A computer science professor encourages his students to break Sudoku's rules

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#### Solution to Puzzle #2

I suspect that among the readers of this column, few are unfamiliar with Sudoku. The same cannot be said about Sudokill, a game invented for a graduate class I teach. Sukokill is a two-person game in which players try to force each other to violate the Sudoku rules.

Here's a quick refresher on Sudoku. The goal is to fill a nine-by-nine grid with digits between 1 and 9. Each digit should appear exactly once in each row, once in each column and once in each nonoverlapping three-by-three box starting from the upper left corner.

In the following example, we use 0 to represent a blank.

0 0 0 0 0 0 0 0 7 7 0 4 0 0 0 8 9 3 0 0 6 8 0 2 0 0 0 0 0 7 5 2 8 6 0 0 0 8 0 0 0 6 7 0 1 9 0 3 4 0 0 0 8 0 0 0 0 7 0 4 9 0 0 6 0 0 0 9 0 0 0 0 4 5 9 0 0 0 1 0 8

Consider the lower left box:

0 0 0             7 0 4             0 0 6             0 0 7             0 8 0             9 0 3             0 0 0 7 0 4 9 0 0 6 0 0 0 9 0 0 0 0 4 5 9 0 0 0 1 0

8

We know that of the five blanks in the lower left box, one must be 7. Because there is a 7 in the third column and also a 7 in the seventh (from the top) row, the only legal place for a 7 is to the right of the 6, yielding:

0 0 0             7 0 4             0 0 6             0 0 7             0 8 0             9 0 3             0 0 0 7 0 4 9 0 0 6 7 0 0 9 0 0 0 0 4 5 9 0 0 0 1 0

8

By contrast, the following would be illegal:

0 0 0             7 0 4             0 0 6             0 0 7             0 8 0             9 0 3             0 7 0 7 0 4 9 0 0 6 0 0 0 9 0 0 0 0 4 5 9 0 0 0 1 0

8

... because then there would be two 7s in the same row.

View
1. 1. alphachapmtl 12:04 PM 5/13/09

WShy so many pages? It's annoying!

2. 2. alphachapmtl 12:06 PM 5/13/09

unable to view article...

3. 3. milk 02:09 PM 5/13/09

4. 4. TTLG 11:44 PM 5/13/09

So the idea is to change a game of personal achievement into one of aggression against someone else? Wonderful. Like we don't have enough of those already.

5. 5. flakwack 02:48 PM 5/20/09

WHY would you use 0 and not leave the squares blank? Also, sudoku puzzles are typically square.

6. 6. Bigems 09:02 AM 5/22/09

why not use images instead of plain text! it's 2009 for petes sake

7. 7. acr 12:41 PM 5/22/09

Awkward for students and readers alike.

8. 8. Mirfy 12:53 PM 5/22/09

I liked the idea... a simple game with simple rules that creates a great challenge.

Congratulations !

9. 9. capissen 12:29 PM 5/23/09

Oh yeah, I use sudo kill every time one of my applications starts acting up!

10. 10. dmmiller2k 09:57 AM 7/2/09

Please post the text (non-HTML) version of this article, in one piece. The formatting detracts from the examples and makes them impossible to follow.

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