Hi.

Who knows how to solve sudoku is too hard?

For example maybe I solve that in 1 hour, but a professional person solve 15 - 20 minutes.

I have not sample. Please guide simple and clear. (No techniques, I know those, but those are time-consuming) and I use of those if necessary. In fact, I would like to learn fast method to solve./Avina

## Difficult Sudoku

### Re: Difficult Sudoku

I'm not one of the really fast ones on this board, but I can get things rolling.

1) Many beginners at Sudoku don't strike a good balance on how much information to notate (putting little numbers in cells to indicate possibilities and so forth). If you notate everything for every cell, it takes forever and you end up with so many little numbers written everywhere that no important information stands out from the crowd. On the other hand, you don't want to do everything in your head. If you have a pair (for example, two cells that must be a 6 and an 8, but you don't know which is which) it's pretty much always worth noting that. If you know what row or column a digit is in for a particular block, that's often worth noting.

2) The key to doing Sudoku efficiently is to get a feel for the flow of the puzzle, especially in hand-designed Sudoku. That means using the geometry of the puzzle to decide what to focus on. The obvious example is that if a row, column or block has rather a lot of known information, it's worth looking at what's left over. Or if you already know where most of the 7's in the puzzle are, figuring out where the rest go. But there are more subtle examples. One easy example of what I'm talking about: suppose the center block has a 1,2,3, and 4 in the four corners (in some order). Suppose there is a 5 in the center row of one of the side blocks to the left or right of the center block. That will force the 5 to be in one of two possible blocks in the center, and furthermore they are in the same column, which may tell us a lot about where the 5's go directly above and below the center. That sort of configuration occurs in more subtle ways as well, but I think provides an obvious example of the geometry of a puzzle drawing your attention.

3) Probably the best way to see how solving a Sudoku quickly works is to watch somebody who is good at it. Look at the videos Thomas Snyder has posted on Youtube of how he solves Sudoku. He's one of the very best in the world, and he explains the logic clearly. Pay attention to what he's looking for and how he's writing down information.

1) Many beginners at Sudoku don't strike a good balance on how much information to notate (putting little numbers in cells to indicate possibilities and so forth). If you notate everything for every cell, it takes forever and you end up with so many little numbers written everywhere that no important information stands out from the crowd. On the other hand, you don't want to do everything in your head. If you have a pair (for example, two cells that must be a 6 and an 8, but you don't know which is which) it's pretty much always worth noting that. If you know what row or column a digit is in for a particular block, that's often worth noting.

2) The key to doing Sudoku efficiently is to get a feel for the flow of the puzzle, especially in hand-designed Sudoku. That means using the geometry of the puzzle to decide what to focus on. The obvious example is that if a row, column or block has rather a lot of known information, it's worth looking at what's left over. Or if you already know where most of the 7's in the puzzle are, figuring out where the rest go. But there are more subtle examples. One easy example of what I'm talking about: suppose the center block has a 1,2,3, and 4 in the four corners (in some order). Suppose there is a 5 in the center row of one of the side blocks to the left or right of the center block. That will force the 5 to be in one of two possible blocks in the center, and furthermore they are in the same column, which may tell us a lot about where the 5's go directly above and below the center. That sort of configuration occurs in more subtle ways as well, but I think provides an obvious example of the geometry of a puzzle drawing your attention.

3) Probably the best way to see how solving a Sudoku quickly works is to watch somebody who is good at it. Look at the videos Thomas Snyder has posted on Youtube of how he solves Sudoku. He's one of the very best in the world, and he explains the logic clearly. Pay attention to what he's looking for and how he's writing down information.

### Re: Difficult Sudoku

Thank you. I would like to know the other player's idea.

### Re: Difficult Sudoku

I think there is no short-cut to solving hard or easy sudoku. There is just one kind of logic to that game. I think the point is to stay clear-headed and make sure you don't miss out any numbers. One time I was trying to solve a "hard" sudoku puzzle at 2AM after a long day at work, after a while I became frustrated as hell cuz of ONE key number that I couldnt work out. I left it there to go to bed. Next morning I glanced at it again and voi-là! The answer was so clear and obvious I wasn't quite sure what was wrong with me the day before. Probably sleepiness

Last edited by AlexHM on Tue 03 Feb, 2015 1:35 am, edited 1 time in total.

### Re: Difficult Sudoku

Of course, every body should know that what time in day or night is possible for solving, studying, ... .

Centralization and think for solving need to relaxation.

### Re: Difficult Sudoku

i don't understand how is it. sometimes you need just one look and everything is clear an sometimes hours are not enough