It’s still a few months away, but publicity has already started for the Sudoku National Championship in Philly on October 24-25.  The championship will include guest appearances by Will Shortz and Maki Kaji, credited as “the man who gave sudoku its name.”  (The creator of sudoku is actually American Howard Garns.)

It looks like they learned a lot in the first go around and have made a number of improvements for this years competition.  Most notable are help determining which level you belong in and a prize structure that awards more to the third place winner in the advanced level than the first place winner in the intermediate level.

A while back there was a post on Passion for Puzzles about a new kind of puzzle called KenKen puzzles.  The puzzle was featured on the Times Online site where a few puzzles were printed along with an article about the puzzles’ creator Tetsuya Miyamoto.  To be honest, I only skimmed the article.  It seemed to be more about the creator’s teaching philosophy than about puzzles.

KenKen puzzles are a variation of killer sudokus.  The layout is exactly the same.  The only difference is that the groups of boxes have not only a number, which in killer sudoku would represent the sum of the numbers in the boxes, but they also contain an arithmetic operator which tells you what to do with the numbers.  They need not only be sums.  They can be differences, products, or quotients.

Enjoy!

After coming off of my brief hiatus, I discover that the World Sudoku Championships have already come and gone.  Congratulations Thomas Snyder and the Czech Republic for their victories in the individual and team competitions respectively.

The site Sudoku World has an amusing little feature called “Safe For Work” sudoku.  The idea is similar to that of the boss key which was a feature of some old games.  The idea was that you could hit a button when your boss came by and look like you were doing something productive when you were really playing a game.  The same is true of the Safe For Work Sudoku.  It’s disguised to look like a spreadsheet that you’re working on.  Now, your boss will never know how many hours you spend playing Sudoku at work.

There was an article in Science Daily today about something called “color sudoku.”  Color sudoku is part of a research project at the University of Warwick regarding “Empriical Modeling.”  It’s not entirely clear to me what this is from the article, but the general idea is to look at the interactions between logic and perception.  This is where the color sudoku comes in.  In color sudoku, each digit is assigned a color and each square that has that digit in it is filled with that color.  The empty squares are filled with a combination of all of the colors for all of the possible digits that could go in that square.  This is intended to give you clues as to what should be there.  Darker colors, for example, will indicate more possibilities and, if the color in an empty square exactly matches that of a digit, you know which digit must go there.

While playing around with it, it was hard for me to see, at first, the advantage of the colors, but as more digits are filled in some patterns did begin to emerge.  Though I’m not sure if logic and perception ever actually met.  It’s an interesting idea and sudoku is a very accessible example, though likely not the best.

Wei-Hwa Huang who wrote the puzzles for the first US Sudoku Championship has posted two puzzles on his blog that were not included in the competition.  The two puzzles were rejected, it seems, because they were a little bit too tricky.  Try them out and see what you think.

It’s funny how these things work…  This weekend, the World Sudoku Champion became the US Sudoku Champion.

I mentioned back in May that the first US Sudoku National Championship would be happening this October. Well, it’s happening this weekend. The event page mentions Will Shortz and Merl Reagle prominently (there is even a Q&A with Reagle), so I’m guessing that the event is trying to gain some publicity from the cruciverbalist corner. The site also mentions Wei-Hwa Huang and Thomas Snyder who are, no doubt, the odds-on favorites to win the competition.

I’m currently lamenting the fact that I no longer live in Philly, or I would be there for it this weekend. Still, I’m curious to see what happens and if there will be any dark horse contenders.

I recently came across a site that featured Top Hat Puzzles.  Top Hat puzzles are a sudoku variation that involves a differently shaped grid.  The grid is smaller and twisted 45 degrees.  There are 22 squares in the grid and there are 12 internal areas of six squares each.  The object, as with all sudoku puzzles, is to fill each internal area using each of the digits 1-6 exactly once.  What is interesting about this puzzle is the layout of the internal areas.  In a standard sudoku, each square is part of three internal areas: a row, a column, and an internal square.  In this puzzle, some of the squares are a part of four internal areas, others are a part of two.  I won’t post a puzzle here for copyright reasons, but if you’re curious about how this layout works, you can click over.

The puzzles are small, and can be solved quickly.  It’s also interesting to note that the site’s author also seems to be working on two other sudoku variations.  One is called sequential sudoku and the other five star sudoku.  Links to drafts of these puzzles can be found at the bottom of the page.

Here’s a puzzle that I’ve had kicking around for a while. It’s a sudoku variation that I’m calling Circle Sum Sudoku. It’s basically a cross between kakuro and sudoku. The idea was to have a sudoku grid where the clues are unknown to start. This gave me the idea of having a kakuro like puzzle to determine the clues. The result is this puzzle.

You’ll notice that there are circles in the grid, and numbers along the top and left sides. The numbers above the columns indicate the sum of the digits in the circles in that column. The numbers beside the rows indicate the sum of the digits in the circles in that row. The numbers in the grid to the right indicate the sum of the digits in the circles for the internal squares.

I’ve got some ideas for some additional puzzles, where you not only have to find out what the internal clues are, but also where they are. More on that later. For now, enjoy!

pdf solution

The Philadelphia Inquirer will be sponsoring a National Sudoku Championship hosted by Will Shortz.  The event will take place in Philadelphia, Pennsylvania on October 19-21.  This is the first National Sudoku Championship in the US and prizes will range from $100 to $10,000, which goes to the winner along with a trip to the World Championships next year in India.

Sudoku Tiger is a site that offers software for playing Sudoku, Killer Sudoku, and Hashiwokakero (here shortened to Hashi.)  The software is not free, but there are free puzzles of all of the featured kinds available on the site.

Of particular note is the solving guides for sudoku, killer sudoku, and hashiwokakero.  Sudoku solving guides are a little dime a dozen these days, but the it’s worth checking out the guide for hashiwokakero.

I recently came across a site featuring Sudoku-Ball. The Sudoku-Ball takes overlapping sudoku puzzles to a new level. The idea is that the overlapping puzzles are layed out on the surface of a sphere so that they eventually the chain will wrap back around to the same puzzle again.

The site makes the game available as a Java applet, but it’s not easy to use. There are multiple steps before you can actually play the game. Still, it’s worth a look.

I’ve decided to start posting some sudoku variations that I’ve been playing around with.  I wanted to start with a variation that I hadn’t tried before, but since this is opening week for baseball, I decided to go with a new Scoreboard Sudoku instead.

I really like this variation.  There is definitely some interesting logic required for solving it.  Unfortunately, you have to know baseball to solve it.  Now, baseball is huge in Japan, so maybe there is a demand for this kind of puzzle.  Still, I’m working on ways to incorporate the nice aspects of Scoreboard Sudoku into a variation that doesn’t require sports knowledge.

This puzzle is similar to the last one.  There is a lot of variation potential here that I want to explore, mostly with different scoring options.  That, however, will be for another day.  Rules for this puzzle can be found at the link above or in the pdf file below.  Enjoy!

solution pdf

After finishing second in the first World Sudoku Championship last year, Thomas Snyder took home the top prize this year.  Last year’s winner, Jana Tylova, did not finish in the top three.  The final puzzle can be found here.  It’s a “Jigsaw Sudoku” that’s very different from the the puzzles that usually bear that name.

This year’s team title went to Japan.