This is an object-oriented Sudoku Solver combining the "cross hatching" strategy with a backtrack algorithm. It solves easy puzzles in about 600 µsecs and really hard ones usually in under 150 msecs (when compiled) on my old AMD Athlon XP1800+. The most evil one I could find is in the screen shot.
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'Windows API/Global Declarations for :Ulli's Sudoku Solver (4x faster again)
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a few
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Exchange the 1st and 2nd "If"-line in AllAgree; this speeds up certain puzzles by more than 10% - the reason being that the puzzle is solved row-wise and therefore a row will statistically more often "disagree" than a column. (If this comment was disrespectful, please report it.)
Its a great solution and surely it was good fun (and hard work) for the author. But what is the fun for the user of this app? ;-) Forgive me, Ulli, here are my five ***** and regards - LiTe (If this comment was disrespectful, please report it.)
Enhancement suggestions: Add the ability to load (and save) puzzles. Also, add a (Hints off/Hints on) button (see below).
LiTe,
By clicking on Hide and then Solve, you can use the "Solution" side of the form to work on the puzzle. You would would have to comment out the tool-tips in the source code or have a (Hints off/Hints on) toggle similar to Hide. (If this comment was disrespectful, please report it.)
Wow Ulli!... Derio's hint, improved in version 2, is really the right strategy: the one used by human sudoku solvers... I verified the Beast450 sudoku passing from 98,719,671 steps to 9,948 (and from 40 minutes to 3 seconds on my machine). About 10,000 times faster...:)
Good version 2, Ulli!
Waiting for more improvements on the interface...
(If this comment was disrespectful, please report it.)
...sorry Derio that I referred to your idea as "his idea" in the text above, should of course be "her idea". As an excuse may I say that in long-nose-contry first names ending with "o" are usually male. *grin* (If this comment was disrespectful, please report it.)
Ulli, I received your mail, but I'm not able to answer at that yahoo email address (Mail Delivery System says:SMTP protocol diagnostic: 554 delivery error: dd This user doesn't have a yahoo.com account), can you send me an alternate email, please?...:)
(If this comment was disrespectful, please report it.)
This software is too slow trying to work out puzzles. You need to go back and rethink how to make this faster, plus the colours arent the best either. Unless you're still living in the 70's. (If this comment was disrespectful, please report it.)
it is very fast here, only a few u seconds, you say it is too slow, maybe you used the animation, which is designed to be "slow" enough for human eyes to see, otherwise, you maybe using 8086.
(If this comment was disrespectful, please report it.)
Sure, Jason... What would be the best colors? - I'll do my utmost to meet your personal taste. Anything else you want me to do? Change my name perhaps? Commit suicide? (If this comment was disrespectful, please report it.)
If you think this software is too slow, I would challenge you to write a faster version. It's easy to criticize, but harder to support your criticism. (If this comment was disrespectful, please report it.)
Would it be possible to determine if a unique solution exists? I am a purist at heart and try and solve puzzles without guessing. (If this comment was disrespectful, please report it.)
It will be of a great use if you can add "Create Puzzle" feature to this project. Solver is always gr8 with "Create Feature". This will give it an educational value and importance. Looking forward to future updates ... (If this comment was disrespectful, please report it.)
Hi! Just received your email. Tried to reply to that email; but failed. So came back to this comment area!
I understand your current project is SOLVER; I just suggested that you may think of implementing CREATOR in the same. Doesn't matter if you're planning to implement it as a separate module. Once again, thanks for sharing your quality code.
Best Regards,
Ruturaaj. (If this comment was disrespectful, please report it.)
i give u ***** stars but need to generate new games (If this comment was disrespectful, please report it.)
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2/12/2008 11:56:56 PM: 
