PCDB SuDoku Solver
This is an app which solves, or helps you to solve, Killer SuDoku and SuDoku games as published in The Times and elsewhere.
An Android-based version is now available via the Google Play (previously the Android Market) website.
An Android-based version is now available via the Google Play (previously the Android Market) website.
- PCDB SuDoku Lite is a free app which enables you to define and then solve, or get the app to solve a Killer SuDoku or SuDoku game
- PCDB SuDoku Solver is a paid-for app (at a very reasonable price) which in addition enables you to save and restore a Killer SuDoku or SuDoku game, then either get the app to solve it or solve it yourself with the aid of data provided by the app. It also provides a number of solving tools, such as calculating Innies and Outies, which are not available except by manual labour in the Lite version
Both versions are designed to run on Android tablet devices, with a minimum screen size of 1024 x 600 (typically found on a 7" screen), the ability to run apps in Landscape mode, and running Android 3.2 ("Honeycomb") or later.
Note that this app doesn't have a store of SuDoku or Killer SuDoku games (though that's a possible later addition). It's designed just to let you enter the description of a game you've found in a newspaper or book or on-line, in as simple a way as possible, and find a solution to it, and with the full version to do this over and over again or let your friends or children solve the same game against the clock and each other.
If you have an Android tablet device with a screen size of 7" or greater, click on the button here...
The App Screen
This is the PCDB SuDoku Solver app screen. It shows the basic 9 x 9 grid common to both SuDoku and Killer SuDoku, a number of display areas and command buttons, and a number pad.
The command buttons enable you to define a new SuDoku game, define a new Killer SuDoku game, or load a game you've saved previously (only in the Pro version).
The number pad buttons at the bottom right of the screen allow you to enter Killer SuDoku sums when defining a game, or the initial values in a new SuDoku game, or specify the values or candidates for any cell while solving a game of either type. They can also be used to highlight all the cells that contain a particular value as a remaining candidate.
The top gray area at the left is used in Killer SuDoku games and shows all the groups that form part of the definition of the game, as well as any added while solving it.
The bottom large gray area at the left shows the workings (either yours or the apps) while solving a game
The command buttons enable you to define a new SuDoku game, define a new Killer SuDoku game, or load a game you've saved previously (only in the Pro version).
The number pad buttons at the bottom right of the screen allow you to enter Killer SuDoku sums when defining a game, or the initial values in a new SuDoku game, or specify the values or candidates for any cell while solving a game of either type. They can also be used to highlight all the cells that contain a particular value as a remaining candidate.
The top gray area at the left is used in Killer SuDoku games and shows all the groups that form part of the definition of the game, as well as any added while solving it.
The bottom large gray area at the left shows the workings (either yours or the apps) while solving a game
This screen is designed for right-handed users. A variant, with the left and right columns swapped, is obtained by clicking on a Menu option button and then reloading the app.
Defining a Killer SuDoku Game
This screen shows an example of defining a Killer SuDoku game. You touch o drag your finger or stylus over a set of cells that are to form a contiguous group, and then use the number pad to specify the sum for that group. Then start to select the next group, which "fixes" the previous one. Here, most of the groups in the first four rows are defined, and a new three-cell group is shwon highlighted in light red.
You can go back and change the composition or sum of a group if needed, for example if you make an error while defining a game.
Once you have defined a game, you can save it for future use.
You can go back and change the composition or sum of a group if needed, for example if you make an error while defining a game.
Once you have defined a game, you can save it for future use.
Playing a Killer SuDoku Game
When you try to solve a Killer SuDoku game, a number of tools are made available on the command buttons. These include some that you can invoke after selecting a house or set of houses (Find Innies and Outies), and some that need a group to be selected (Group Options, Split Group). As the game progresses some cells are reduced to just a single candidate each, and these are shown in red. If you touch one of these red numbers, the value is confirmed in the cell and any other instance of that value in the same row, column, box or any group that the cell belongs to is eliminated. The value in the cell is then displayed in blue.
The screen shot shows the properties for the groups in the game, and the recent progress of the solving techniques.
The screen shot shows the properties for the groups in the game, and the recent progress of the solving techniques.
Playing a SuDoku Game
A SuDoku game is defined by touching each cell for which you are given a value, and then touching the relevant number pad button.
Playing a SuDoku game works in much the same way. You touch a cell and then touch the value to go into it, once you've worked that out. However, there are two useful features that help you decide what that value should be.
First, all the remaining candidates for the cell are shown in small numbers at the bottom of the cell. If you work out that you can eliminate one or more of these candidates in one or more cells, touch the cell(s) and enter the remaining candidates (e.g. 235) and then "OK". Alternatively, touch "¬" followed by the candidates you want to exclude (again followed by "OK"). You can select several cells and apply the same elimination to all of them.
Secondly, if no cells are selected, touching any number pad key will highlight all the cells for which that numer is still a possible candidate. Here, the "5" button has been touched and all the cells that contain 5 as a candidate are highlighted in a pastel shade of blue. (The colours used vary according to the number button touched.) This display can provide useful visual clues to the existence, for example, of singlets or forcing chains. In this example, it's clear that the 5 in Box 6 must go in Cell (5,8), and also clear that once you've set that up another 5 goes in Cell (4,3) and then (8,2).
Playing a SuDoku game works in much the same way. You touch a cell and then touch the value to go into it, once you've worked that out. However, there are two useful features that help you decide what that value should be.
First, all the remaining candidates for the cell are shown in small numbers at the bottom of the cell. If you work out that you can eliminate one or more of these candidates in one or more cells, touch the cell(s) and enter the remaining candidates (e.g. 235) and then "OK". Alternatively, touch "¬" followed by the candidates you want to exclude (again followed by "OK"). You can select several cells and apply the same elimination to all of them.
Secondly, if no cells are selected, touching any number pad key will highlight all the cells for which that numer is still a possible candidate. Here, the "5" button has been touched and all the cells that contain 5 as a candidate are highlighted in a pastel shade of blue. (The colours used vary according to the number button touched.) This display can provide useful visual clues to the existence, for example, of singlets or forcing chains. In this example, it's clear that the 5 in Box 6 must go in Cell (5,8), and also clear that once you've set that up another 5 goes in Cell (4,3) and then (8,2).
User Guide
The app contains a comprehensive help file which you can display by touching the "Help" menu item on the Action Bar. In addition, there is an equally comprehensive User Guide which you can download here.
Well-Formed Games
PCDB SuDoku Solver uses strict logic to solve both Killer SuDoku an SuDoku games. Thus, it can only solve games that have just a single valid solution. These are called Well-Formed Games. Some games (not those in The Times) have multiple solutions. And there are some SuDoku solving apps that use a brute force approach, and (more subtly) a Japanese technique called Nishio which is, essentially, trial-and-error under another name. We don't use either of those techniques.
More Information on Killer SuDoku
A number of sources provide examples of Killer SuDoku games.
Times Newpapers has published games daily in The Times and Sunday Times since 2005, and was responsible for the name Killer SuDoku on the grounds that the original Japanese name, Samunanpure, was unpronouncable in English. (They may be right. An alternative I've discovered is Sum-SuDoku.) Their games are provided by Puzzler Media. Note that on-line versions of these newspapers are behind a paywall.
Puzzler Media provide the games used by The Times and Sunday Times.
killersudokuonline.com publishes daily games of varying degrees of difficluty, and a weekly "Mind Bending" game. Loth as we are to admit it, PCDD SuDoku Solver can't as yet solve all of the published Mind Bending games.
A number of websites provide useful information on solving techniques. Most of those you will find described have been implemented in the algorithms used by PCDB SuDoku Solver.
In 2006/7, Canadian music reviewer Nate Dorward published a number of extremely challenging Killer SuDoku games, and some blogs that showed how to solve them using a wide variety of often complex techniques. All those techniques have been incorporated into the algorithms used by PCDB SuDoku Solver, and the app can solve all the games that Nat published. Regrettably, Nate no longer blogs on this subject and his illuminating blogs appeat to be no longer available on-line
killersudokuonline.com publish a number of "how to" articles for some of their games, including "Mind Bending" number 24.
Puzzler Media, as well as publishing daily games, maintain an on-line encyclopaedia of information about ppuzzles, including Killer SuDoku (though they prefer the name Samunanpure).
More Information on SuDoku
A rather larger number of sources, including many national and regional newspapers, provide examples of SuDoku games. Those known to us include the following.
Times Newspapers publish daily games in The Times and Sunday TImes. These are provided by Puzzler Media. Note that the on-line versions of these newspapers are behind a paywall. Almost all games printed in The Times have been tested on PCDB SuDoku Solver, and all those tried have been solved by it.
Puzzler Media provide the games used by The Times and SundayTImes
Sudopedia provides a wealth of sometimes esoteric information about the mathematical theory and practice of SuDoku, and of its many variants. If you want to know how many possible games there are, or what is the smallest number of fixed cells needed to define a solvable game, this is the place to go. It mentions Killer SuDoku but doesn't yet provide much information about it.
There are many sources of information on solving techniques for SuDoku. Google "SuDoku".
