Sudoku

[Don]

I've been messing around with Sudoku for a while and it's not clear to me how everyone apparently can clear a hard Sudoku in like 3 minutes. One time I tried entering the numbers into a Sudoku solver and it took me 2 minutes just to type the solution in for a top 1% percentile score, and yes technically it might have taken longer if you can just immediately see the solution as opposed to copy the first 20 tiles into a solver but I really doubt people are that good at this. I understand the concept behind Sudoku, and I know people get a lot of practices at it, but I don't see how you can solve these really fast without some kind of written tool. There's a lot of numbers you have to keep track of, and when you're doing it electronically there's no easy way to keep track of them unless you got some writing material on the side.

Now if you can mark the electronic versions square with stuff like 'this square can be 123' I'm sure you can solve it way faster, since once you mark enough of that stuff down you'll see some pretty obvious patterns. I find a lot of the time it's like you'll get say 10 sets of numbers that can either be A or B and then somewhere really further down the chain you can figure out that it has to be A and then it unwinds like 10 boxes and that essentially solves the whole thing, but it's really hard to keep track of multiple chains of pairs or even worse triplets without some kind of visual.

[SineSwiper]

Yeah, I have no idea how to do that sort of thing in any timely manner. It has to be just a certain type of brain that has a really good sense of spacial thinking.

Speaking of mind games, that reminded me of Maven, the perfect Scrabble AI. Of course, writing a perfect Sudoku AI isn't all that hard.

[Kupek]

Why did I do this? As computer security expert Ben Laurie has stated, Sudoku is "a denial of service attack on human intellect". My wife was infected by the virus, and I wanted to convince her that the problem had been solved and didn't need any more of her time. It didn't work for her (although she has since independently kicked the habit), but at least one other person has told me it worked for them, so I've made the world more productive.

Peter Norvig, at the end of his Sudoku solver in 100 lines of Python. (Peter Norvig is, among other things, the director of research at Google.)

For the record, though, I think you're underestimating the kind of skills one acquires after hundreds of hours practicing a task. (And then thousands, and tens of thousands.) Good chess players think of a chess game so differently from you and I that from our perspective, it seems impossible. And, in some ways, it is: if they continued to approach the game as we do, they wouldn't be able to do what they do.

See also: http://en.wikipedia.org/wiki/Chunking_(psychology)

[Don]

I'm sure there are patterns you pick up from after doing something for a long time but if you do the really hard ones (harder than Hard) you basically have to have a mental picture of many pairs of numbers and then follow them far enough to figure out where they unwind. That seems to require something pretty close to photographic memory so I doubt you can get memory like that from just practice. Now if there are tools that lets you mark the stuff electronically you don't need such amazing memories but the online sudoku stuff I found usually don't let you mark the squares with multiple numbers.

If you go by Websudoku (first search for Sudoku), up to Hard you can do it without keeping track of multiple chains of pairs/triples so I can see getting practice speeding up the process greatly. Once you hit Evil or harder, there's no way those are solveable without keeping track of chains as you will physically run out of squares that can be revealed by the simpler methods. They're setup to physically require you to go into a thought process like 'this can only be 3 & 9 which means that can only be 9 & 2 and then that can only be 2 & 3 and (...) and therefore this square has to be a 4'. Now the concept isn't very hard but to keep track of that many chains without losing track of what's going on seems to at least require very special memory techniques as you certainly often have to keep track of more than 7 distinct pieces of information to unwind such a chain.