## Puzzle I partly solved, then got totally stuck... help!

Post the puzzle or solving technique that's causing you trouble and someone will help

### Puzzle I partly solved, then got totally stuck... help!

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 84 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 31 8 2 | . . 3 | 6 5 73 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 . 84 . . | . . . | . . 9. 1 . | 3 . 4 | . 6 .------+-------+-----. 2 . | 7 . 9 | . 3 .. . . | . . . | . . .. 3 . | 5 . 8 | . 9 .------+-------+-----. 4 . | 2 . 6 | . 8 .1 . . | . . . | . . 73 . 9 | . 5 . | 1 . 4`
spamanon

Posts: 2
Joined: 03 December 2008

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:
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`  *-----------------------------------------------------------* | 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.)

Luke
2015 Supporter

Posts: 435
Joined: 06 August 2006
Location: Southern Northern California

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.
spamanon

Posts: 2
Joined: 03 December 2008

Pat

Posts: 3639
Joined: 18 July 2005