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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Sun Mar 08, 2009 10:51 am Post subject: Set Q Puzzle 31 |
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| Code: | +-----------------------+
| . . . | 8 . 2 | . . . |
| . . . | . . 7 | . 9 1 |
| . . 8 | . 1 . | . . . |
|-------+-------+-------|
| 3 . . | 2 . 5 | 9 8 . |
| . . 5 | . . . | . . 3 |
| 8 9 . | 4 . 3 | 1 . 7 |
|-------+-------+-------|
| . . . | 5 . 1 | 7 . 8 |
| . 2 . | 7 . . | . . . |
| . 8 . | . 9 4 | 2 . . |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Mar 10, 2009 12:13 am Post subject: |
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| Code: | .---------------------.---------------------.---------------------.
| 1479 13457 379 | 8 45 2 | 35 467 46 |
| 2 456 46 | 3 45 7 | 8 9 1 |
| 47 35 8 | 9 1 6 | 35 47 2 |
:---------------------+---------------------+---------------------:
| 3 146 146 | 2 7 5 | 9 8 46 |
| 467 467 5 | 1 8 9 | 46 2 3 |
| 8 9 2 | 4 6 3 | 1 5 7 |
:---------------------+---------------------+---------------------:
| 469 346 39 | 5 2 1 | 7 346 8 |
| 5 2 146 | 7 3 8 | 46 146 9 |
| 17 8 37 | 6 9 4 | 2 13 5 |
'---------------------'---------------------'---------------------' |
another fiesty one
UR {3,5}
(1=7)r9c1 - (7)r9c3 = (7-9)r1c3 = (9)r1c1; r1c1 <> 1
(6)... r4c2 = r5c1 - r5c7 = r8c7 - r8c3 = r2c3; r2c2 <> 6 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Mar 10, 2009 4:40 am Post subject: |
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| Type 1 UR (35), Hidden UR (45), W-Wing (17), Hidden UR (47) and Remote Pairs (46). |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Mar 10, 2009 3:27 pm Post subject: |
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Three steps (assuming the last one is correct):
skyscraper <6> in r5c17,
xy-wing <147> with pivot <17> in r9c1,
6-cell DP <46> in r1c89, box 6, and r8c78; r8c8=1 to prevent DP and solve the puzzle.
Ted  |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Mar 10, 2009 3:47 pm Post subject: |
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[Withdrawn: way in over my head!]
Last edited by daj95376 on Tue Mar 10, 2009 9:55 pm; edited 1 time in total |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Mar 10, 2009 4:27 pm Post subject: |
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| daj95376 wrote: | | tlanglet wrote: | Three steps (assuming the last one is correct):
skyscraper <6> in r5c17,
xy-wing <147> with pivot <17> in r9c1,
6-cell DP <46> in r1c89, box 6, and r8c78; r8c8=1 to prevent DP and solve the puzzle.
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You forgot to consider the <7> in [r1c8] for the DP. (I think?)
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Danny, given what I posted you are correct! What I (again) forgot to include was a transport of the xy-wing pincer at r8c3 to r7c8 via r7c2 that deletes <4> from r3c8 making it a <7> thereby deleting the 7 in r1c8 so that this is like a Type 1 DP. This is the second time recently that I failed to include a transport in my post. Sorry......
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Mar 10, 2009 6:39 pm Post subject: |
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Ted: It turns out that we are both incorrect. RonK sent me this message in another forum.
The following is NOT a deadly pattern.
| Code: | . . . | . 46 46
. . . | . . .
. . . | . . .
---------+----------
. . . | . . 46
. . . | 46 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 46 .
. . . | . . .
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These are ...
| Code: | . . . | . 46 46
. . . | . . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 . 46
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 46 .
. . . | . . .
. . . | . 46 46
. . . | . . .
. . . | . . .
---------+----------
. 46 . | . . 46
. 46 . | 46 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 46 .
. . . | . . .
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I recall a very old post by Carcul (to me) where he said that the cells of a DP must exist in the same number of rows as columns as boxes.
[Edit: I reinstated this post in order to discuss it below.]
Last edited by daj95376 on Tue Mar 10, 2009 10:45 pm; edited 2 times in total |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Mar 10, 2009 7:13 pm Post subject: |
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| Quote: | | I recall a very old post by Carcul (to me) where he said that the cells of a DP must exist in the same number of rows as columns as boxes. |
How does one apply this statement? In the one you say is not a DP, I see 46s in three rows, three columns and three boxes. Right now, my DPs are limited to two columns, three rows and three boxes, as in the 23-25-35 DP in stack one below.
| Code: | +----------------+----------------+----------------+
| 24 8 7 | 6 9 5 | 12a 3 1-24 |
| 9 5 1 | 23 4 38 | 7 6 28d |
| 234 6 234 | 12 7 18 |-258 9 -245-8|
+----------------+----------------+----------------+
| 7 3 9 | 4 18 6 |-128 5 12-8 |
| 25 1 25 | 7 38 9 | 6 4 38c |
| 8 4 6 | 5 13 2 | 13b 7 9 |
+----------------+----------------+----------------+
| 14 7 8 | 9 6 14 | 35 2 35 |
| 135 9 35 | 13 2 7 | 4 8 6 |
| 6 2 34 | 8 5 34 | 9 1 7 |
+----------------+----------------+----------------+ |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Mar 10, 2009 7:57 pm Post subject: |
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| daj95376 wrote: | Ted: It turns out that we are both incorrect. RonK sent me this message in another forum.
The following is NOT a deadly pattern.
| Code: | . . . | . 46 46
. . . | . . .
. . . | . . .
---------+----------
. . . | . . 46
. . . | 46 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 46 .
. . . | . . .
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Danny, I need to review the literature, but I thought any pattern that would permit two (multiple?) solutions was a deadly pattern. The pattern here has that feature.
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Mar 10, 2009 9:53 pm Post subject: |
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I fully admit that I'm in way over my head when it comes to explaining DPs. I withdrew all of my previous messages and will wait for someone to find an accurate explanation.
My deepest apologies for any inaccuracies in previous statements!  |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Mar 10, 2009 10:20 pm Post subject: |
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| tlanglet wrote: | | daj95376 wrote: | Ted: It turns out that we are both incorrect. RonK sent me this message in another forum.
The following is NOT a deadly pattern.
| Code: | . . . | . 46 46
. . . | . . .
. . . | . . .
---------+----------
. . . | . . 46
. . . | 46 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 46 .
. . . | . . .
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Danny, I need to review the literature, but I thought any pattern that would permit two (multiple?) solutions was a deadly pattern. The pattern here has that feature.
Ted |
This is not that difficult. A DP is self-contained, it does not depend on other cells for its existence. Let's take this:
| Code: | . . . | . 46 46
. . . | . . .
. . . | . . .
---------+----------
. . . | . . 46
. . . | 46 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 46 46 .
. . . | . . .
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The possible solutions are:
| Code: | . . . | . 6 4
. . . | . . .
. . . | . . .
---------+----------
. . . | . . 6
. . . | 4 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 6 4 .
. . . | . . .
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or | Code: | . . . | . 4 6
. . . | . . .
. . . | . . .
---------+----------
. . . | . . 4
. . . | 6 . .
. . . | . . .
---------+----------
. . . | . . .
. . . | 4 6 .
. . . | . . .
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Are there two solutions?
We have interchanged <4> and <6> in R18 and C56 and B258.
We Have NOT interchanged <4> and <6> in two cells each in R4 and R5. This is not a DP.
Keith
[DAJ edit: corrected a typo and removed extraneous quote trailers.] |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Mar 10, 2009 10:56 pm Post subject: |
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I should keep my trap shut, but that wouldn't be me. 
It would appear that RonK's message to me is correct in light of Keith's post above. (Whew!)
I went looking for information on Deadly Pattern, and lost track of the forest for the trees. What I found was that all of the DP examples with just two candidates had the same number of rows/columns/boxes containing the DP cells -- as in my recollection from Carcul. However, there were also DPs with more than two candidates where Carcul's statement is not the case. (Marty: your example falls into this category.)
I'm still only on the fringe of understanding DPs, and I'm still in search of a qualified explanation that doesn't rely on Unavoidable Set.
Regards, Danny |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Wed Mar 11, 2009 1:43 am Post subject: |
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Marty: from your PM ...
| Code: | <2> occurs in two rows/columns/boxes -- [r35 ]/[c13]/[b14 ]
<3> occurs in two rows/columns/boxes -- [r3 8]/[c13]/[b1 7]
<5> occurs in two rows/columns/boxes -- [r 58]/[c13]/[b 47]
+-----------------+
| 24 8 7 |
| 9 5 1 |
| *23+4 6 *23+4 |
+-----------------+
| 7 3 9 |
| *25 1 *25 |
| 8 4 6 |
+-----------------+
| 14 7 8 |
| *35+1 9 *35 |
| 6 2 34 |
+-----------------+
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From doing a cursory examination of the >2 candidate DP examples in Sudopedia, a specific candidate always appeared in the same number of rows/columns/boxes. I don't know if this is a hard-'n-fast rule!
| Sudopedia wrote: | | all deadly patterns of size less than about 30 cells consist entirely of bivalue cells |
Last edited by daj95376 on Wed Mar 11, 2009 1:55 am; edited 1 time in total |
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wapati
Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
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| Posted: Wed Mar 11, 2009 1:44 am Post subject: |
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I liked a sky on 6s, xy-wing 147, and ER on 4s and then one of BUG1 or 4 cell xy-chain 3679.
Fun puzzle, I did it twice 'cause I wanted to see if the 35 UR matters. (not!) |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Mar 11, 2009 3:47 am Post subject: |
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OK Danny, thanks.
| Quote: | | Marty: from your PM ... |
If this means Personal Message, I didn't send one!! Otherwise, I don't know what it stands for. |
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wapati
Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
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| Posted: Wed Mar 11, 2009 4:07 am Post subject: |
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| Marty R. wrote: | OK Danny, thanks.
| Quote: | | Marty: from your PM ... |
If this means Personal Message, I didn't send one!! Otherwise, I don't know what it stands for. |
Pencil Mark.  |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Mar 11, 2009 5:10 am Post subject: |
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| Quote: | | Pencil Mark. |
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