2blowhards.com: Computerized Sudoku

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November 30, 2005

Computerized Sudoku

Donald Pittenger writes:

Dear Blowhards --

A while back, Michael posted about Sudoku number-grid puzzles.

Some commenters, me included, are puzzle-averse. And some in the Blowhards community, me included, are computer geeks.

So what could be nicer than to stumble across a computerized Sudoku-solver for puzzle-averse geeks.

All you need to do is download the J computer language from here, hop through some J language tutorials here (tr�s facile, non?) to get the hang of the code, and then peruse this article and key in the computer code as well as an actual Sudoku data array and run the program. Voila!: puzzle solved.

Best of all, you then can use the freed-up Sudoku-solving time to enrich your mind by reading informative and entertaining 2Blowhards postings and comments.

Later,

Donald

posted by Donald at November 30, 2005

Comments

Funny, as a programmer, I decided that I'd right a fairly "dumb" sudoku solver to allow me to concentrate on the all the clever moves necessary to solve a puzzle. The program only used the base rules about non-repetition - no neat tricks.

Unfortunately, I put my first killer sudoku in... and it solved it. I tried with another... it solved it too.

I turned out that none of the puzzles that I had been struggling with required any tricks at all. My failure to solve them was simply not using brute force carefully enough.

That was the end of my sudoku craze.

Posted by: Tom West on December 1, 2005 06:22 AM

So it takes raw brainpower to solve Sudokus? No wonder I'm still struggling. The Michael Blowhard Official Tip for Enjoying Sudoku Puzzles (tm): Stick with the ones rated "Easy."

Posted by: Michael Blowhard on December 1, 2005 10:19 AM

I prefer doing the puzzles out of a book. The intermediate ones when I'm on the train, the harder ones on the couch.

It's nice to nap or otherwise put a puzzle aside, come back to it later and find some answers with a fresh scan.

If they aren't out already, there should be puzzle books with blank grids in the back for those like me who are arrogant enough to use pen and inevitably screw up now and then, so we can take additional stabs.

Posted by: James M on December 1, 2005 11:07 AM

I wrote a straightforward Sudoku solver in Java a year ago. Seems to work in split second for all puzzles that I have found on the web, but don't know how it would work for the really hard ones.

Posted by: Ilkka Kokkarinen on December 1, 2005 11:09 AM

The only Sudoku puzzle I've tried was one from a crossword book that my dad gave me one night. Mildly diverting, up until I found out that it had two solutions.

Posted by: Doug Sundseth on December 1, 2005 11:48 AM

There's something wrong with a puzzle that has two solutions? Damn.

Posted by: Michael Blowhard on December 1, 2005 12:16 PM

In the abstract, I don't think there's anything wrong with a puzzle that has two solutions. The problem was that the puzzle maker seemed not to know that there were two solutions. I was confident enough not to worry much, but a newbie would have come to an impasse: "How do I decide from here? I don't have enough information."

Posted by: Doug Sundseth on December 2, 2005 11:22 AM

There's a relatively simple recursive method for solving sudoku that can solve any sudoku in a few seconds on any computer. (It might take a little longer on an Apple II.) It requires several hundred to several thousand steps, depending on the puzzle.

Writing a program to apply this method took me less than an hour.

What is more interesting is to write a program that can execute the various logical techniques for solving sudoku. A chap I know has done this.

His program is a very elegant interface for doing sudoku (among other things, one can paste into it a digital image of a sudoku, and it will use OCR to read the numeric characters and store them in its sudoku format). It also provides facilities for doing on-screen most of the techniques used by solvers.

And it can apply all the known solving methods, either by executing them or by displaying hints to the user. See

http://www.madoverlord.com/projects/sudoku.t

for the latest version.

Posted by: Rich Rostrom on December 10, 2005 03:14 AM