Sudoku Solver
Simple
English

Sudoku is a logic-based number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row and each 3×3 sub-grid contains all of the digits from 1 to 9. The puzzle creator provides a partially completed grid, which typically has a unique solution.

For example, the following grid

gives the result:

gives the result:

A puzzle is represented as a list of lists with digits. A zero value means that the value hasn't been set.

Input: The initial 9x9 grid composed by integers as a list of lists.

Output: The result of the sudoku as a list of lists.

Example:

```    checkio([[5, 0, 0, 7, 1, 9, 0, 0, 4],
[0, 0, 1, 0, 3, 0, 5, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 8, 5, 9, 7, 2, 6, 4, 0],
[0, 0, 0, 6, 0, 1, 0, 0, 0],
[0, 2, 6, 3, 8, 5, 9, 1, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 3, 0, 5, 0, 2, 0, 0],
[8, 0, 0, 4, 9, 7, 0, 0, 6]]) == [[5, 6, 8, 7, 1, 9, 3, 2, 4],
[9, 7, 1, 2, 3, 4, 5, 6, 8],
[2, 3, 4, 5, 6, 8, 7, 9, 1],
[1, 8, 5, 9, 7, 2, 6, 4, 3],
[3, 9, 7, 6, 4, 1, 8, 5, 2],
[4, 2, 6, 3, 8, 5, 9, 1, 7],
[6, 1, 9, 8, 2, 3, 4, 7, 5],
[7, 4, 3, 1, 5, 6, 2, 8, 9],
[8, 5, 2, 4, 9, 7, 1, 3, 6]]
```

How it is used: This is a classic constraint satisfaction problem. CSPs are mathematical problems defined as a set of objects whose state must satisfy a number of constraints or limitations. CSPs are the subject of intense research in both artificial intelligence and operations research, since the regularity in their formulation provides a common basis to analyze and solve problems of many unrelated families.
And of course now you can use this code to help your gramma solve all of the puzzles.

Precondition: Each test case has only one unique solution.
∀ x ∈ puzzle : 0 ≤ x < 10

Settings
Code:
CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

`pip3 install checkio_client`

`checkio --domain=py config --key=`

Sync solutions into your local folder

`checkio sync`

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

`checkio serv -d`

Alternatevly, you can install Chrome extension or FF addon

`checkio install-plugin`
`checkio install-plugin --ff`
`checkio install-plugin --chromium`

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

Sync...