Robert Katz

Posted on March 23, 2008March 27, 2008 by Robert Katz — 2 Comments

Fillomino On Sudoku

Nikoli invented this puzzle in 2001. Once called Allied Occupation, Fillomino is a merger of the words Filled and Polyomino. A Polyomino describes the shapes assumed of a varying number of multiple cells, that have at least one side touching another cell.

Wikipedia describes this as a logic puzzle and gives more elaborate rules, particularly about the possibility that 2 or more given numbers could belong to the same pentomino. Solution methods are also offered.

As this is a fairly popular puzzle in its own right, there are a variety of Websites that offer Fillomino:

Puzzle Club a British Site offers Many Math, Number, Logic, and Word Puzzles in addition to Fillomino. Registration is 10 Pounds/Year
Vegard Hanssen’s Fillomino Puzzles, which has more than 16,000 Puzzles in its database. Mr. Hanssen is a perl programming language afficionado, See his perl scripts for generating his name(s).
Brainbashers.com provides 8x8s, 12×12 and 16×16 size grids for their daily Fillomino puzzles.
Simon Tatham has a similarly named puzzle called Filling on his website.
Finally, Djape.net has an interesting discussion about Fillomino Skyscrapers which is a mashup of Fillomino and what I called buildings. The numbers on the outside are clues to how many “buildings” can be viewed from that location. Higher valued numbers block lower valued numbers, but offer interesting clues about the composition of the row or column. See my Sudoku Buildings Cartoon posted last July 15, 2007.

Get your fill of Fillomino! (but take your time.)

Posted on March 16, 2008March 27, 2008 by Robert Katz

Signal Pennant Sudoku

The use of flags and pennants as communications has intrigued me. According to the Sea Flags web site, Athenian (Greek) ships were first known to signal each other with brightly colored flags. Time passed and Navies of various European countries began to devise more sophisticated communication using semaphores and flaghoists after 1750.

The current situation is depicted in the International Code of Signals and in particular, pennants representing the digits one through nine are shown in the cartoon.

It’s an easy leap to create a sudoku puzzle using these pennants as stand-ins for the normal digits. You may do this puzzle calmly and in a room that has been becalmed as well.

Posted on March 9, 2008 by Robert Katz

Time Change Sudoku

In most of the United States (But not Arizona nor Hawaii), Daylight Saving Time began early this morning, March 9. I find out how many clocks I’m governed by when I do this twice-yearly ritual. Occasionally, the clocks I missed last fall are telling accurate time now and they stay unperturbed.

I found an interesting Web Site called webexhibits.org describing Daylight Saving Time and which uses a kind of a mind-map (that they call clouds or nodes) to display information, in lieu of powerpoint-like slides. For this, you must let go of outlines and hierarchy.

Wikipedia has a colored map of use and abstinence of DST (or Summer Time) Worldwide.

To honor the induced chaos of time changes, I’ve created a Sudoku Puzzle which uses analog clock faces. Take your time.

Usually at this time of year, the Yearly Sudoku World Championship announces itself. Based on a cursory web search, The 2008 Sudoku World Championship will be held on April 14-17, 2008 in Goa, India on the West Coast in the Konkan region and bordering the Arabian Sea.

Registration apparently started March 8, 2008. This year publicity is currently sparse, so much information emanates from a Technical Blog called Jalaj.net. Revisit it during the next month, for further details.

Posted on March 3, 2008March 26, 2008 by Robert Katz

Scrabulous On Sudoku

Based on the March 2, 2008 New York Times Article about the dilemmas posed by Scrabulous™, an online game invented by Rajat and Jayant Agarwalla, from Kolkata, India, this cartoon was born.

The online game appears to be an intimate embrace of Scrabble™, currently physically sold and distributed by Hasbro, Inc. and Mattel Inc., who together divide up the World Rights to sell the game.

As is becoming clearer in the 21st century, having an online version stimulates sales of physical (original) versions. By squelching the online versions, these companies risk severe sales reductions due to bad publicity and a collective vow to boycott those company products. By not squelching the online versions, the companies must adapt (like the music and movie industries are [not] doing) or go out of business anyway. Choose wisely.

I thought it would be amusing to mashup Sudoku with Scrabulous. You can play it with either game goal in mind, but pursuing both will no doubt mentally bifurcate you, which is a serious condition, sometimes leading to split personalities.

Posted on February 25, 2008 by Robert Katz

Eye Chart Sudoku

Have you ever been to the Eye Doctor (Optician, Opthalmic Dispenser) and got tested for your visual acuity and thought: “This test is too easy!” ? I have. The result is this cartoon. I heartily recommend it to all who have to get their vision checked. Try to talk your doctor into using this chart rather than his. You may both be surprised at the results. Consider it a Vision Quest.

Posted on February 17, 2008 by Robert Katz

Spider Sudoku

While escorting a spider out to the back yard, I mused about how spiders might solve Sudoku puzzles. This is the result. It relates to the party game of Twister patented by Charles F. Foley and Neil W. Rabens in 1966 and originally sold in the United States by Milton Bradley Company.

According to Torsten Sillke, The original inventor, Reyn Guyer, designed a Polka Dot Mat For store display purposes, but later converted it into a game and called it “Pretzel”. Currently, Hasbro Toys which took over Milton Bradley in 1984 sells the game.

I imagine that Spiders “instinctively” solve the puzzle, given the various starting numbers by transitioning from all instances of one value ( such as an 8 ) to all instances of the next value chosen. This is rather unlike humans, who use logic and solve by rows, columns and blocks.

The underlying (!) puzzle is considered hard, but may be made easier by taking the spider’s hints.

Posted on February 4, 2008 by Robert Katz

Ripple Effect Sudoku

This Puzzle uses various sized grids to fit sets of pentominos within. I’ve chosen a 9×9 grid. I think the name, Ripple Effect is suggestive of bigger integers making a bigger splash given their unneighborliness in the rule set. There are no tip sheets as yet, although a strategy may be like that of Paint By Numbers, where you have to account for not only where candidate numbers could be, but also where they cannot be. Ripple Effect was created by Nikoli in 1998.

There are some sites with Ripple Effect Puzzles:

You Play.com, an online puzzle site with free and paid memberships. Getting a free membership is a chore, if not impossible. The form decided my email address was already in use and rejected its association with a new userid! Clicking on Account details made no impression on the script.

Online Puzzle Ripple Effect has multiple puzzles of sizes 8 x 8, 10 x 10, 18 x 10 and 24 x 14.

Ewe Weidemann’s Sudoku Variants Page.
This site has a huge number of Sudoku and other Puzzle variants well organized, although mostly one example of each kind.

I may have to acquire some Nikoli published puzzle books on this variant.

Posted on January 28, 2008 by Robert Katz

Sudoku Songs

I vacationed in Canada (Vancouver B.C.) this weekend. In lieu of the series of Sudoku variant cartoons and commentary this week, I decided to search the youtube.com archives for Sudoku Songs of various kinds. Here are the results with some commentary.

Let’s Sudoku!: Sudoku Song. This is performed as Alternative Music. I was amused that the puzzle is filled in each row from left to right. Very satiric.

Sudoku Song. This is rendered as a Folk Song. Click on the lower right hand corner x to undisplay the ads.

Sudoku Rap. This is edited to eliminate the most common Rap vocabulary, but not seamlessly.

I’m starting to dream in Sudoku by Mitch Benn. This is easy listening music and cute! The puzzle appears to be solved realistically.

Time Lapse Video. A 17 second Jazz version of a “now you see it, now you don’t” (mostly you don’t very well) Sudoku puzzle being solved. The video is a cliff-hanger.

Suicide by Sudoku. Perhaps the Beer had a role to play. After all, it was only of medium difficulty. This is uses guitar solo music.

Sudoku on Rubik’s Cube while you watch. Children annoying the young solver in his room. Non-descript music.

Newspaper Sudoku. A self-solving do-it-yourself kit version stimulated by Zorba the Greek Music.

Two Wonderful Sudoku Board Abstract Patterns are shown:
Green Medium #1 and Gray Easy #2. (Electronic Music).

Finally, to indicate that the human filter is still severely needed in search engine technology, here is In Contra Sudoku Live. A hard rock rendition having nothing to do with the puzzle except the name. The last intelligible word is the introduction to the piece. The performance is intrumental electric guitars and Drums with intermittent screeching.

Posted on January 21, 2008January 21, 2008 by Robert Katz

Mayan Sudoku

In only a few more years, by December, 21, 2012, that year’s Winter Solstice, the Mayan Calendar (Long Count) will be completed. See “The How And Why Of The Mayan End Date In 2012 A.D.” by John Major Jenkins. It has been keeping track for the last 5125.36 years, since August 11, 3114 B.C. From the accuracy of the Calendar, myths of the end of the world with the end of the calendar have emerged. So the next 5 years will be quite interesting.

The site Mayan Numbers is the reference for Mayan numbers and their names.

There is a Mayan to Arabic Number converter located in The Mayan Astronomy Page.

Some information about the history of Mayan numbers is given in Mayan Mathematics page

A general introduction to Mayan numerals is located in Mayan Numerals.

It is fascinating to “try on” the various (obscure) number systems and other representations of the digits 1-9 while playing a Sudoku that is not difficult but not easy either.

Posted on January 14, 2008 by Robert Katz — 1 Comment

Repeat-Letter(s) Sudoku

A (Mensa!) Puzzle Book by Walter Mackay called Repeat-Letter Sudoku caught my eye this week.

This book offers puzzles where there is one (or more) doubled letter(s). In the Cartoon, there are two repeated letters: U and A. No matter. Just do the Sudoku Puzzle as usual and treat each of the pair as two different numbers.

It may help to write the same letters in unique ways: one in block letters and one in cursive or lower case. Alternatively, you can just keep count in every row, column, and block that duplicated letters show up exactly twice.

I like the effect of the no duplicates rule in the original sudoku being relaxed. It forces me to look anew at the puzzle and how it can be done, without prior built up procedural blinders. Interestingly enough, this particular variant appears studiously ignored by the rest of the internet.

I suppose if this carried far enough, it becomes simple to solve (e.g. All but one letter is duplicated 8 times). Don’t do too many of these; you may have to complain to your Eye Doctor that you’re seeing double!