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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Tue Dec 29, 2020 4:41 pm Post subject: VH (+?) 122920 |
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Hello all, enjoy the puzzle...
Code: |
+-------+-------+-------+
| . . . | . 8 . | 7 . . |
| . 5 1 | 7 3 . | 2 . . |
| . . . | 9 . 6 | . 1 8 |
+-------+-------+-------+
| . . . | . . . | 5 . . |
| 2 4 . | 5 6 . | . . 1 |
| . . 5 | . 4 . | 9 6 . |
+-------+-------+-------+
| 4 . . | 1 . . | . 5 . |
| . 1 . | . 2 . | . 4 . |
| 5 . 7 | . 9 . | . . . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
cheers...immp |
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ZeroAssoluto
Joined: 05 Feb 2017 Posts: 872 Location: Rimini, Italy
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Posted: Tue Dec 29, 2020 7:42 pm Post subject: |
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Hi everyone,
Code: |
+-------------+----------+-----------+
| 6 9 4 | 2 8 1 | 7 3 5 |
| 8 5 1 | 7 3 4 | 2 9 6 |
| 37 237 23 | 9 5 6 | 4 1 8 |
+-------------+----------+-----------+
| 379 378 6 | 38 1 279 | 5 278 4 |
| 2 4 389 | 5 6 79 | 38 78 1 |
| 1 378 5 | 38 4 27 | 9 6 23 |
+-------------+----------+-----------+
| 4 238 238 | 1 7 38 | 6 5 9 |
| 39 1 389 | 6 2 5 | 38 4 7 |
| 5 6 7 | 4 9 38 | 1 28 23 |
+-------------+----------+-----------+
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Play this puzzle online at the Daily Sudoku site
WXYZ-Wing 2,3,7,8 in r5c78,r6c69 and -7 in r5c6
Ciao Gianni |
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TomC
Joined: 30 Oct 2020 Posts: 349 Location: Wales
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Posted: Wed Dec 30, 2020 10:06 am Post subject: |
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Hi Gianni,
My solution, not as elegant though!
Eliminate the 7 in r4c1 to avoid UR of 38 in r46c24
Then eliminate the 8 in r8c3 to avoid UR of 23 in r37c23
Tom |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Wed Dec 30, 2020 10:58 pm Post subject: |
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Nicely done Gianni! I lacked confidence in using the WXYZ pattern here. Too many overlapping candidates it seemed. I was somehow uncomfortable with it. But I did use two forms of Rectangle, one Hidden, one Empty. |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Wed Dec 30, 2020 11:03 pm Post subject: |
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First step was a Hidden Rectangle (23) r37c23 with r7c2<>3.
That takes us here...
Code: |
+-------------+----------+-----------+
| 6 9 4 | 2 8 1 | 7 3 5 |
| 8 5 1 | 7 3 4 | 2 9 6 |
| 37 237 23 | 9 5 6 | 4 1 8 |
+-------------+----------+-----------+
| 379 378 6 | 38 1 279 | 5 278 4 |
| 2 4 389 | 5 6 79 | 38 78 1 |
| 1 378 5 | 38 4 27 | 9 6 23 |
+-------------+----------+-----------+
| 4 28 238 | 1 7 38 | 6 5 9 |
| 39 1 389 | 6 2 5 | 38 4 7 |
| 5 6 7 | 4 9 38 | 1 28 23 |
+-------------+----------+-----------+
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Play this puzzle online at the Daily Sudoku site |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Wed Dec 30, 2020 11:06 pm Post subject: |
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The second step was the Empty Rectangle on (3) r58c7 with boxes 4 and 7.
r5c3<>3.
cheers...immp |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Wed Dec 30, 2020 11:10 pm Post subject: |
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Yes TomC, yours works nicely as well. |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Thu Dec 31, 2020 3:14 pm Post subject: |
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I am thinking that there are interesting boxes here as well for the candidate (3). They would be boxes 4, 6, 7, and 9. These form a rectangle, as keith had suggested in a previous post, applied to a previous puzzle. After identifying any strong links on 3, it appears that, in the second grid, the cells of r7c3 and r5c7 would act as pincers on (3), thus making the same elimination as the Empty Rectangle; r5c3<>3. I am hoping my logic is correct and sound. Please let me know if I am wrong in my application of this. Thank you all.
cheers...immp |
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keith
Joined: 19 Sep 2005 Posts: 3355 Location: near Detroit, Michigan, USA
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Posted: Sun Jan 03, 2021 1:15 am Post subject: |
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immpy,
Thank you for making my New Year!
First, let me say you are correct. Given the Hidden Rectangle elimination, you have pointed out the links that make the elimination of 3 in r5c3.
I had to stare at the Hidden Rectangle for a while, but then I recognized it as a UR overlaid on a X-wing. That is something I can claim to have discovered just about 15 years ago! The original discussion is here:
http://forum.enjoysudoku.com/uniqueness-type-6-ur-meets-x-wing-t3709.html
I'll post a more detailed discussion of this puzzle in a while. First, I need to think about my assertion about "interesting" boxes and how it applies to Empty Rectangles.
Keith |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Sun Jan 03, 2021 4:42 pm Post subject: |
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Thanks Keith. I have identified countless UR types in puzzles, but always had trouble with the specifics. Which type (of 6) was it? The Hidden Rectangle always afforded me the opportunity to make the correct elimination (if any) in the proper cell. I rely on it a lot. It is indeed a UR overlaid on an X-Wing. Most harder puzzles don't feature a simple Type 1 or Type 2 UR. They are complicated by extra candidates in various component cells of the UR. Rarely do they solve in one step, but many times, as in this case, they make a key elimination of a candidate.
The presence of interesting boxes is truly beautiful. I was able to identify one in the most recent VH daily. They seem to be present quite a bit. That is a very good thing! Looking at puzzles in a whole new light now.
cheers...immp |
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immpy
Joined: 06 May 2017 Posts: 570
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Posted: Sun Jan 03, 2021 4:57 pm Post subject: |
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And also Keith, thanks for discovering the Hidden Rectangle 15 years ago. A must have in my toolbox!
immp |
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