Monday Jan 01, 2007

Harder Sudoku and Solver

Over the holidays I cam across an even more difficult sudoku in the LA Times. Here it is:

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


And as I mentioned in my last sudoku blog, I have a solver and it is now available here. It is a pretty simple app but does provide for solving a puzzle or just doing an iteration to get a few solved cells. And if you press the solve button from the start it will tell you how difficult the puzzle is. The one above is 32.2.

Have fun!

Sunday Dec 17, 2006

Difficult Sudoku

I blogged about Foxtrot and Sudoku a while ago and it garnered a lot of interest. Given that, I thought folks may be interested in some difficult traditional sudoku puzzles I have come across.

The way I actually determine difficulty is from a program I wrote that solves the puzzles. The program implements a number of techniques to solve the puzzles and determines how hard it is based on the techniques that must be used and how quickly it can be solved. I hope to have the solver hosted where you can get to it soon, so stay tuned.

In any case, here is the hardest puzzle I have come across.

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


And another difficult one.


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

Give them a try!
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