One of the things I that drove me crazy about Sudoku is how difficult it is to return to a puzzle if you get interupted. This system allows you to walk away from a puzzle at any time and return exactly where you left off.

**Signing Up**

## Step 1: What you need to begin

1. A sudoku puzzle. I enlarged this one (which was the puzzle that appeared on Sudoku.com on July 8, 2006.) to make photography easier. I find this system works better on larger puzzles.

2. A pencil, Not a pen. A pencil.

3. An eraser.

## Step 2: Fill in the "Missing Grid"

Enter the numbers 1 through 9 in a "tic-tac-toe" pattern in every blank box.

## Step 3: Erase "Across"

So the first number (in the upper right corner) is a "6". Erase every other "6" in that row. Once you have completed the erasing, draw a line across the top of the number to indicate that you have cleared out that line.

## Step 4: Erase Down

## Step 5: Erase "All Around"

Now you have eliminated all the sixes from all the other blocks. That indicates that a Six canot appear in any of those blocks.

Keep going, repeat those same three steps for all the other pre-printed numbers in the puzzle.

without thinking is preposterous as the "solution" you give is precisely what we all do when we solve à sudoku ... Exception we do it in our brain and do not write it down.

sorry "except" not "exception"

Difficult to write english without an french auto correct !!!! ;)

Presumably 'broper's somewhat exotic spelling is not for real!

(who is Ible?)

love this system

man pscovio

I'm pretty sure he just means one out of the nine "boxes" in the main grid. I guess if "nona-" is the prefix for "nine", then he'd be talking about a "nonadrant". LOL

I came to this web site hoping to find out where my thinking is muddled when I get down to the same three possible numbers in any box, column, and/or row. I can't seem to figure out how to further eliminate possibilities. If you - or anyone else reading this post - can help, I'll check back!

Thanks!

Granny H

If you just have a place where you have the same three numbers appearing in the same box, column, and row, but there are other bits left to solve as well, try to work on other parts of the puzzle. Somewhere in the puzzle, there's some way to eliminate some of those numbers. You might wind up coming at it from a really backward direction, but it's there.

I think I stated my problem poorly. Let's see ... What I meant was more like what you say in your second paragraph. When I have several "other bits" of the puzzle left here and there, and the same two or three numbers are the only ones available for all of those little boxes, I don't know how to eliminate without guessing. And guessing NEVER works for me! I'll come back again when I bump into a good example to give you.

Again, thanks!

Granny H

How do you soften the puzzle? Select a pattern of rows and columns which have the highest number of digits. Proceed to tackle them in descending order of number of digits.

Once you have selected a row or column with the highest numbers, attack it in an oblique manner. For instance, if you are tackling the upper row, you may find a number repeated in the sub-rows. Now try to fit that number in the 3rd row by looking into the sub-columns.

Attack all 3 horizontal rows and 3 vertical columns turn by turn, systematically in this manner and you would have softened up the puzzle a bit. Repeat the entire process and you'll get a few more discoveries, maybe one or two.

Once the puzzle has become soft, you can start the slog phase. It is NOW that you need a pencil & eraser.

Don't make all entries (from 1-9) in every box. You can straightaway start with the missing numbers ie possibilities.

Once you have entered all possibilities, start looking for singletons - row-wise, column-wise and grid-wise. Having caught singletons, erase the corresponding possibilities row, column and grid wise.

Now look for pairs, triads and even in a few cases, 4-digit patterns. Having identified a pair, triad or a quad in a row/column/grid, proceed to erase the numbers in the remaining possibilities.

Don't forget, once you have discovered any digit, always look obliquely in horizontal as well as vertical directions to fit it into a suitable blank space, as I have described in para 3 above. It helps.

Ultimately you will reach a point where all the solutions cascade into view.

One thing that is the case with most Sudoku puzzles is the symmetry. You notice the symmetry at the start and as the solution proceeds, you will notice a symmetry in the solution. In this case, this is where I agree with Eddie Chong on the "beauty" of the puzzle. What I detest most are those puzzles where you are reduced to guessing (rather than using logic and reasoning) which of 2 or 3 numbers to to choose in 2 or 3 squares and use "trial and error" to solve. This is typical in most Sudoku magazines that have "extreme" or "brutal" puzzles. To me, you should never have to resort to "trial and error" to solve the puzzle. As Sir Arthur Conan Doyle had Sherlock holmes say "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."

good job on you ible but one thing i want to menchon dosint this methoud take the fun out of sudoku? i tryed it on a hard puzzel and i didn't feel like i completed any thing when i was fineshed.

nice way to do it but it takes the fun away

ps

i think the methoud you made is a good one and i have nothing roung with it

it does its job it makes sudoku easy ( :

my dad is always sayin' that it has to be chalenging

Anyone that wants to learn to sudoku should avoid this technique because you will learn nothing by finishing puzzles this way and therefor will never be able to progress on to more challenging puzzles.

This is nott a game of memory, it is a game of systematically solving a grid puzzle.

100% !…

I'm not against cheating, but it's got be worth it. In this example we didn't even try to begin to play sudoku : may as well play pencil and eraser on any piece of paper.

anyway… the example given is so basic that it's not even worth taking the pain to write all those numbers down : this sudoku can nearly be solved by itself !!!…

This is a good way to start if you are learning sudoku, eventually you will learn the patterns and you wont need as many pencil marks. Besides if you are just starting and need this method to solve a puzzle there is little chance that you will know or be able to use the more advanced techniques.

Notice Row-3 has 2 squares whose only values can be 2 or 3. That means if one square is a 2, the other must be a 3. So no other square in that row can have a value of 2 or 3.

Removing all of the 2's and 3's from the other candidates in the row reveals the yellow square to be a 5. That forces the last square in the row to be a 4 and the remaining square in that row to be a 9.

Use this technique and more at http://www.SudokuByZol.com. It has the best pencil mark support of any Sudoku website.

quickly as possible. The uninitiated to this rather 'mechanical' method will be impressed, like I was a moment ago having followed your step by step approach.

I would not, however, resort to this 'protocol' The hallmark of Sudoku puzzles

lie in its intrigue and its beauty as a puzzle to be held in awe, respect and a

challenge to be taken. I often complete the day's puzzle and enjoy my successful

attempt with self satisfaction and look forward to the next day's fresh gauntlet, however long a time it took me. In Sudoku the journey is as enjoyable as its destination.

EddieC

If this method is too tedious for you, try out the many automatic Pencil Mark features at: http://www.SudokuByZol.com

and to the author thanks for the tips.

The fourth column going down.

has 6 numbers

1 3 4 9 2 5

so 6 7 and 8 are missing.

so the box between the 4 and 9 must

cant be a 6 or a 7 so it must be an 8.

blank box.

For fast and efficient pencil mark support and free online sudoku puzzles, try http://www.SudokuByZol.com

Comprehensive and extremely efficient pencil-mark support and user interface.

Play never ending supply of puzzles (5 Levels), or enter your own puzzle using the Solver link or button.

This method will NOT be sufficient to solve 197 of the 200 Sudoku puzzles found in the Extreme Sudoku book by Antoine Alary ( sudoku.alary.org ).

Get that book if you want a real challenge, it even has the pencilmarks pre-printed in half of the puzzles, as most of the advanced Sudoku solving techniques make use of them.

Efficient keyboard or mouse user interface that won't get in your way.

Just click the Solver button or link.

If not - Go to websudoku, click "Evil" and attempt to solve 2,200,342,256, it should appear to be the first one it shows, if not search it. It would be very helpful if anyone is capable of solving this sudoku. Reply to me through my inbox if you have conquered the EVIL SUDOKU.

^{_}o)Unlimited puzzles. Even let's you enter and solve any puzzle from a book or magazine. There are hints and you can print your puzzle to take with you.

Sudoku StrategiesFor a great free online Sudoku experience try Sudoku By Zol: http://www.SudokuByZol.com

Solve as much as the puzzle that you can before it's more difficult. Then fill in the grids for the remaining squares.

Plus, only write the numbers that haven't been eliminated.

Sudoku By Zol makes this easy. For beginners, one click fills all of them in. Advanced users can do it manually.

Let's say two squares in the same row can only be a 3 or a 4. That means you can erase a 3 or a 4 from all other squares in that row's pencil mark values. That further narrows the candidates.

If you don't like all the work of filling in the pencil marks, try http://www.SudokuByZol.com.

Unlimited puzzles with automatic (and manual) pencil mark support. It has the smoothest and most efficient user interface of any Sudoku site out there.

For those without a facebook app. Colorcoded Sudoku

_{,i understand your plight}I am ZoltÃ¡n from Hungary .. but I suppose no one cares about where I write from...

I just want to tell you all that I have a Sudoku solver (by 'have' I mean I did it by myself) and it can be reached here:

http://www.templom.atw.hu

However the program and the website both have a Hungarian language it is not that hard to use it.

If anyone is interested in using it, just write to me an e-mail (templom@atw.hu OR zoltan8905@freemail.hu) and I will make an explanation on how to use it ('cause it has 'hidden' functions).

Anyway, if I get a request I will kindly write it here or just send it in e-mail.

Good luck and great pleasure to You!

Then you erase all the numbers that are dups from each column up and down; works great if you don't make a mistake and think you only have one 2 and overlook the second one so the puzzle goes bad. Or if in erasing you don't erase all the dups of the original number. Other than that works great; 90% of the puzzles solve this way but then again you have the top level of difficult (fiendish, or some such) and you come out with no single number to work off of.

This usually leaves you stuck with a choice of two pairs the same and you have to pick one and go from there, it requires you to make a copy since you just might have picked the wrong one and have to do it with the other choice. I do not like these, not because they are harder but because they don't flow as well. I have tried to find a solution that would let me continue without guessing but even looking at web sites I have not been able to find one that would let me go on. And I do understand that if there are a 6&9, and a 6&9 say in a nine box that right there we have the six and the nine so all other 6&9s in that particular 9-box can be erased. This also works if they are line up in a column either way. And I do know that a 1,6&9, 1,6&9, and a 1,6&9 in a box or column allows all other 1,6&9s to be erased.

But occasionally I wind up with a puzzle that doesn't have even these features and I am stuck---------anybody?

It really does make it easier!

You can solve the above puzzle by following this link:

http://sudokuhelper.kevinpluck.net?g=83f3dcd50b4306951724ee7e0a9b4fb4'

http://sudokuhelper.kevinpluck.net?g=3a70caa2d32282d27ce1cfb455e4ef93

http://sudokuhelper.kevinpluck.net?g=2ea40d2fb5b28c62e72945bdeeb38549

More here http://www.kevinpluck.net/forum/viewforum.php?f=1

Enjoy!

http://www.free-sudoku-games.net (it allows you to get a pdf for the puzzle as well)

got lots of information.

Rubik's Cube = 25 seconds :)

Check it out at http://www.sokudo.be/sudoku

Thanks for the tips though.

One of the tricks that I seem to be employing (quite frequently) is the one you describe.

There is another one where if a number (say 4) has multiple choices within one box and either one row (or column) then you can eliminate that the other boxes in that row (or column).

I like the interface at http://www.zenofsudoku.com. You do not need to be connected :-).. It also has different levels so you can "train". The master level needs a black belt.

When all else fails with the steps above, you still have one more option. I call it "rail" elimination. If, for instance you have a "quadrants" where two (or even three) spaces are empty, but all in the same row:

3 _ 6

2 _ 8

5 _ 1

Then you can deduce that all other spaces in the row in the other quadrants will NOT have those numbers still missing from the first quadrant. This can help in situations like this:

1 2 3 _ _ 6

_ _ 6 7 _ 9 <== rail for 4 & 5

7 8 9 1 2 3

You know that 4 or 5 then can't be in the middle of the second quadrant, and so it must be 8. This sounds intuitive, but my app had to explicitly be told to do this.

HOWEVER, evem with this addition, the app still can't solve level 5 sudoku without educated guessing.

Here's the link to the app on my website:

www.getpoorquickscheme.com/Sudoku.exe

(I can put source code up too if someone wants to see it)

Prep work:

1. Write down all the numbers up to 10

^{64. }2. Cross out any that contain zeroes.

3. Transfer each number into a blank Sudoku puzzle. Cross out any number that doesn't constitute a valid solution.

4. You now have the master list of Sudoku puzzles.

You may want to make a couple photocopies of this so that you can use one list for each puzzle you do. Make sure the copier has at least 10

^{59 or so sheets of paper when you start - you don't want to run out half way through the job! Or you can just use a pencil when crossing out the numbers.}Solving a puzzle:

1. Cross out any numbers off the list that don't match the puzzle you're looking at.

2. At the end, you should be left with one number - that's the solution!

If there's more than one number, either you screwed up or whoever made the puzzle did. You should do all the steps again to make sure.

The use of the notepad may well be outside of the spirit of the Sudoku, I cannot say. I can say that the act of keeping notes will not solve the puzzles by itself - the user must work through the necessary logic and intricasies to find the solution.

So my note pad is really simply a piece of paper to make notes on -- that because my memory could not keep up with the combinations of numbers I was trying to keep straight. Let me reiterate that the act of making notes will not remove the burden of solving the puzzle. It is easy to make mistakes and then mark them down. Those mistakes then become the foundation of solutions that do not work. To those of you who can resolve the puzzles without making notes, my kudos!

For example, one will not be able to solve this puzzle:

http://www.scanraid.com/sudoku.htm?bd=620401030154008076003600401002547169475100382900823040008004600040900010000700054

Using the method described above.

The Sudoku solves this link will take you to cannot even solve it and yet there is a logically determined move one can make to solve the puzzle. And, no, I won't tell you what it is.

For many excellent strategies one might have to employ to solve a Sudoku puzzle, you can check here:

http://www.scanraid.com/BasicStrategies.htm#NP

and other sites found via google.

Basically, this person who wrote:

"It's so easy, you don't even have to think!"

doesn't even have a remote clue what they are talking about.

Sure, if you want to solve sudokus fast, you need to become good at recognizing which strategies are more likely to work, which is some form of pattern-matching/intuition, but for the simple act of solving, all you need is a sufficiently powerful set of strategies and the willingness to spend a bit of time.*

The note pad is here: http://www.cicada.com/pdf/sudoku.pdf

If these instructions do not make sense, leave a note here over the next couple of days; and I'll see if I can fill in any gaps.

Examine each of the marked cells in a (row, column, box): if there are two numbers that only appear in two of the boxes, then you know that those two boxes can only have those two numbers.

Example: If one row has 4567, 4589, 6789, and 6789 left, then the leftmost can only be 45, and the rightmost, by process of elimination, can only be 89.

More rarely, you can find the same rule works for 3-way and 4-way groups.

Another trick: When scanning a row or column, and you find that a number only appears in one box within that row, you can eliminate that number from all other cells in that box. Conversely, when scanning a box, if a number appears in just one column (or row), you can eliminate that number from the other boxes that that column or row passes through.

At the hardest levels, you will find you DO have to guess between sets of possible results. A badly-created puzzle will have multiple solutions (tsk tsk), but most of the time you will need to test an assumption *carefully* such as circling the ones you *think* might be right, and putting tick-marks above the numbers that the circled numbers then rule out. Don't erase anything will testing assumptions, because it's very hard to backtrack.