The New Sudoku Players' Forum

[spamanon]

This was listed as easy, but I beg to differ. I have read all of the techniques on sudoku dragon, but I don't see how any of them apply except the guess and check (labyrinth). Please tell me I am missing something so that I don't have to guess and check! Here is the puzzle as it now stands:

Code: Select all

2 . 6 | . 7 . | 3 4 8
4 7 3 | 6 8 . | . 1 9
. 1 . | 3 . 4 | 7 6 .
------+-------+-----
. 2 . | 7 . 9 | . 3 .
. . . | . 3 . | . 7 .
. 3 . | 5 . 8 | . 9 .
------+-------+-----
. 4 . | 2 1 6 | 9 8 3
1 8 2 | . . 3 | 6 5 7
3 6 9 | 8 5 7 | 1 2 4


I would appreciate it if someone could show me how to deduce logically any next step. Thanks!

Here is the original, so you can see I have done some work:

Code: Select all

2 . 6 | . 7 . | 3 . 8
4 . . | . . . | . . 9
. 1 . | 3 . 4 | . 6 .
------+-------+-----
. 2 . | 7 . 9 | . 3 .
. . . | . . . | . . .
. 3 . | 5 . 8 | . 9 .
------+-------+-----
. 4 . | 2 . 6 | . 8 .
1 . . | . . . | . . 7
3 . 9 | . 5 . | 1 . 4


[Luke]

Hi, spamanon. Really enjoyable puzzle. You mentioned it was listed as "easy" but it's a step above that. With pencil marks your progress probably looks like this:

Code: Select all

 
 *-----------------------------------------------------------*
 | 2     59    6     | 19    7     15    | 3     4     8     |
 | 4     7     3     | 6     8    *25    |*25    1     9     |
 | 589   1     58    | 3    *29    4     | 7     6     25    |
 |-------------------+-------------------+-------------------|
 | 568   2     1458  | 7     46    9     | 458   3     156   |
 | 5689  59    458   | 14    3    12     | 2458  7     256   |
 | 67    3     147   | 5    *246   8     |-24    9     126   |
 |-------------------+-------------------+-------------------|
 | 57    4     57    | 2     1     6     | 9     8     3     |
 | 1     8     2     | 49    49    3     | 6     5     7     |
 | 3     6     9     | 8     5     7     | 1     2     4     |
 *-----------------------------------------------------------*


There are several singles chains like this that will help. They stand out if you "filter" the candidates. Then with all the bivalue cells there will be a few XY chains to move things along.

If you're interested in fish, a finned xwing accomplishes the same elimination shown above. (xwing = r2c67 and r5c67, fin = r5c9.) That opens up an xwing on 2 (r3c59 and r6c59; r5c9<>2.)

[spamanon]

There are several singles chains like this that will help. They stand out if you "filter" the candidates. Then with all the bivalue cells there will be a few XY chains to move things along.

If you're interested in fish, a finned xwing accomplishes the same elimination shown above. (xwing = r2c67 and r5c67, fin = r5c9.) That opens up an xwing on 2 (r3c59 and r6c59; r5c9<>2.)

Thanks for your help, but I don't quite understand the terminology you are using. Where is a good source to find out what a chain, a filter, XY chains are? I do know about the xwings from sudokudragon.


Thanks.

[Pat]

"filtering" means you're only looking at the 2s (or whichever digit seems currently interesting)
hopefully you're using some software which makes "filtering" easy

Mike Barker's great list of solving techniques
or try the SuDoPedia