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Puzzle 10/04/04 (B)

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daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Sun Apr 04, 2010 4:37 pm Post subject: Puzzle 10/04/04 (B)

Code:

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

Play this puzzle online at the Daily Sudoku site

tlanglet

Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

Posted: Mon Apr 05, 2010 1:49 pm Post subject:

One step which is like a xyz-wing but with additions.

Code:

*--------------------------------------------------------------------*
| 9 18 4 | 2 5 3 | 178 6 17 |
| 2 7 6 | 1489 1489 189 | 5 3 149 |
| 5 3 18 | 7 149 6 | 1489 14 2 |
|----------------------+----------------------+----------------------|
| 7 1249 1239 | 1389 1289 1289 | 124 5 6 |
| 6 1249 1239 | 139 129 5 | 1247 8 147 |
| 8 12 5 | 6 7 4 | 12 9 3 |
|----------------------+----------------------+----------------------|
| 1 2689 289 | 489 24689 289 | 3 7 5 |
| 4 5 89 | 189 3 7 | 6 2 19 |
| 3 269 7 | 5 1269 129 | 149 14 8 |
*--------------------------------------------------------------------*

Look at the 149 in r2c9:
If r2c9=1; r1c79|r3c7<>1,
If r2c9=4, then r3c8=1; r1c79|r3c7<>1,
If r2c9=9, then r8c9=1, then r9c8<>1, then r3c8=1; r1c79|r3c7<>1.

Ted

peterj

Joined: 26 Mar 2010
Posts: 974
Location: London, UK

Posted: Mon Apr 05, 2010 2:33 pm Post subject:

Neat! Is it vald to think of this as pincer transport? The xyz-wing (149) vertex at r2c9 with pincers at r3c8 and r8c9 would normally just take out the 1 in r1c9. But the strong link r9c8(1)=r3c8(1) extends r8c9 back into the house taking out all the other 1s??

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Mon Apr 05, 2010 3:56 pm Post subject:

I played three moves. The XYZ, an XY-Wing (891) and take your choice, an M-Wing (49) or XY-Wing (491).

daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Mon Apr 05, 2010 5:04 pm Post subject:

peterj wrote:

Neat!

Is it vald to think of this as pincer transport? The xyz-wing (149) vertex at r2c9 with pincers at r3c8 and r8c9 would normally just take out the 1 in r1c9. But the strong link r9c8(1)=r3c8(1) extends r8c9 back into the house taking out all the other 1s??

Not quite. Your approach is similar to Ted's, but you didn't account for r2c9=4 producing the eliminations in <1> as well.

tlanglet

Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

Posted: Tue Apr 06, 2010 12:14 am Post subject:

peterj wrote:

I have recently been looking at the similarities between a xyz-wing and a finned xy-wing and posted a new thread here to provide an example. In fact, I found the step for this puzzle while looking for a finned xy-wing condition.

As a finned xy-wing with vertex 49 in r2c9, the only deletion provided by the xy-wing is the 1 on r1c9; the fin 1 in r2c9 will also make that same deletion.

However, when viewed as an xy-wing I believe that the transport of the 1 in r8c9 to r3c8 is valid, resulting in a 1 in either r2c9 or r3c8 thereby deleting the all of the other 1s in box3.

In my original post I presented the step like a xyz-wing simply because I thought it would be less confusing,

Ted

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Tue Apr 06, 2010 1:04 am Post subject:

Quote:

As a finned xy-wing with vertex 49 in r2c9, the only deletion provided by the xy-wing is the 1 on r1c9;

Why not r9c8 as well?

peterj

Joined: 26 Mar 2010
Posts: 974
Location: London, UK

Posted: Tue Apr 06, 2010 10:41 am Post subject:

daj95376 wrote:

peterj wrote:

Not quite. Your approach is similar to Ted's, but you didn't account for r2c9=4 producing the eliminations in <1> as well.

The case r2c9=4 potentially eliminating all 1s in block 3 is surely part of the standard xyz-wing i.e. the pincer in the same block as the vertex? The added eliminations come from the logic around the pincer outside the house forcing r3c8 to also be 1.

tlanglet

Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

Posted: Tue Apr 06, 2010 11:26 am Post subject:

Marty R. wrote:

Quote:

As a finned xy-wing with vertex 49 in r2c9, the only deletion provided by the xy-wing is the 1 on r1c9;

Why not r9c8 as well?

Marty,

The xy-wing would delete 1 from r9c8, but if the fin is true, r2c9=1, then it does not directly "see" r9c8, and if the fin is transported, (1)r2c9 - r3c8 = r9c8, so that it can not be deleted.

Ted

daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Tue Apr 06, 2010 4:28 pm Post subject:

peterj wrote:

Yes, I must have been very tired to have not realized it. Sorry!

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