Solve Sudoku puzzles - even the toughest !

See and understand the methods and techniques that can be used to solve Sudoku puzzles.

Sudoku puzzles are extremely popular and widely available, and there are many guides to the various methods used to solve them. Do you ever wish that you could see your selected Sudoku being solved before your eyes, step by step, using these techniques from the simplest right through to the most complex?
"Sudoku Lens" is a home-grown program that allows you to do exactly that!

The program runs on Windows computers and allows input of any standard Sudoku puzzle before taking you through the various techniques used when solving these puzzles, displaying exactly what logic it has used or patterns it has discovered in the chosen Sudoku and how each one contributes toward the final solution.
The program is capable of solving any Sudoku puzzle and has options to save a puzzle at various stages of completion, from initial input to the final solution.   A description of the methods and techniques used, with actual examples, is included in the program's main menu.

Methods and Techniques

The solving techniques are grouped into 9 levels, ranging from simple elimination using basic logic and easily recognisable patterns to more complex patterns and deductions. Most "tough" puzzles in popular publications can be solved using just a few of the least complex techniques but occasionally need a specific higher level pattern to break through when no further progress can be made.
The techniques included are Basic Elimination, Box Restrictions, Identical Twins, Triplets and Quadruplets, etc., Hidden Twins & Triplets, Exposed and Hidden Trios, X-Wings, Skyscrapers, Swordfish, and (finally) Forced Values.
In the highly unlikely event of no solution being found using these techniques the program can also move on to a Trial level - where each remaining "possible" digit is tested back through all levels to see whether choosing it would yield a solution. This can result in multiple "solutions" - a true Sudoku only has one - but virtually all examples requiring this technique result from a typo in the original puzzle entry! A puzzle that is often cited as the "World's most difficult Sudoku" does require the program to use this Trial technique to solve it.

In normal operation the program will display every instance it finds (logical deduction or pattern) within each level before moving onto the next, but behind the scenes whenever it finds an improvement in a solution (i.e. eliminating one or more "possibles") it reprocesses the puzzle back through the earlier levels to see whether any further improvements can now be made using the more basic levels before resuming the current level of analysis. Improvements made during these iterations can also be displayed if required for clarification.

The Program

Sudoku Lens was written for fun and is free.  It was written in Basic language and compiled within QB64, but please note that it does not have facilities for mouse control - the keyboard is used throughout, mainly using single key input for selection of options.   The program does not contain any viruses, spyware, internet links or malicious software.

Click on the link below to download the Sudoku Lens zip file and place it into a suitable folder - an example folder might be "Puzzles" - then use Windows to unzip it into the two files "Sudoku_Lens.exe" (the program) and "Sudoku_Lens.dsc" (the description and examples file).  Finally, double-click on Sudoku_Lens.exe to start the program.

To download (1,275,844 bytes)   Click here