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Powered by LifeTypeThis is the hardest one I have ever worked on. [Update 10/24/2006: thanks to you all reading this post and posting other links, I have since found more interesting ones -- look through the comments - the one posted on October 9th appears to be pretty hard, though maybe I just made a mistake on it] When we were with my parents last weekend, we found out that my parents are big Suduko fans, and do quite a number of them during the week, in different papers, page-a-day calendars, etc.
Dad was trying to find a hard one for me, and found a "six star" one, that turned out to be not that hard - reasonably difficult, but similar to what I had seen before. We had been trading secrets of how we figure out puzzles the fastest, and he liked one of my starting first-pass rules, but then found a puzzle that using his rule, and then my rule still did not find a single number during the first pass. After that, the only step I know is to start writing down all possibilities, and it is sort of interesting to see how fast you can narrow them down, it is a little too brute force for my taste, and so I am not interested in it as much.
Once you get one number on this puzzle, it is a normal, reasonably difficult sudoku, the trick is getting the first number. So, I would be interested in hearing how long it takes you to get the first number filled in, and if it doesn't take you that long, what is your strategy, because it must be different than mine.
(see my comment on 11/27/2006 for the original puzzle)Edit: Don't read the comments if you are interested in solving the puzzle, wait until after you are done, or at least until after you have found the first square -- which Linda and I probably had the same first square, so that leads me to believe that everyone might have to start at the same point.
I did it!
8,5,9,6,1,2,4,3,7
7,2,3,8,5,4,7,6,9
1,6,4,3,7,9,5,2,8
9,8,6,1,4,7,3,5,2
3,7,5,2,6,8,9,1,4
2,4,1,5,9,3,7,8,6
4,3,2,9,8,1,6,7,5
6,1,7,4,2,5,8,9,3
5,9,8,7,3,6,2,4,1
Which puzzle is that too? I don't see it, but maybe I scanned too quickly.
Also, I assume you mean you did it by hand -- did you see anything interesting - ie. was there one hard square, and then everything else fell into place, or were their multiple "hard" squares? What are your solving methods - do you write out all possibilities right from the start, or do you logically solve "easy" ones first?
I am more interested in the methods than just a simple "did it" comment.
please send me a sudoku puzzle
I came across this puzzle (see the comment about halfway down the page, by 'YH') again, had a photocopy of it lying around somewhere. I haven't done very many sudokus lately, (so might as well start with a hard one, right?)
I actually did much better than I had previously done - I got 8 numbers written in this time, before I plugged it into my favorite sudoku solver. I was happy to see it not find anything I didn't know about, until it got to a new rule, the "hidden unique rectangle" issue, which is an interesting rule, and maybe one I'll be able to keep in my head.
Unfortunately, in this case, it didn't help all that much, just removed one possibility, leaving me stuck again. I was happy to see the solver again not find anything until the "pattern overlay" issue, which I hadn't heard of, and is listed as the hardest issue this particular solver knows how to solve before going to trial and error. Unfortunately, the documentation is being rewritten, and the issue involves looking at 5 squares, none of which are in the same row or column, so too hard for me to guess what the rule is. I'll have to look up the rule elsewhere, and see if I can figure out what it means.
While looking around on his site, I found a Sudoku Song, which is entertaining.
Ah, I should have looked it up before commenting. Pattern overlays are not for humans, at least not when you only have 26 numbers filled in.
I let my solver keep going, and it made a number of guesses to remove certain possibilities before it finally found another number using logic. I am probably not going to continue this puzzle, unless I can find another solver that is as nice as scan raid's to explain how it does it.