Sudoku is a logic-based number puzzle that does not involve arithmetic. Although first published in an American puzzle magazine in 1979, Sudoku gained popularity in Japan in 1986 before becoming an international craze in 2005. The goal is to enter a numerical digit from 1 through 9 in each cell of a 9x9 grid, without repeating a number in any row, column, or 3x3 sub-grid. After picking up some on tips at the following sites, you can try your skills at the Surfnetkids Daily Sudoku Puzzle.
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British journalist Paul Stephens explains the Sudoku-solving techniques of crosshatching (eliminating rows and columns), slicing and dicing (a different way to look at crosshatching), and penciling in. When you've solved as much of the puzzle as you can using these three techniques, Paul recommends that you "start finding numbers for squares instead of squares for numbers" by applying five rules. He summarizes it all by offering three keys to successful Sudoku solving: total accuracy, completeness, and maintenance.
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Japanese puzzle magazine Nikoli divides their Sudoku lessons into twelve classes. Starting at Beginner's Class 1, Puzzle Japan provides lots of examples of crosshatching (without labeling it as such.) Their English is rough in a few spots, but the quality and quantity of the animated illustrations make this a great site for visual learners and K-6 students. "Little by little complicated, but don't worry."
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This eleven-page free PDF ebook from Michael Mepham of the Daily Telegraph requires the free Adobe Reader. For solving really difficult puzzles, it introduces methodological analysis and bifurcation, "the technical terms for picking a likely pair of numbers, choosing one and seeing where the number you have chosen gets you." It is an excellent resource for high-school students and adults, but does make reference to "a couple of slugs of scotch at the pub," so it may not be appropriate for every audience.
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To be used as a last resort when solving paper-and-pencil puzzles, or as a learning tool, Sudoku Helper will step you through a solution to a puzzle of your choosing. Start by entering your puzzle in the little grid, using the Save button as you go along. Click Take Step to run the solver through each of four tests. Harder puzzles will not get solved completely, but with this extra help you may be able to continue the game yourself. A unique feature of the solver is the ability to email the game to a friend.
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This four-page tutorial from Pappocom makes extensive use of mouseovers. Place your mouse over any of the illustrations (no clicking necessary) to see the solution explained in the corresponding paragraph. The best reason to visit are the numerous examples that will help reinforce basic Sudoku strategy. "There's no right or wrong place to start but we do have to start somewhere, so let's look at the three boxes at the top of the puzzle."
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By Barbara J. Feldman. Originally written on Mar 29, 2006. Last Modified on Jan 09, 2008.
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Buy Sudoku Tips Printable for $2.00 or try a FREE trial of the Printables Club
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Honorable Mentions
The following links are either new discoveries or sites that didn't make it into my newspaper column because of space constraints. Enjoy!
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