# Sudoku Difficulty

**URL:** <https://www.ruby-forum.com/t/sudoku-difficulty/175773>\
**Category:** Ruby\
**Created:** [September 19, 2009, 10:28am UTC](https://www.ruby-forum.com/t/sudoku-difficulty/175773 "2009-09-19T10:28:08Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![vipulkelkar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/57b2e6/32.png) [@vipulkelkar](https://www.ruby-forum.com/u/vipulkelkar)\
**Post date:** [September 19, 2009, 10:28am UTC](https://www.ruby-forum.com/t/sudoku-difficulty/175773/1 "2009-09-19T10:28:08Z")

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Hi guys

I am trying to develop a sudoku app in ruby.  
I want to have the difficulty levels…say easy Medium and hard

What decides the level of difficulty.How should i place my numbers  
depending upon the difficulty level selected

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**Author:** ![vipulkelkar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/57b2e6/32.png) [@vipulkelkar](https://www.ruby-forum.com/u/vipulkelkar)\
**Post date:** [September 19, 2009, 12:51pm UTC](https://www.ruby-forum.com/t/sudoku-difficulty/175773/2 "2009-09-19T12:51:02Z")

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On Sat, 19 Sep 2009 03:28:10 -0500, Vipul K. wrote:

> Hi guys
> 
> I am trying to develop a sudoku app in ruby. I want to have the  
> difficulty levels…say easy Medium and hard
> 
> What decides the level of difficulty.How should i place my numbers  
> depending upon the difficulty level selected

Not a Sudoku expert but is it just the number of numbers initially  
displayed? ie the less to start with the harder the game?

cheers,

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<div class="post-metadata">

**Author:** ![vipulkelkar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/57b2e6/32.png) [@vipulkelkar](https://www.ruby-forum.com/u/vipulkelkar)\
**Post date:** [September 19, 2009, 1:30pm UTC](https://www.ruby-forum.com/t/sudoku-difficulty/175773/3 "2009-09-19T13:30:15Z")

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Mark:

> On Sat, 19 Sep 2009 03:28:10 -0500, Vipul K. wrote:

> > I am trying to develop a sudoku app in ruby. I want to  
> > have the difficulty levels…say easy Medium and hard

> > What decides the level of difficulty.How should i place  
> > my numbers depending upon the difficulty level selected

> Not a Sudoku expert but is it just the number of numbers initially  
> displayed? ie the less to start with the harder the game?

I don’t think it’s this simple – a proper Sudoku should be always  
solveable without taking a guess, and I think the hardest are  
the ones that put the solver in a position where there’s only  
one non-guessing move on the whole board (or, at least, as few  
such moves as possible), and taking this move leads to another  
such hard situation.

— Shot

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<div class="post-metadata">

**Author:** ![vipulkelkar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/57b2e6/32.png) [@vipulkelkar](https://www.ruby-forum.com/u/vipulkelkar)\
**Post date:** [September 19, 2009, 3:53pm UTC](https://www.ruby-forum.com/t/sudoku-difficulty/175773/4 "2009-09-19T15:53:05Z")

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-------- Original-Nachricht --------

> Datum: Sat, 19 Sep 2009 17:28:10 +0900  
> Von: Vipul K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> An: removed\_email\_address@domain.invalid  
> Betreff: Sudoku Difficulty

> Hi guys
> 
> I am trying to develop a sudoku app in ruby.  
> I want to have the difficulty levels…say easy Medium and hard
> 
> ## What decides the level of difficulty.How should i place my numbers depending upon the difficulty level selected
> 
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).

Dear Vipul,

> What decides the level of difficulty.How should i place my numbers  
> depending upon the difficulty level selected

I am not quite sure whether the computational effort of a particular  
implementation in solving a problem can really be mapped to the  
psychological difficulty a subject finds in solving it.  
This caveat apart, I’d take your application, or this one, if you are  
not yet ready:

[http://gecoder.rubyforge.org/examples/sudoku.html](http://gecoder.rubyforge.org/examples/sudoku.html)

and generate and solve some problems to see how big the range of  
computation times is.  
Maybe you also have some Sudokus some expert has classified, to see  
how long a difficult one takes in contrast to a simple one, given your  
implementation ?

Best regards,

Axel