Su Doku

[Soulstation1]

[Dave James]

I do these all the time, but I'm not very good at it. I think I got one three star puzzle once. My SO's 15 year old daughter, on the other hand, can do whip these out like there's no tomorrow. The degree of difficulty doesn't seem to bother her. Of course, she's a whiz at math. I'm not. These puzzles drive me crazy.

If you're interested, there are hundreds of these that can be downloaded off the net for free. All different difficulty levels. Just Google the word "su doku".

Up over and out.

[Soulstation1]

# 01 Rule

DO NOT USE A PEN

[ejp626]

When I first moved over, I did them every day. Now I just do one a week (Saturday). There really is no math involved, but you do need to be good at working with patterns.

[Soulstation1]

i tried doing a simple one last night for the first time and grew frustrated

this is on the one

http://www.sudokuonline.us/find_puzzle.php...=type&type_id=1

Edited January 17, 2006 by Soulstation1

[Aggie87]

Web Sudoku

No pencil/pen/paper required...

[Soulstation1]

any tips or inside knowlege?

[Soulstation1]

holy cows

i didn't know that each 3 x 3 square must also contain 1-9

Edited January 17, 2006 by Soulstation1

[Quincy]

holy cows

i didn't know that each 3 x 3 square must also contain 1-9

That's a good thing.

Head for the 3 x 3 or line that has the most numbers already filled in. With each blank, check and see the possible numbers that could apply to the square based upon the intersecting lines and 3 x 3 square. You can then in pencil write the possiblities very small and proceed down the the line or in the square. Some people prefer to write what the number can't be. As you proceed further along you'll notice things like there's only one more row/column (in the whole puzzle) that doesn't have a 5 in it or something like that, so you can work on those too.

Developing a system helps. When writing down the possible numbers in a square I always place the 1s, 2s, etc like this:

1 2 3

4 5 6

7 8 9

within the blank square.

Edited January 17, 2006 by Quincy

[ejp626]

There are two general approaches -- which I blend a bit. You start in some square that has a few numbers filled in. You can either pick the first missing number (2) and say, hmm, which of the empty squares can hold 2. Or you can go through all the empty squares and fill in all the possible available numbers. I usually start with the first approach and move towards the second as I fill in things. This helps keep the puzzle slightly less cluttered.

I write the possible numbers really small in the corners, then cross them off as they become unavailable. But I usually don't write down numbers if there are more than three possibilities for a square. I either move to a different 3 x 3 or work on a different number within that 3 x 3.

The important thing is to start recognizing patterns and to look across the entire puzzle. Maybe it helps to think as in chess. A number blocks that same number from appearing in that same row and column, like a rook (sort of). The other thing is that as bits of the puzzle get filled in, you can use incomplete information to fill in elsewhere. So for instance, lets say the grid is like this:

A B C

D E F

G H I

If you can narrow a number down to A or D (because there is something that blocks all the way across G-H-I and there are some other numbers that get in the way), this may be enough to tell you where the same number is placed in the square above or below.

Anyway, it's basically a winnowing process.

[Dave James]

I made up a grid that provides lots of extra space to write in possible numbers. I will also write missing numbers in the margins to the right of the rows and underneath the columns. However, I never write these in until I'm down to no more than three missing numbers in a given row or column.

My opening gambit is to indentify what I call intersections. SS, in the puzzle you reproduced, look at the 5's in the upper left and upper center segments. If you extend those into the upper right segment wher you know you need to have a 5, it eliminates all but two of the boxes. There is another 5 in the lower right hand segment. If you extend that upwards, it takes care of one of those boxes so you know that the 5 can safely be entered in the one remaining box, the one right above the 2. You can usually fill in a fair number of squares using this technique depending, of course, on the level of difficulty. It kind of kick starts the process. After you run out of the slam dunks, that's when the going gets tough.

I've found the more you work on these the more techniques you identify. The biggest problem I have with Su Doko, though, is if you make a mistake, sometimes you don't know it until it comes time to fill in the very last square. That happened to me last night. When it does, you've just wasted a boatload of time and have nothing to show for it. I've tried quitting, but once you get the bug, it's hard to stop. Hmmm. Sounds a bit like another kind of addiction, i.e. the musical one.

Up over and out.

[kulu se mama]

i've found it easiest to fill in the squares where a number has to go (if that makes sense).

i will find 3 - 8's that intersect in a square without an 8, that way i can usually find exactly where that 8 goes.

i will do this for each number, and then i will start looking at which numbers are missing from each block or row.

for some reason i have had much more trouble on the puzzles labeled "easy" or "gentle" than i have had on either moderat or hard puzzles.

i have not attempted a "diabolical" or "evil" puzzle.

[ejp626]

I only did it one time, but I did complete a super Su Doku that was 4 x 4 squares building up to a 16 x 16 puzzle. It can be done, but it took a lot of time and didn't feel all that satisfying (I was bored with it long before I actually finished). I find one a week is just enough.

[Adam]

So the basic idea is to fill them in so that each row, column, and 3x3 box has the numbers 1-9, each number appearing one time only in each row or column or 3x3?

I was in a bookstore in England that had a whole display of Su Doku, and i had never heard of it before.

[Dave James]

Adam,

That's it. Sounds simple. It isn't.

Up over and out.

[DukeCity]

I do these occasionally, and I look at one third of the puzzle at a time. I'm either looking a column of 3x3's, or I'm looking at a row of 3x3's. That gives me enough info to fill in at least a few 'hasta be' squares.

Then I start looking at individual rows and colums to see what's missing, and what might fit where.

Sounds confusing enough, no?

[Nate Dorward]

I must confess I've mostly stiopped doing these puzzles after moving on to the more challenging variant known (in English) as Killer Sudoku (no starting numbers given, just the sums of certain groups of numbers) but if you're looking for solving techniques there are many good spots on the web: this is the one I favour:

http://www.simes.clara.co.uk/programs/sudokutechniques.htm

[Tjazz]

The sudoku calendars are selling for $4. The red box has 365 puzzles. The black box NY Times sudoku has slightly less, because they put one puzzle on sat/sun.

Saw these at Borders.

[couw]

I do these occasionally, and I look at one third of the puzzle at a time. I'm either looking a column of 3x3's, or I'm looking at a row of 3x3's. That gives me enough info to fill in at least a few 'hasta be' squares.

Then I start looking at individual rows and colums to see what's missing, and what might fit where.

Sounds confusing enough, no?

yes very confusing, I look at it all at once, have solved these things in a whiff and was bored shiteless at it.

maybe I should look into Nate's version or spend my time on sensible things like work.