From: Karl von Laudermann <karlvonl@...>
Date: 2005-08-20T23:41:17+09:00
Subject: Re: [QUIZ] Sodoku Solver (#43)

In article <15hhca6w53u5l.dlg@example.net>,
 Chris Game <chrisgame@example.net> wrote:

> Karl von Laudermann wrote:
> 
> > Heh. I already wrote a Sudoku solver back in May; all I have to do
> > is change the input/output format a bit to match the quiz
> > example. In the meantime, here's a harder puzzle to test your
> > programs with:
> 
> Why is it harder? If an algorithm works, all solvable puzzles are
> the same?

Well, it's harder for a human to solve; I forget where I snagged it 
from, but it was labelled as "really hard". And it took my solver 
program a whole 7 seconds to solve it (on my old computer), while other 
examples I tested it with took less than a second to solve. So it's 
probably useful for profiling your program's performance.

Ok, here's one that's *not* solvable, useful for making sure that your 
program can handle such a case gracefully:

+-------+-------+-------+
| _ _ 1 | _ 2 _ | 8 _ _ |
| _ 7 _ | 3 1 _ | _ 9 _ |
| 3 _ _ | _ 4 5 | _ _ 7 |
+-------+-------+-------+
| _ 9 _ | 7 _ _ | 5 _ _ |
| _ 4 2 | _ 5 _ | 1 3 _ |
| _ _ 3 | _ _ 9 | _ 4 _ |
+-------+-------+-------+
| 2 _ _ | 5 7 _ | _ _ 4 |
| _ 3 _ | _ 9 1 | _ 6 _ |
| _ _ 4 | _ _ _ | 3 _ _ |
+-------+-------+-------+

-- 
Karl von Laudermann - karlvonl(a)rcn.com - http://www.geocities.com/~karlvonl 
#!/usr/bin/env ruby
require "complex";w=39;m=2.0;w.times{|y|w.times{|x|c=Complex.new((m*x/w)-1.5,
(2.0*y/w)-1.0);z=c;e=false;49.times{z=z*z+c;if z.abs>m then e=true;break;end}
print(e ?"  ":"@@");puts if x==w-1;}}