https://github.com/james-p-d/sudoku

A Sudoku puzzle solver with algorithm in F# and UI in C# Winforms
https://github.com/james-p-d/sudoku

ai csharp fsharp sudoku winforms

Last synced: 18 days ago
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A Sudoku puzzle solver with algorithm in F# and UI in C# Winforms

• Host: GitHub
• URL: https://github.com/james-p-d/sudoku
• Owner: James-P-D
• License: mit
• Created: 2019-11-21T19:46:28.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2021-07-04T20:44:13.000Z (over 3 years ago)
• Last Synced: 2024-11-17T10:36:01.619Z (3 months ago)
• Topics: ai, csharp, fsharp, sudoku, winforms
• Language: C#
• Homepage:
• Size: 325 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Sudoku

A Sudoku puzzle solver with algorithm in F# and UI in C# Winforms

![Screenshot](https://github.com/James-P-D/Sudoku/blob/master/Screenshot.gif)

## Method

Most Sudoku solvers I came across simply chose to implement [Peter Norvig's method](https://norvig.com/sudoku.html), but I decided I'd rather use the same method I use when solving the puzzle with pen-and-paper.

### Easy Cells

The easiest step for finding the value for a particular cell, is to find an empty cell and then figure out what it *can't* be.

For example, lets consider the following board taken from the [Guardian Easy Sudoku #4,612 from Mon 18 Nov, 2019](https://www.theguardian.com/lifeandstyle/2019/nov/18/sudoku-4612-easy).

![Easy Cells Screenshot](https://github.com/James-P-D/Sudoku/blob/master/Easy.png)

In the above initial board, concentrate on the 9x9 square in the middle-left of the board, and in this square, look at the cell in the very centre.  

We can instantly tell that value of this cell can't be `3 or 5` because of other values in the 9x9 square. We can also tell that is can't be `1, 3 or 6` because of other cells in the same column. Finally, from analysing the values in the rest of the row we can also tell that it can't be `2, 3, 7, 8, or 9`. Putting all this information together and we know the cell can't be `1, 2, 3, 5, 6, 7, 8 or 9`, and must therefore be `4`.

### Medium Cells

Having found all the easy cells, we find ourselves with the following board:

![Medium Cells Screenshot](https://github.com/James-P-D/Sudoku/blob/master/Medium.png)

There are no more easy solutions to be found, but let's consider the central 9x9 square.  

This 9x9 square is missing the numbers `4, 5 and 6`. The numbers `4 and 5` could conceivably go in any of three available cells, but the number `6` *cannot* be on the top row because of the other `6` in the 9x9 square to the right. Therefore the `6` *must* be in the empty cell on the bottom row of the 3x3 square.

### Hard Cells

Brute force. Still to be implemented.