## Floundering in the shallows!

Advanced methods and approaches for solving Sudoku puzzles

### Floundering in the shallows!

I'm a beginner and I've got stuck straight away on this easy puzzle. I'm kind of embarassed to even post this, having read your highly technical and culinary sounding discussions about Swordfish, Turbot Fish, and Sardine Sandwiches etc, but I'm keen to get unstuck.

Here is as far as I got:

... .93 ..7
... 861 .2.
.3. .47 81.

..3 ... 7..
.89 735 16.
... ... 5..

.92 .18 .7.
.4. 379 2.1
1.. .52 ...

I found lots of squares in rows 4, 5, and 6, and in column 4, that contained only two possibilities, but couldn't do anything with them. Maybe I should just let them saute for a while?

David
dah069

Posts: 4
Joined: 08 August 2005

David,

My suggestion for you, as a beginner is to first concentrate on a digit which has the most numbers on the puzzle. For example, in the puzzle you sent, there are many digit 3's.
Start there.
Notice that in box 1 and 4 there are already 3's, but in box 7 there are no 3's.

The 3 in box 7 can only be put in one place. It can only be in column 1. It cannot be in row 8 as there is already a three in box 8 in that column, therefore, it can only be in row 7.

Hope this helps,
Hana.
hana somekh

Posts: 28
Joined: 30 July 2005

Thanks Hana - now you've pointed it out, I can't believe I missed it!
Cheers,
David
dah069

Posts: 4
Joined: 08 August 2005

David,

Haha! Yes, I a agree. It's all a bit of a weird cross between star wars and a fish shop.

Cells with two posibilities can sometimes tell you things. If two cells in the same row/column/block have exactly the same two possibilities, then these can be excluded from the other unknown cells in the same row/column/block they are in. In other words, you know what they are, you just don't know what order they are in, and they can't go anywhere else. If that makes sense, which it might not.

Some places call these visible (naked) or hidden pairs. You can extend the logic to triplets or even more, although they become less likely and less useful.

A good explaination of it is here --

http://www.angusj.com/sudoku/hints.php (see naked and hidden pairs)

and my personal explaination here --

http://www.users.bigpond.net.au/sbryan/other/sudoku.html

I think "naked pairs" sounds a lot more appealing than a star wars fish hybrid, don't you?

Regards,
Saul
saulysw

Posts: 4
Joined: 02 August 2005