A Brief Introduction To YZF_Sudoku
YZF_Sudoku is a Sudoku solver. It is a Sudoku creator. It is a Sudoku Solving Assistant. It can be used by people just beginning with Sudoku and it can be used, to advantage, by Sudoku experts as well.
Some Background
YZF_Sudoku is written by Yang Zhi Feng [ Yang, YZF or his forum name : yzfwsf ] . This project is ongoing and the solver is constantly being enhanced and improved. The user interface [ UI ] for YZF_Sudoku is modelled after HoDoKu [ by Bernhard Hobiger ] but YZF_Sudoku has been developed from the ground up using Free Basic within the MS Windows XP operating system [ OS ]. The last release of HoDoKu was in 2012 and Bernhard passed away several years ago. HoDoKu remains very fine software but it is now far from up to date. The Sudoku community continues to grow the techniques used to solve Sudoku puzzles. Many of these new methods are not included with HoDoKu. YZF_Sudoku contains a majority of the techniques in HoDoKu but YZF_Sudoku now contains a very long list of the new techniques and with every new release there are changes and additions implemented.
Finding, Downloading, Installing and Launching the Latest Release of YZF_Sudoku
YZF_Sudoku is to be found at Yang's Google Drive :
drive.google.com/drive/folders/1uk4CCzW2fabLCawCwpwsQga2LtniXLQo
Go to this site and move to the bottom of the page. There you will see the most recent release of YZF_Sudoku as a .7z file. 7z is an archiving program. If you do not have this program, you can find it on the net and it is safe to download using :
https://www.7-zip.org/download.htmlThe archive contains four files. After unzipping these files using 7-zip, keep these four files in a folder.
If your OS is MS Windows, you should be able to run the YZF_Sudoku.exe file directly. You should see a window with a puzzle on the left side and an initially blank right side. You will see five drop-downs on the top left of the window and three tabs on the right hand side. At the bottom, there is an unnamed 'Explanation' window.
If your OS is Linux, you will need additional software to run YZF_Sudoku. The best option here is the Wine software at :
https://www.winehq.org/After installing Wine, you should be able to right click on the .exe file to obtain the option to launch YZF_Sudoku using Wine.
Then, you should see then a window quite similar to the window with the Windows OS.
If your OS is Mac, success with Wine to run YZF_Sudoku appears to be dependent on the version of your OS. Wine should work quite well with MacOS versions 10.8 to 10.14 to launch YZF_Sudoku. As mentioned at the beginning of this guide, YZF_Sudoku is very much a work in progress.
One may get crashes or unexpected responses from time to time. No need to be alarmed with such events. Maybe you will need to 'Force-Quit' and relaunch. Not a big deal.
There are alternatives to Wine that could be explored for the more recent versions of the MacOS.
Orientation to YZF_Sudoku
The solver has a main menu bar with File, Edit, Options, Tool and Help as 'drop-downs'. You can explore the various options with each of these drop-downs. There is quite a bit of content here. It is best to proceed gradually as you learn how YZF_Sudoku works.
Inputting a Puzzle
Perhaps you have been trying Sudoku puzzles from your local newspaper. The most basic way to see such puzzles in YZF_Sudoku is to enter them using the 'New Givens' tool. You can find 'New Givens' in the File drop-down.
After clicking on 'New Givens', you will see each of the 81 cells initially containing all 9 digits called the candidates. With your mouse, you can click on a digit to enter a given in that cell. You start with these givens as shown in your newspaper. There will be 17 or more givens. After you have entered each of the givens, you can click 'Play Game' from the File drop-down.
YZF_Sudoku will then show you the entered givens and it will show you the candidates in each of the remaining cells after applying the rules of Sudoku. The candidates appear as small numbers: 1,2 3 along the top, 4,5,6 along the middle and 7,8,9 along the bottom. Notice that the position determines the number. This so-called 'key-pad' notation for the candidates in a cell is the most widely seen. There are a number of other notations out there. If you would rather not see the candidates, you can toggle with 'Show Candidates' in the Options drop-down.
Solving your puzzle
Now you can begin to solve the puzzle. As you identify a solved cell, you either click on that candidate [ if 'Show Candidates' is on ] or your type the digit after positioning your mouse over the cell [ if 'Show Candidates' is off ]. The solved cells are shown in blue while the givens remain black.
Let us suppose that you have solved some of the cells but you are now stuck. First, make sure that 'Show Candidates' is on. Then, you can request a possible next step using 'Show Next Step' from the Tool drop-down.
The step will show the excluded candidates in red. There may be a quite elaborate visual showing the intricacies of the step. You can exclude candidates by right clicking the appropriate digits. Or you can let YZF_Sudoku do these exclusions for you by repeating 'Show Next Step'. YZF_Sudoku gives you a brief explanation of each step in the bottom 'Results' window. Notice that < > means 'not equal' or 'excluded' or 'eliminated'.
Let us now explore the right hand window in YZF_Sudoku. If you can use 'Auto Solve' from the Tools drop-down.
In the 'Solution Path' window, we will see an entire path to the solution of the entered puzzle. Techniques with a white background are considered 'Easy' steps while those techniques with a Green background are considered 'Medium'.
YZF_Sudoku assigns techniques with five different levels of difficulty : Easy, Medium, Hard using a yellow background, Unfair using an orange background and Extreme using a red background. Further, YZF_Sudoku assigns a level of difficulty for the puzzle as a whole. This level is displayed in the lower left corner of the main window along with a numerical score based on a variant of another solver called Sudoku Explainer [ SE ].
YZF_Sudoku assigns the very hardest puzzles an 'Insane' level based on the SE variant.
Thresholds for these levels have defaults set with the install of YZF_Sudoku. One can personalize these settings by making changes to the .ini file that comes with YZF_Sudoku.
With each step, one receives a brief explanation in the bottom 'Results' window. The visual of the step in the grid is often very helpful to learning how the step works. YZF_Sudoku uses names for the steps that are quite standard in the Sudoku literature and so you can often do an internet search to get more detailed explanations. The original HoDoKu site has quite detailed explanations:
http://hodoku.sourceforge.net/en/index.phpFor levels of Unfair and Extreme, many of the steps are based on a class of methods called chains. The notation for such chains used by YZF_Sudoku is based around the 'Eureka' notation. Eureka is becoming quite standard now and has all but replaced the notation used in HoDoKu. You can search on Eureka notation for the details.
The sudopedia site is a good place for a wide range of Sudoku matters:
http://sudopedia.enjoysudoku.com/The sudopedia site was last modified in July of 2010. In the intervening years, there has been a number of important new techniques developed by the Sudoku community. Searching for detailed explanations of these new techniques can yield helpful results but often the resources are quite advanced and not for the 'faint of heart'.
At any stage in a puzzle path, there will be many possible steps available. You can obtain a list of the possible steps by using 'Find All Steps' from the Tools drop-down. Then, you can click on the 'All Possible Steps' tab.
YZF_Sudoku often identifies a quite long list of possible next steps for this puzzle. You can select specific techniques by using the drop-down on the right hand side of this window. By default, one sees 'All Types' but one can make any specific selection.
The third tab with this window is called 'Color Cell'. Color Cell provides the human solver with all kinds of ways to colour candidates or colour cells, draw arrows between candidates to build chains and otherwise assist the human solver with finding steps with a very wide range of techniques. One can also use the filter displayed just below the main menu to identify bi-value cells, conjugate pairs and much more. These filters are labelled 1 through 9 and ab .
Saving A Puzzle
There are many ways to save a puzzle. If you use 'Copy Givens' from the Edit drop-down, then the puzzle is copied to the clipboard of your computer as an 81 digit string like:
..6.74.5.9..3.6.4.........8......52.49..8..71.17......8.........6.5.7..3.5.46.2..
This format is, by far, the most compact version. You can see that digits are saved first row 1, then row 2 and so on until row 9. One sees dot [ . ] for the cells that do not contain givens. One also sees this format with a zero [ 0 ] instead of a dot. YZF_Sudoku will receive such 81 digit versions of a puzzle from the clipboard using Paste in the Edit drop-down. YZF_Sudoku can receive puzzles in many other formats too. For example, maybe you have your puzzle in a text-like format in the clipboard :
- Code: Select all
123 23 6 | 8 7 4 | 139 5 29
9 278 1258 | 3 125 6 | 17 4 27
12357 2347 12345 | 129 1259 1259 | 13679 1369 8
------------------------+----------------------+---------------------
36 38 38 | 7 1349 139 | 5 2 469
4 9 235 | 26 8 235 | 36 7 1
2356 1 7 | 269 23459 2359 | 34689 3689 469
------------------------+----------------------+---------------------
8 2347 12349 | 129 1239 1239 | 14679 169 5
12 6 1249 | 5 129 7 | 1489 189 3
137 5 139 | 4 6 8 | 2 19 79
Pasting a puzzle with this format is acceptable to YZF_Sudoku.
In addition, you can copy the current state of the puzzle with 'Copy With Cell State'. This format can be pasted back into YZF_Sudoku at another time. This format is quite concentrated like the 81 digit format.
You can also save a puzzle as a .txt file using 'Save Givens'. You will be prompted for a folder location and a file name to save the file.
You can save the currently displayed solution path. Right click on any step in the displayed path and then select 'Copy Solution Path'. This path is then saved to the clipboard.
Creating A Puzzle
YZF_Sudoku has a puzzle generator. First select the level for the desired puzzle. That drop-down is just below the main menu. Then click the icon just to the left of the drop-down. This icon contains the digits 8 9 6 7 with a red plus sign. You will then see your puzzle with the requested level of difficulty.
You can also generate puzzles that will contain specific techniques. You can use 'Batch Generate Puzzles' from the Tool drop-down. You receive a window to enter the details for your desired puzzles. When you are ready, click 'Generate'. The 'Batch' generation will continue until you click 'Cancel'.
