```Christer Nilsson wrote:
> Dirk Meijer wrote:
>
>>i wouldn't call it concise, it simply doesn't work.. probably an error
>>in porting to Ruby..
>
>
> It works. This is the complete code.
> Christer
>
> # Author: Kevin Greer (JavaScript),   Date: Dec 25, 2005  --  Copyright
> # Rewritten in Ruby by Christer Nilsson 2005-12-29
>
> class Sudoku
>
>   def initialize s
>     @s=s
>   end
>
>   def display
>     for a in 0..2
>       for b in 0..2
>         for c in 0..2
>           for d in 0..2
>             print " " + @s[a][b][c][d].to_s
>           end
> 			    print " |" if c<2
>         end
>         print "\n"
>       end
>       print "-------+-------+-------\n" if a<2
>     end
>   end
>
>   def solve a, b, c, d
>     return true if a==3
>     return solve(a+1, 0, c, d) if b==3
>     return solve(a, b+1, 0, d) if c==3
>     return solve(a, b, c+1, 0) if d==3
>     return solve(a, b, c, d+1) if @s[a][b][c][d]!=0
>
>     for digit in 1..9
>       if not occupied?(a, b, c, d, digit) then
>         @s[a][b][c][d] = digit
>         return true if solve(a, b, c, d+1)
>         @s[a][b][c][d] = 0
>       end
>     end
>     false
>   end
>
>   def occupied? a, b, c, d, digit
>     for x in 0..2
>       for y in 0..2
>         return true if @s[a][b][x][y]==digit # block
>         return true if @s[a][x][c][y]==digit # row
>         return true if @s[x][b][y][d]==digit # column
>       end
>     end
>     false
>   end
> end
>
> s =
>  [[[[0,0,0],[0,7,1],[0,0,5]],
>    [[5,0,0],[0,6,9],[0,7,1]],
>    [[0,7,1],[8,5,3],[4,2,0]]],
>   [[[0,1,0],[0,0,2],[0,0,0]],
>    [[7,8,0],[1,5,4],[0,9,2]],
>    [[0,4,0],[3,6,0],[1,8,0]]],
>   [[[0,6,4],[0,2,3],[0,5,0]],
>    [[9,0,5],[0,1,0],[0,0,0]],
>    [[7,0,0],[5,9,0],[0,0,0]]]]
> sudoku = Sudoku.new(s)
> sudoku.display
> print "\nsolving...\n\n"
> if sudoku.solve(0,0,0,0) then
>   sudoku.display
> end
>
>
>  0 0 0 | 0 7 1 | 0 0 5
>  5 0 0 | 0 6 9 | 0 7 1
>  0 7 1 | 8 5 3 | 4 2 0
> -------+-------+-------
>  0 1 0 | 0 0 2 | 0 0 0
>  7 8 0 | 1 5 4 | 0 9 2
>  0 4 0 | 3 6 0 | 1 8 0
> -------+-------+-------
>  0 6 4 | 0 2 3 | 0 5 0
>  9 0 5 | 0 1 0 | 0 0 0
>  7 0 0 | 5 9 0 | 0 0 0
>
> solving...
>
>  2 3 9 | 4 7 1 | 6 8 5
>  5 4 8 | 2 6 9 | 3 7 1
>  6 7 1 | 8 5 3 | 4 2 9
> -------+-------+-------
>  5 1 6 | 8 9 2 | 3 4 7
>  7 8 3 | 1 5 4 | 6 9 2
>  9 4 2 | 3 6 7 | 1 8 5
> -------+-------+-------
>  1 6 4 | 7 2 3 | 9 5 8
>  9 2 5 | 8 1 6 | 4 3 7
>  7 3 8 | 5 9 4 | 2 1 6
>
> Program exited with code 0

First Column has two 9's !

cheers

Simon

```