[Off Topic.] Sudoku.

By popular demand, my Sudoku tutorial. BE has implimented a rather...Cheap...Version of Sudoku on their site. (Funny, I just made an entry about it.) And, everyone in the SB is complaining. LOL. Great people...

Sudoku is an old game from Japan, a logic game. There is no math involved, just simple pattern recognition. Wikipedia defines Sudoku as:

Sudoku (: 数独, sūdoku), sometimes spelled Su Doku, is a placement puzzle, also known as Number Place in the United States. The aim of the puzzle is to enter a number from 1 through 9 in each cell of a grid, most frequently a 9×9 grid made up of 3×3 subgrids (called "regions"), starting with various numbers given in some cells (the "givens"). Each row, column and region must contain only one instance of each number. ...

A true Sudoku can be solved without guessing.

For demonstration purposes, I've taken a screen shot of an easy-level Sudoku from Web Sudoku

The gist: You get numbers, 1-9, and put them in the boxes. Only one number can occupy the box, no duplicates can appear in any 3x3, no duplicates in any row, no duplicates in any column.



See the 5's on the left hand side? They narrow down the options of the 5 appearing in the middle 3x3 on the left hand side.



Then, the 5 in the middle 3x3 narrows it down even more!



Where the 5 goes is marked with the red 5. Easy? Let's do another number. You'll see that I kept the 5 in that box. See the 2's on the left hand side? They narrow down the spaces for the 2 to appear in the middle left hand side 3x3. There's only one spot, so that's where we're going to stick the 2.



Now that we've gone through all the numbers using this method. (I've went through the puzzle and marked off all the numbers.) I tried not putting in all the numbers, even though I wanted to. LOL. We'll leave it at this.



You'll see the top middle 3x3 has only one box open. We can safely assume that would be a 1 in that box because it's the only number not in the 3x3, and, as the rules of Sudoku are, you can only have one of numbers in the 3x3s.



Now, see that column we put that 1 in? There's only one box without a number. We can, again, safely assume that a 6 goes in that box because, like the rules of Sudoku state, there can only be one instance of a number in a column.



If you're in question about what number should be in a box, use pencil marks. Pencil marks are little numbers, when I do Sudoku on paper, I write little numbers in the top of the box, that remind us of what the possibilities are. Sometimes, when you pencil mark all the boxes, you can see that some boxes may only have one pencil mark in them, and can safely assume that that's the number that goes in that box. The little red blobs over in the top right 3x3 are suppose to be 8's.



After switching inbetween the above mentioned methods, we eventually solve the Sudoku.



Of course, there's other methods that I haven't gotten into here. Maybe you can figure them out yourself. :)

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Posted by IdentityMIA to Off Topic. at 12/09/2005 10:28:00 PM