# Sudoku

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## Contents

### About

There is very little to tell about this program. It is just an attempt to make a program which solves Sudoku puzzles.

### License

See the sources. I just hope it is a useful demo. Useful as in you can learn something from it.

### Author

Matthijs Willemstein

Modifications by Bart

### Download

The sources can be found at the Lazarus-CCR repository and can be obtained via svn:

svn co https://svn.code.sf.net/p/lazarus-ccr/svn/applications/sudoku/ local/path/to/sudoku

Alternatively you can view the sources through viewcv:

https://sourceforge.net/p/lazarus-ccr/svn/HEAD/tree/applications/sudoku/

### Usage

If you run the program you will see a grid, and two buttons. If you press the "Edit" button, you are able to edit the grid and place the numbers in the grid according to your puzzle.

If you press the "Clean" button, the grid will be cleared.

When you are finished entering the digits press "Solve" and the grid will be filled with the solution.

If the program is unable to completely solve the Sudoku, a ScracthPad form will pop up.

This form shows for each cell what possible options are left.

Solved cells will contain a single number, unsolved will have a range of possibilities, shown as commaseparated values enclosed in brackets (e.g. "[1,4,8]").

You can edit the grid and copy the values back to the main form, then try to solve it again.

(Note: only cells that contain a single digit will be copied back to the main form.)

The program alos has the option to load and save sudoku files.

A sample sudoku file is incuded in the svn repository.
The file format is a simple textfile, it is explained in the sources.

#### Example for using the ScratchPad functionality

The sample file unsolvable.sudoku (included in the repository) cannot be solve by the program.

If you load it and then click Solve, the ScratchPad will pop up.

Now go and change the second cell in the bottom row from "[2,6]" to "2" (without the quotes) and click the "Copy back..." button.

The changes are propagated back to the main form.

Again click the "Solve" button.

The program now **will** be able to solve the Sudoku.

### Description

The programs solves all Sudoku puzzles that can be solved by logic. It will not solve the puzzle where you need to guess for a solution.

So it follows these rules (taken from WebSudoku):

The rules of Sudoku are simple. Enter digits from 1 to 9 into the blank spaces. Every row must contain one of each digit. So must every column, as must every 3x3 square. Each Sudoku has a unique solution that can be reached logically without guessing.

### Related Sites

Sudoku Solver Online Sudoku Solver Released Under The GNU public license.