Category: Sudoku Variants

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Sudoku To Kakuro

Sudoku To Kakuro

I’ve been doing Cross-Sum puzzles for many years, but now that it’s called Kakuro (abbreviation of Japanese kasan kurosu: addition cross), it seems somehow new. Certainly the Puzzle book publishers think so. Where there was previously only a section in a crossword puzzle book there is now entire puzzle books devoted to Kakuro.

In solving these kinds of puzzles it may be useful as a solving aid to know about minimum and maximum values for the length of each clue number and a way of dealing with missing and required values in partial sums. One such way is to map missing values to 0 and required values to 1, to get a bit-wise string of bits for which bit-wise logical operations can be performed: and, or, exclusive or, not.

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Sudoku + Paint By Numbers

Sudoku + Paint By Numbers

For me, before I discovered Sudoku there was Paint By Numbers (Nonograms). I was particularly fascinated by painting (shading actually) logically. There are three books of Paint By Numbers Puzzles that I’m aware of: one is authored by Games Magazine, called Paint By Numbers and the other two are by Kathy Weaver, called Art Puzzles By Number and More Art Puzzles By Number.

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Battleship Sudoku

Battleship Sudoku

Two games in one: Battleship and Sudoku. There are fewer Sudoku clues and added Battleship clues. Use both sources to solve both objectives. The battleships in the fleet are either horizontal or vertical and are totally non-adjacent to each other. The border numbers show the number of cells in a row or column that are contained on one or more battleships.

This variant stems from the 2007 Sudoku Championship Puzzle Instruction Book (in pdf format)

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Shogi Sudoku

Shogi Sudoku

I have been a long time Shogi (Japanese Chess) player. The problem is too few worthy opponents. This may be due to the fact that playing Shogi for any length of time fosters frequent sacrifices, which totally ruins you for regular chess.

Shogi is played on a 9 x 9 square board and your pieces are pointing away from you. Your opponent’s pieces are pointing toward you. One major feature that distinguishes Shogi from Western Chess is that pieces that you capture become yours to play again anywhere unoccupied on the board. (pawns only drop onto your non-pawn lanes.) As a result, there are no draws in Shogi.

It took me about a month to recognize the Japanese characters reliably, without referring to the names and pictures. Once you study the characters, they are quite dissimilar from each other and have unique identification areas. While western chess emulates middle-ages warfare, Shogi is more a metaphor for aerial warfare a la World War 1 (and perhaps 2).

Other resources for this game include shogi.net, shogi.com, the Ricoh Shogi Club and the Computer Shogi Association which tracks the World Computer Shogi Championships.

For the last few weeks, I’ve been swamped with extra curricular activities which has constrained my writing here. I hope to resume in May.

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More 2007 World Sudoku Championship And More Color Sudoku

I’m slowing catching up on the news: On February 3, 2007, The World Puzzle Championship announced the U.S. Sudoku Team Members for the 2007 World Sudoku Championship.
They are:

  • Nick Baxter, Captain and Members:
  • Grayson Holmes (placed 50th in 1st World Sudoku Championship March 2006),
  • Wei-Hwa Huang (placed 2nd),
  • Jonathan Rivet,
  • Jim Schneider (placed 28th),
  • Thomas Snyder (placed 1st),
  • Jason Zuffranieri

In the livejournal community called worldpuzzle, there are many details about the upcoming World Championship including instructions (a downloadable pdf file).

There are new kinds of puzzles depicted, which are different from those in 2006. I especially like the puzzle called Paint It Black, which is a blend of a Sudoku Puzzle and a Paint By Numbers Puzzle.

Two Color Sudoku Sites that I noticed are a Color Sudoku Journal Article and a Color Sudoku Solver in MS Excel.

The Journal of Chemical Education is publishing an article called “Chemistry of Art and Color Sudoku Puzzles” by Michael J. Welsh of the Department of Science and Mathematics, Columbia College Chicago, Chicago, IL 60605

The abstract describes what may be a fascinating connection between chemistry and color. Unfortunately a paid subscription to the Journal ($45 for US Individual) is required for both the full text of the article and the 3 puzzles and solutions file shown in the article.

Quite free is the Color Sudoku Solver via Excel Spreadsheet by Erkki Hartikainen: downloadable xls file. This spreadsheet solver permits you to map the digits and colors in either direction.

One particularly handy feature is the ability to modify colors depending on your own eyes’ ability to distinguish contrasting colors. The color solver is based on a number Sudoku solver by David Ireland.