one, and add a generator with specific difficulty.

Regarding the solver, there are better algorithms than Backtracking, I have two candidates in my mind Dancing Links algorithm and the Rule-based Algorithm, both of them are faster than the backtracking.

This Medium article explains and Implements the Dancing Links Algorithm, and this Paper explains the Rule-based algorithm.

By looking at the two proposed algorithms it would take time to read the papers and deciding wich one to implement and as I'm still a student contributing on my weekend so, I'll do my best to make the pull request by the end of friday.

If there's another algorithm in your mind please let me know.

Originally posted by @MMostafa-Hub in #3 (comment)

[potatochick2020]

@MMostafa-Hub I am a student too, this is a really good thing that you could observe there is a part of optimised solution.

You could decide which algorithm to use.

[MMostafa-Hub]

For the time being, I don't have the time to read both articles with attention to detail and decide which one to use, but It will be done on Friday.
so by Friday, I'll implement

1. new SudokuSolution()
2. try to optimize isValid(), isPlacable(), isComplete()

Is this ok with you?

[potatochick2020]

Sorry for my late reply.
Sure, let's say next Monday? No rush at all.

[MMostafa-Hub]

Ok, the pull request will be ready on Monday

[MMostafa-Hub]

Can I get assigned to the issue, so that i can start working on it?