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

Warm-up Puzzle:
Suppose it is the row player's move in the following situation (where letters represent blanks) and the row player can move anywhere:

5 7 6 1 4 9 2 3 8 8 4 9 3 7 2 5 1 6 3 2 1 8 6 5 9 7 4 4 6 3 7 9 1 8 5 2 1 5 8 6 2 4 7 9 3 7 9 2 5 3 8 4 6 1 2 1 4 9 5 6 3 8 7 9 8 7 4 1 3 6 A 5 6 3 5 B 8 7 1 C 9

How can the row player force a win (that is, force the column player to make an illegal move)?

Solution to Warm-up Puzzle

Now it's your turn, but this time we'll favor the column player.

1. Can the column player force a win in two moves given the following board? (Here the column player can begin by moving anywhere.)

8 1 5 3 4 9 2 6 7 7 A 4 B 5 1 8 9 3 3 9 6 8 7 2 4 1 5 1 4 7 5 2 8 6 3 9 C 8 2 9 3 6 D E 1 9 6 3 F 1 7 G H I 2 3 1 J 8 K 9 5 6 6 7 8 1 9 5 2 3 4 L 5 9 2 M 3 1 7 N

2. Here's a harder one. Can the column player force a win in three moves given the following? (Again the column player can begin by moving anywhere.)

7 A 5 8 1 3 2 9 B C D 1 4 7 6 5 E F 3 4 G 2 5 9 H 1 7 9 1 4 5 ? 7 3 2 6 I 5 7 3 6 2 J 4 9 6 2 3 9 4 1 7 K L 1 3 2 6 9 8 4 7 M N 8 O P 2 5 9 3 1 Q 7 9 1 3 R 8 6 2

Solution to Puzzle #2

Here's an invitation. If you can produce a four-move forced win on a board initially having more blanks than assignments, please send it to me at shasha@cims.nyu.edu. Also, please play Sudokill at Yu Yiwen's Web site designed by a graduate student at New York University: http://homepages.nyu.edu/~yy497/projects/showcase/SudokillWebGame

Dennis Shasha is at the Courant Institute of Mathematical Sciences, New York University. His most recent puzzle book, Puzzles for Programmers and Pros, was published in May 2007 by John Wiley and Sons/Wrox.

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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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