Author Archives: ruud

Crossword Killers

These puzzles have been posted by MikeJapan and h3lix on DJ-Ape’s forum.

They are an interesting variation which combine a zero-killer with crosswords in the empty regions. I adapted SumoCue to handle these puzzles. In “letter” mode, the program shows the placed digits and candidates as letters in the “zero” regions. In stead of cage combinations, there is a new tool that shows all remaining valid words for each region. This tool can be set to “horizontal” and “vertical” mode, because a single cell can belong to 2 words.

I have already implemented a new solving technique that eliminates candidates that do not occur in any valid word. There is a background interface with the Internet Anagram Server at Wordsmith to retrieve all valid words for the given letters. The SumoCue V2 save format can save the letter table.

I’m not sure what techniques to implement next. It’s easy to build the word lists into DLX and verify a unique solution, but it is nicer to have more human executable solving techniques. The next target could be invalid word combinations, where the combination violates the sudoku rule by placing repeating digits in a box. This could lead to words being eliminated from the list, because they cannot be used in any combination, which in turn could cause letter eliminations.

It looks like a pretty far-fetched technique, but it is still logical.

Another technique that I’ve been thinking about is a variation on the killer pair/triple/quad. When a word, when placed, would eliminate all candidates from a cell, or all combinations from a cage, the word cannot be placed. All cells of the cage must “see” the word, so this is not a technique that can be used on a large scale.

I’ll see what comes next.

Sudoku-X, Windoku and Disjoint Groups

These are 3 variations, which I have implemented in the latest version of SudoCue. I still need to build these extra contraints into the DLX solver, so the program can also generate these variations. The human style solver supports and solves each of these variations. A nice opportinity to publish 3 new series of daily puzzles. I’ve already generated a collection of Windokus that would easily fit into the Nightmare category.

Celebrity Killer

This is a one-off puzzle, which I posted on both DJ Ape’s forum and on the forum supporting Mike Mepham’s site. A novel concept. Convert a list of names into cage sums.

I know there are very few people who read this blog, so it is safe to add the full list of names here, including the first names that I refused to post with the original puzzle.

A = Ravi Shankar
B = Lucille Ball
C = Yoko Ono
D = Oskar Schindler
E = John F Kennedy

F = Gene Krupa
G = John Pritchard

H = Lionel Hampton
I = Nelson Mandela
J = John Cage
K = Errol Flynn

L = Jim Lovell
M = Ella Fitzgerald
N = George Patton

O = Joe Shuster
P = Karel Appel
Q = Orson Welles
R = Bruno Kreisky

S = Alec Guinness
T = Niels Bohr
U = Edith Piaf

V = Dizzy Gillespie
W = Maria Callas
X = Edward Teller
Y = Joseph Barbera

If you managed to find this list, good for you!

This concept can be worked out, replacing the names with triva questions that each have the cage sum as the answer. A whole new line of puzzles can be created this way.

Daily Telegraph publishes first HaniDoku

A stunning achievement. Mike Mepham, who has compiled a 4 page puzzle supplement for the Daily Telegraph and the Sunday Telegraph, has included a debut HaniDoku puzzle. Visits to my www.hanidoku.com website have grown to 3 figures, from the usual 10 to 15.

Interesting to see how the feedback will be. This variant is so very promising.

I just calculated the POM space for the variant with interesting results. Only 244 templates exist, but with the optional digits, there can be upto 8 positions in a template that may or may not contain a digit. I cannot yet oversee the full implications of the optional digits on the templates. It could be that there are “incomplete” templates that cannot be expanded to one of the 244 full templates, but which are nevertheless valid for a digit with optional positions. In-depth testing must be done to gain some insight.

The road to Perfection

I have brought 2 releases of SudoCue to the site in a very short period of time. The visible improvements can be seen on the release notes page of the www.sudocue.net website, but the internal restructuring is not seen by the outside world. Here are a few notes on how the architecture has changed.

First, a virtual class named Trick has been added. This class can save itself to the configuration file, has a name, a base score, a sequence number, an optional administration score, several classification flags, tries and usage counters, and a Performed method which reports a successful application of the trick.

A Tricks class contains a collection of Trick instances which can be enumerated.

The user can enable or disable any of these tricks through the options panel, and also change the order in which they are tried.

Several tricks that are basically different sizes of a single technique have a base class that performs the technique, with the size property of the derived class as a parameter. There are 2 tricks which are kept at the end of the collection, the DLX brute force solver and a Surrender class the does nothing, but declares the puzzle unsolvable. This trick cannot be disabled by the user for obvious reasons.

The only thing that I need to add a new technique is define a new class derived from the Trick class and add it initially to the Tricks collection. In earlier versions, I had to change the Log, the Options class, the Options dialog, the main solving method in the Grid class and the Analyzer dialog, even before I could start coding the nitty gritty stuff. This hassle disencouraged me from quickly adding new tricks.

There is also a strict separation between setup and play mode. The solver does nothing in setup mode, but validates and rates the puzzle when you switch to play mode. Earlier, the program had the habit of kicking in too soon, filling the log with complicated tabling chains when all it had to do it wait for all the clues to arrive. With uniqueness, this could even lead to a solving path going the wrong way.

With these changes, the program is ready to be expanded with all the lovely tricks that have been developed in the last months. Some have already been added to the program. More will follow.

Noblesse Oblige

Since Mike Barker has put my solving guide on top of his reference list in the sudoku player’s forum, I receive a lot of traffic from that reference. Thanks to Mike for this fine gesture.

I do not want let let all these new visitors down with a poor solving guide, so I started to rewrite it. The introduction is much longer now, with new topics covering sudoku history, an extended symmetry topic, minimal puzzles, known sudoku controversies and lots of explanation of the terminology. It almost reads like a book.

I replaced all the images, using a white cell background in stead of the typical SudoCue beige. The pictures are now better integrated with the text.

All the text on specific techniques has been rewritten and expanded, giving several examples and clear pictures. The list of techniques now includes hidden subsets, X-Wing, Swordfish & Jellyfish, and a very nice introduction to strong pairs and coloring. More will be added soon.

Ah yes, and I started BUG week.

Website Improvements

I have done a major overhaul of the main website. It has become rather messy with all the new additions. I now streamlined the design. Hope this attracts more visitors.

One of the improvements is a fully automated news archiver. I can upload any time anywhere a news item I deem worthy for the site, and indicate how long it will be on the front page. Anything that runs out-of-date is immediately placed in the news archive. The ‘read more…’ option is also a cool addition, saving space on the main page.

Clueless specials are now fully database driven. I can upload them straight from the CluelessMaker program.

Hanidoku will also be published in print, somewhere in September.

A privacy policy and copyright notice were added to the site.

The site is now validated for html 4.01, css and rss. Dunno if anyone cares, but it provides at least a minimum level of website code quality.

The sudoku solving guide has by far become the most popular page on the site. I’ve rewritten large portions, so it has a better consistency, smoother language and nicer pictures.

The easier level sudokus that I published on www.sudokuplaats.nl are now also published on the main site. This keeps beginners on the site a little longer.

HaniDoku

When you’re busy and have no time left, there is only one thing you can do: Start something new that even takes up more time!

When I was playing a game of Catan, I realized that the shape of the segments in this game could also be used for a new puzzle format.

A sudoku variant with hexagonal cells did exist, but it still had boxes and lines of equal length. So I decided to work out a concept with lines of different length, and drop the box constraint. This turned out to be a very good idea. With lines in 3 directions, the boxes would have so many intersections, that the puzzles would be too easy to solve.

The lines with different size open the way to new solving techniques. I found 3 already, and more are waiting to be discovered by me or others.

Tips and no tips

A post about tips.

I have been writing solving tips for killer sudokus on a new page in this blog. Eventually, these tips must be placed on my main website, but as long as I am writing them, I will post them here in the blog.

I have a donate button on my site for 3 months now. So far, I have received 1 donation, with more than 300 site visits each day, 9000 SudoCue downloads and more than 400 SumoCue downloads. I planned to drop the Google ads as soon as the tips were higher than the ad income. Alas!

Killing Time

My focus has been shifting back and forth, lately. My log shows that SudoCue has been downloaded more than 9000 times, but still there are not many responses. This made me put SudoCue on hold for a while.

I turned my attention to Killer Sudokus. Amazing how little software is available for Killers, while the Net is swarming with Sudoku programs. This time I decided to do it the right way. Be the first, be the best, be the benchmark.

The new program is SumoCue. It specializes in sudoku variants with irregular shapes, such as Killers and Jigsaws. It has a DLX solver that can solve any variant. It has a designer mode with the right tools to help you create jigsaws and killers. When puzzle makers use the program, they will attract players. The program has a custom file format, but also handles PS format for Killers.

The tools are limited, but very useful for both killer and jigsaw puzzles. After a few quick releases, the program has stabilized. It is well received, better than SudoCue. Maybe it was a good idea to use the same colors as Simple Sudoku to give the users a comfortable feeling. It worked for me. The light 3D effects create a smooth User Interface.

Support as usual through the forum. I use the program to create (Jigsaw) Killers. I post a few on my website, but I also have managed to sell a few to a publisher, along with a couple of Clueless Specials.

There is also a new release of SudoCue. I wrote a trimmed DLX solver to be used for random puzzle generation and optimization. My experience in DLX is now paying off. This new code is flamingly fast. I could even include multiple symmetry types for the generator.

Â