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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sat Aug 23, 2008 7:13 am Post subject: competition AUG 22 |
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| Code: | . . 9|6 . 3|. . .
2 . .|1 . 4|6 . .
. 3 .|. 2 .|. . .
-----+-----+-----
. 1 2|. . .|7 . .
6 . .|7 . 8|. . 5
. . 8|. . .|9 6 .
-----+-----+-----
. . .|. 7 .|. 5 .
. . 1|8 . 2|. . 7
. . .|4 . 6|3 . . |
| Code: | .------------------.------------------.------------------.
| 147 47 9 | 6 8 3 | 5 1247 124 |
| 2 578 57 | 1 9 4 | 6 378 38 |
| 148 3 6 | 5 2 7 | 18 148 9 |
:------------------+------------------+------------------:
| 345 1 2 | 39 6 59 | 7 348 348 |
| 6 9 34 | 7 134 8 | 12 1234 5 |
| 3457 457 8 | 2 134 15 | 9 6 134 |
:------------------+------------------+------------------:
| 348 248 34 | 39 7 19 | 128 5 6 |
| 35 6 1 | 8 35 2 | 4 9 7 |
| 9 2578 57 | 4 15 6 | 3 128 128 |
'------------------'------------------'------------------' |
last week's competition puzzles were dissapointing, but this one makes up for it. if you don't like xy-chains, this will prove worthy. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sat Aug 23, 2008 4:20 pm Post subject: |
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I guess this is another example of a useful useless technique.
In rows 4,8 is a Skyscraper in <5> that does not produce eliminations. However, the end cells each see a <15> cell, and the resulting eliminations in <1> crack the puzzle. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Sat Aug 23, 2008 8:50 pm Post subject: |
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Nice catch, Danny.
Welcome in my nursing home  |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Sat Aug 23, 2008 10:54 pm Post subject: |
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| It could be called a 15 W-Wing where the external strong link is provided by the Skyscraper. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Aug 24, 2008 7:36 am Post subject: |
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Ravel,
are you ending your posting career on this site at 999 posts?? |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Aug 24, 2008 2:28 pm Post subject: |
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My brute force approach involved a:
x-wing on <9>,
skyscraper on <3>,
finned x-wing on<4>,
x-wing on <8>,
Type 4 UR on <57>,
skyscraper on <4>, and finally
a xy-wing on <345>!
It is hard to believe that all those moves directly contributed to the solution.
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sun Aug 24, 2008 3:22 pm Post subject: |
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There is a UR 57 in r29c23 with strong links.
The strong link on 5 in r2 removes 7 from r9c2, the strong link (7) in r9 removes 5 from r2c2.
With the 5 gone from r2c2, there is now a strong link on 5 in col 2 and the w-wing (1) r6c6=r9c5. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sun Aug 24, 2008 9:46 pm Post subject: |
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| Quote: | | There is a UR 57 in r29c23 with strong links. |
I found the skyscraper, an ER on <8> and the x-wing. But for the life of me I can't see the UR on 57 because I have more than two 5's and two 7's in C2. (i.e. there ain't no strong link).  |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Aug 25, 2008 4:43 am Post subject: |
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| cgordon wrote: | | Quote: | | There is a UR 57 in r29c23 with strong links. |
I found the skyscraper, an ER on <8> and the x-wing. But for the life of me I can't see the UR on 57 because I have more than two 5's and two 7's in C2. (i.e. there ain't no strong link). |
Craig, I did not have any strong links in col2, but row2 has a strong link on <5> which allows the deletion of <7> in r9c2. Also, a strong link on <7> in row9 deletes <5> from r2c2.
Ted |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Aug 25, 2008 1:20 pm Post subject: |
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Ted: This is an interesting revelation for me. My understanding of Type 4 UR's had been that the strong link had to be on the multi-numbered cells which were NOT the pairs - eg in this case the 578's.
Cheers, Craig
| Code: |
+--------+-------+-------+
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
+--------+-------+-------+
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Aug 25, 2008 1:42 pm Post subject: |
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| cgordon wrote: | Ted: This is an interesting revelation for me. My understanding of Type 4 UR's had been that the strong link had to be on the multi-numbered cells which were NOT the pairs - eg in this case the 578's.
Cheers, Craig
| Code: |
+--------+-------+-------+
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
+--------+-------+-------+
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Craig, you are right about the type 4. This is not a type 4 and I have not yet found a suitable and universally accepted name for these babies. I ended up calling it "UR with strong link", see this thread |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Aug 25, 2008 1:48 pm Post subject: |
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| cgordon wrote: | Ted: This is an interesting revelation for me. My understanding of Type 4 UR's had been that the strong link had to be on the multi-numbered cells which were NOT the pairs - eg in this case the 578's.
Cheers, Craig
| Code: |
+--------+-------+-------+
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
+--------+-------+-------+
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Craig, I believe the code above is a Type 2 UR; any other <8s> in col2 may be removed.
After I sent my previous response to you, I noticed the prior comments by Nataraj; he had already noted the two possible deletions.
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Aug 25, 2008 3:21 pm Post subject: |
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| nataraj wrote: | | you are right about the type 4. |
I should have added: insofar as there must be a strong link between the two multi-valued cells. The pattern is slightly different from yours, as Ted has pointed out:
| Code: |
type 4:
+----- no other 7 in col 2 => remove 5 from both r29c2
v
+--------+-------+-------+
| . . . | . . . | . . . |
| .579 57| . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+--------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| .578 57| . . . | . . . |
+--------+-------+-------+
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Aug 25, 2008 3:47 pm Post subject: |
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I'm familiar with the Type 4 as shown in Nataraj's example above - and the Type 2's as shown in Ted's example which removes any other 8's from C2 (though at my stage I had no others). However, this is the first time I've seen the animal which has no name. Still not sure I follow it. Is there a "rote" rule or procedure?
I've mentioned before that I believe the diagonal variant of Type 4's should be a Type 6. Maybe this should be a Type 7.
Cheers |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Aug 25, 2008 5:08 pm Post subject: |
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I assume the (57) UR discussions are based on this PM:
| Code: | +-----------------------------------------------------+
| 147 47 9 | 6 8 3 | 5 27 12 |
| 2 578 57 | 1 9 4 | 6 378 38 |
| 18 3 6 | 5 2 7 | 18 4 9 |
|-----------------+-----------------+-----------------|
| 45 1 2 | 39 6 59 | 7 38 348 |
| 6 9 3 | 7 4 8 | 2 1 5 |
| 457 457 8 | 2 13 15 | 9 6 34 |
|-----------------+-----------------+-----------------|
| 38 2 4 | 39 7 19 | 18 5 6 |
| 35 6 1 | 8 35 2 | 4 9 7 |
| 9 578 57 | 4 15 6 | 3 28 12 |
+-----------------------------------------------------+
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| Code: | [r9c3]=5 [r2c3]=7 [r2c2]=5 (UR) [r9c2]=8 [r9c8]=2 [r9c9]=1 [r9c5]=5 => [r9c3]<>5
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However, it still doesn't advance the puzzle like ...
| Code: | [XY-Chain]: -5r4c6 9r4c6 1r7c6 8r7c7 3r7c1 5r8c1 => [r4c1]<>5
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon Aug 25, 2008 7:10 pm Post subject: |
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Some more UR eliminations in this grid:
| Code: | +-----------------------------------------------------+
| #147 #47 9 | 6 8 3 | 5 27 12 |
| 2 @578 @57 | 1 9 4 | 6 *378 *38 |
| 18 3 6 | 5 2 7 | 18 4 9 |
|-----------------+-----------------+-----------------|
| 45 1 2 | 39 6 59 | 7 *38 *348 |
| 6 9 3 | 7 4 8 | 2 1 5 |
| #457 #457 8 | 2 13 15 | 9 6 34 |
|-----------------+-----------------+-----------------|
| 38 2 4 | 39 7 19 | 18 5 6 |
| 35 6 1 | 8 35 2 | 4 9 7 |
| 9 @578 @57 | 4 15 6 | 3 28 12 |
+-----------------------------------------------------+ |
As nataraj said, from the UR 57 you can follow r2c2<>5 and r9c2<>7.
Both lead to a deadly pattern 5-7-5-7
r2c2=5 => r2c3=7 => r9c3=5 => (strong link for 7) r9c2=7
r9c2=7 => r9c3=5 => r2c3=7 => (strong link for 5) r2c2=5
UR 38 in r24c89, strong links for 3 in r2 and 8 in r4 (or c9): r2c8<>8, r4c9<>3.
r2c8=8 => r4c8=3 => (strong link for 8) r4c9=8 => r2c9=3
r4c9=3 => r2c9=8 => (strong link for 3) r2c8=3 => r4c8=8
UR 47 in r16c12, strong links for 7 in c1 and r6 and for 4 in r1 and c2: r1c2<>7, r1c1<>4, r6c12<>4
r1c2=7 => (strong links for 4) r1c1=4 and r6c2=4 => r6c1=7
r1c1=4 => (strong link for 7) r6c1=7 and r1c2=7 => (strong link for 4) r6c2=4
r6c1=4 => (strong links for 7) r1c1=7 and r6c2=7 => r1c2=4
r6c2=4 => r1c2=7 => (strong link for 4) r1c1=4 => (strong link for 7) r6c1=7 |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Aug 25, 2008 8:13 pm Post subject: |
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| Quote: | Both lead to a deadly pattern 5-7-5-7
r2c2=5 => r2c3=7 => r9c3=5 => (strong link for 7) r9c2=7
r9c2=7 => r9c3=5 => r2c3=7 => (strong link for 5) r2c2=5
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'ang about !!
Notwithstanding the 2nd line is simply the reverse of the 1st. Why can't r9c2 be an <8>. In fact it has to be an <8> since there are no others left in c2.
Also solution suggest two strong links are needed fot this process (unlike Type 4s). |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Aug 26, 2008 2:57 am Post subject: |
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| ravel wrote: | Some more UR eliminations in this grid:
As nataraj said, from the UR 57 you can follow r2c2<>5 and r9c2<>7.
UR 38 in r24c89, strong links for 3 in r2 and 8 in r4 (or c9): r2c8<>8 ...
UR 47 in r16c12, strong links for 7 in c1 and r6 and for 4 in r1 and c2: ... |
I found the (57) UR and the (38_) UR, but they didn't contribute much to solving the puzzle, so I ignored them. I even found the (47) UR, but missed its eliminations  . I'm glad to see that you haven't let your skills atrophy while in your nursing home.  |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Aug 26, 2008 6:18 am Post subject: |
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| cgordon wrote: | | Quote: | Both lead to a deadly pattern 5-7-5-7
r2c2=5 => r2c3=7 => r9c3=5 => (strong link for 7) r9c2=7
r9c2=7 => r9c3=5 => r2c3=7 => (strong link for 5) r2c2=5
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'ang about !!
Notwithstanding the 2nd line is simply the reverse of the 1st. Why can't r9c2 be an <8>. In fact it has to be an <8> since there are no others left in c2.
Also solution suggest two strong links are needed fot this process (unlike Type 4s). |
I will try to explain:
2nd line is not "simply" the reverse of line 1. With implications ("if a, then b") one must always be most careful about the direction: "if poisoned, people die" is not the same or the reverse of "if people die they are poisoned".
Why can't r9c2 be 8? The two statements say nothing about 8, only about 5 and 7. But I can see where you got that impression, let's look more closely:
There are two individual eliminations here, and they should be looked at separately.
Start with the first line.
It says that if r2c2=5 then a deadly pattern results, the puzzle has at least 2 solutions. Since the creator of the puzzle supposedly guarantees that his puzzles are unique, the assumption (r2c2=5) leads to a contradiction and must therefore be false.
It may look like the result of line one is r9c2=7 but that is not the case. The result of line one is r2c2 <> 5 !
Same with line 2: if r9c2 were 7 then a deadly pattern results, thus r9c2<>7.
In both cases, the strong link in the other DP candidate was essential for the elimination.
In line 1, the strong link (7) in r9 helped remove 5 from r2c2.
In line 2, the strong link (5) in r2 helped remove 7 from r9c2.
| Quote: | Is there a "rote" rule or procedure?
|
Yes.
In short, the procedure is:
When there is a type 3 UR, look for a strong link in one of the two DP candidates.
Strong link parallel to the "floor cells" -> type 4
Strong link perpendicular: that's what I call  a "straight weasel".
For a description see the link I posted above (to the solving techniques section). |
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