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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Thu Aug 26, 2010 4:30 am Post subject: Puzzle 10/08/26: A |
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| Code: | +-----------------------+
| 5 . . | . . . | 1 . . |
| . . . | . . 9 | . . 6 |
| . . 9 | . 3 4 | . 5 7 |
|-------+-------+-------|
| . . . | . 5 2 | . . . |
| . . 2 | 9 . . | . 1 . |
| . 5 6 | 3 . 1 | . . 2 |
|-------+-------+-------|
| 6 . . | . . . | 2 . 4 |
| . . 8 | . 4 . | . 3 . |
| . 4 1 | . . 3 | 5 . 8 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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JC Van Hay
Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium
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| Posted: Thu Aug 26, 2010 9:25 am Post subject: |
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| Quote: | Grouped Skyscraper on 9 : (9)C27 : => r4c89<>9
XY Wing Style : To avoid DP (67)R15C56 : pseudo-cell[(2)r1c5,(8)r1c6] (87)R7C6 (72)R9C4 : => r13c4,r9c5<>2
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Aug 26, 2010 3:13 pm Post subject: |
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AIC: (7)r5c56=(7)r5c2-(7=3)r4c3-r5c1=r5c7-(3=9)r4c9-(9=7)r6c7; r6c5<>7=8
At this point we have an 8-cell ADP (79)r6789)c1578 marked #
| Code: | *--------------------------------------------------*
| 5 27 34 | 278 267 678 | 1 49 39 |
| 8 17 34 | 5 17 9 | 34 2 6 |
| 12 6 9 | 12 3 4 | 8 5 7 |
|----------------+----------------+----------------|
| 139 19 7 | 4 5 2 | 6 8 39 |
| 34 8 2 | 9 67 67 | 34 1 5 |
| 49 5 6 | 3 8 1 |#79 #479 2 |
|----------------+----------------+----------------|
| 6 3 5 | 178 #179 78 | 2 #79 4 |
|#279 29 8 | 6 4 5 |#79 3 1 |
|#79 4 1 | 27 #279 3 | 5 6 8 |
*--------------------------------------------------* |
To prevent the DP, the external implications are r7c46=7, r9c4=4 & r8c2=9
(7)r7c46; r9c5<>7
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(7)r9c4; r9c5<>7
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(9)r8c2-(9=7)r9c1; r9c5<>7
I was hoping/expecting better results but the single deletion was not needed to complete the puzzle.
Flightless xy-wing -279: (2)r1c45=(2)r3c4-(2=7)r9c4-(7=9)r9c1-(9=2)r8c2; r1c2<>2
Ted |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Thu Aug 26, 2010 3:13 pm Post subject: |
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Two wings..
| Quote: | xy-wing(39-7) r4c9 ; r4c78<>7, r6c1<>7
m-wing(29) ; (2=9)r8c2 - r9c1=(9-2)r9c5=r1c5 ; r1c2<>2 |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Aug 26, 2010 3:21 pm Post subject: |
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| JC Van Hay wrote: | | Quote: | Grouped Skyscraper on 9 : (9)C27 : => r4c89<9> r13c4,r9c5<>2
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JC,
I think your grouped skyscraper can also be called a finned x-wing.
Also, I really like your use of the ADP to form a xy-wing. Cool! 
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Thu Aug 26, 2010 3:51 pm Post subject: |
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| tlanglet wrote: | To prevent the DP, the external implications are r7c46=7, r9c4=7 & r8c2=9
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Hmmm. I don't have any idea how to select external constraints on an 8-cell ADP. However, my gut tells me that r6c1=9 should be included. Maybe not! |
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ronk
Joined: 07 May 2006
Posts: 398
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| Posted: Thu Aug 26, 2010 4:16 pm Post subject: |
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| daj95376 wrote: | | tlanglet wrote: | To prevent the DP, the external implications are r7c46=7, r9c4=7 & r8c2=9
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Hmmm. I don't have any idea how to select external constraints on an 8-cell ADP. However, my gut tells me that r6c1=9 should be included. Maybe not! |
Your "gut" is correct. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Aug 26, 2010 4:54 pm Post subject: |
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Danny & Ron,
You are correct that I missed an implication but it was really r4c9=9 as I was checking the implications in box6. I guess I just got to excited.
As I noted in the original post, the move did not contributed to solving the puzzle. I included it only because it was somewhat different. Given the additional implication, nothing is even deleted. To bad I messed it up.
Ron, I believe I at least correctly identified the ADP.
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Aug 27, 2010 1:29 am Post subject: |
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XY-Wing (397) + pincer transport
XY-Wing (127)
Coloring (9)
BUG+2 or Type 1 UR (67) |
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ronk
Joined: 07 May 2006
Posts: 398
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| Posted: Fri Aug 27, 2010 11:20 am Post subject: |
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| tlanglet wrote: | You are correct that I missed an implication but it was really r4c9=9 as I was checking the implications in box6. I guess I just got too excited.
As I noted in the original post, the move did not contributed to solving the puzzle. I included it only because it was somewhat different. Given the additional implication, nothing is even deleted. Too bad I messed it up.
Ron, I believe I at least correctly identified the ADP. |
Yes Ted, you definitely identified the BUG-Lite+4 correctly. This provides an excellent example of the flexibility one has in choosing the strong inference sets. One may use 1) all naked sets, 2) all hidden sets, or 3) a mix of naked and hidden sets. And when using hidden sets, the external candidates may either be in the row, column or box ... meaning they may be mixed as well.
| Code: |
Using naked sets, at least one of the extra internal candidates must be true. (left image below)
(2)r9c5
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(1)r7c5 - (1=7)r2c5
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(4)r6c8 - (4=9)r6c1 - (9=7)r9c1
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(2)r8c1 - (2=9)r8c2 - (9=7)r9c1 ==> r9c5<>7
Using hidden sets, at least one of the external DP busters must be true. All the hidden sets were chosen as box sets. (right image below)
(7)[r7c46,r9c4]
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(9)r8c2 -------------------------------------------
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(9)r4c9 - (9)r4c12 = (9)r46c1 - (9)r89c1 = (9)r8c12 - (9)r8c7 = (9)r7c8 - (9)r7c5 = (9)r9c5 ==> r9c5<>7
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________ _________
| Code: |
The mixed set scenario is somewhat more difficult to explain, so I hope this image is sufficient. (image below)
(2-7)r8c1 = (7)r9c1
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(9)r6c1 - (9=7)r9c1
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(7)[r7c46,r9c4] ==> r9c5<>7
Note the extra internal candidate is used at 2r8c1, and the hidden set used for (9)r6c78 is in row 6. |
[edit: fixed 2 typos]
________
Last edited by ronk on Thu Sep 09, 2010 10:55 am; 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: Fri Aug 27, 2010 2:26 pm Post subject: |
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Ron,
Thanks tremendously for the wonderful summary on this issue. You also answered the question I had regarding the ability to mix internal/external SIS. Now I need to improve my basic skills in chasing simple inferences as I missed the deletion here.
As you may have noticed, In my original post, I called this pattern an ADP since I still have been unable to find a post providing a definition for BUG-Lite.
Thanks again for taking the time and energy for the feedback.
Ted |
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