From: Matthew Moss <matt@...>
Date: 2008-11-08T00:01:55+09:00
Subject: [QUIZ] Sudoku Generator (#182)

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

The three rules of Ruby Quiz 2:

1.  Please do not post any solutions or spoiler discussion for this
quiz until 48 hours have passed from the time on this message.

2.  Support Ruby Quiz 2 by submitting ideas as often as you can!
Visit <http://splatbang.com/rubyquiz/>.

3.  Enjoy!

Suggestion:  A [QUIZ] in the subject of emails about the problem
helps everyone on Ruby Talk follow the discussion.  Please reply to
the original quiz message, if you can.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

## Sudoku Generator (#182)


_Quiz idea provided by Lloyd Linklater_

A bit over three years ago, we had a quiz to [solve sudoku puzzles] 
[1]. Now it's time to write a script that generates sudoku puzzles.

The output of your script should be the puzzle to solve. (Since we  
already have solver scripts from quiz #43, there is no need to output  
the solution.) In addition to generating the puzzle, you should adhere  
either one or the other of these two methods:

   1. Reduce a generated puzzle to the fewest clues that will still  
suffice for finding a solution. To your output, include an estimated  
difficulty level.

   2. Accept a command line parameter: the estimated difficulty level.  
Generate the puzzle such that it roughly matches that difficulty level.

The difficulty level should be a number from 1 (easiest) to 10  
(hardest). Difficulty level, obviously, is somewhat subjective.  
However, there are [various sudoku techniques][2] that may be able to  
help you decide whether a puzzle is more difficult or not. Some  
suggested metrics include: number of clues, number of "gimmes", number  
of possible solutions, cascading singletons, etc.


[1]: http://rubyquiz.com/quiz43.html
[2]: http://www.sadmansoftware.com/sudoku/techniques.htm