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immpy
Joined: 06 May 2017
Posts: 571
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 Posted: Sat Oct 08, 2022 9:07 pm Post subject: VH+ 100822 |
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Hello all, enjoy the puzzle.
| Code: |
+-------+-------+-------+
| 6 5 . | 3 . 4 | 7 . . |
| 3 . . | . 5 . | 2 . . |
| . . 9 | . 7 . | . 5 6 |
+-------+-------+-------+
| . . 5 | . . 2 | . . 1 |
| . . . | . . . | 8 7 . |
| . 3 . | 8 . . | . . 5 |
+-------+-------+-------+
| . . . | . . 5 | 9 . . |
| . 6 . | 9 . . | . . 4 |
| 4 . . | . . . | . 8 7 |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
cheers...immp |
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glesco
Joined: 12 May 2022
Posts: 36
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| Posted: Sun Oct 09, 2022 8:42 pm Post subject: |
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| An xy-chain anchored at r5c1 & r4c8 eliminates 9 in r4c1 |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Mon Oct 10, 2022 12:04 am Post subject: |
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Could you be more specific glesco? I don't see the xy chain that you're describing. I'll go enter the grid that I ended up with after basics and then I'll update this post to include it.
(Update:) Here's the grid that I ended up with after basics. Let me know if I missed anything!
| Code: |
+-----------------+-----------------+-----------+
| 6 5 28 | 3 289 4 | 7 1 89 |
| 3 178 178 | 16 5 1689 | 2 4 89 |
| 128 4 9 | 12 7 18 | 3 5 6 |
+-----------------+-----------------+-----------+
| 789 78 5 | 47 3469 2 | 46 39 1 |
| 129 12 46 | 5 13469 1369 | 8 7 23 |
| 1279 3 46 | 8 19 179 | 46 29 5 |
+-----------------+-----------------+-----------+
| 1278 1278 12378 | 47 12348 5 | 9 6 23 |
| 5 6 2378 | 9 238 378 | 1 23 4 |
| 4 9 123 | 126 1236 136 | 5 8 7 |
+-----------------+-----------------+-----------+
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Pat
Joined: 23 Feb 2010
Posts: 207
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| Posted: Mon Oct 10, 2022 12:34 am Post subject: |
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if r4c1=9 then
r4c8=3
r5c9=2
r5c2=1
r5c1 nothing left
what do we call this? |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Mon Oct 10, 2022 2:34 am Post subject: |
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| Ah! Good eye Pat! You could simply represent it as a chain that leads to a contradiction: 9r4c1 - (9=3)r4c8 - (3=2)r5c9 - (2=1)r5c2 - (12=9)r5c1 contradiction => r4c1 <> 9 BUT! - I don't think that it solves the puzzle! |
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TomC
Joined: 30 Oct 2020
Posts: 358
Location: Wales
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| Posted: Mon Oct 10, 2022 7:26 am Post subject: |
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My solution was to remove <2> from r89c3 to solve
| Code: |
+--------------------+-------------------+------------+
| 6 5 .28 | 3 .289 4 | 7 1 89 |
| 3 178 178 | 16 5 1689 | 2 4 89 |
| 128 4 9 | 12 7 18 | 3 5 6 |
+--------------------+-------------------+------------+
| e789 e78 5 | f47 3469 2 | 46 d39 1 |
| 129 12 46 | 5 13469 1369 | 8 7 23 |
| 1279 3 46 | 8 19 179 | 46 29 5 |
+--------------------+-------------------+------------+
| 1278 1278 12378 | g47 .12348 5 | 9 6 23 |
| 5 6 b2378 | 9 .238 378 | 1 c23 4 |
| 4 9 a123 | 126 1236 136 | 5 8 7 |
+--------------------+-------------------+------------+
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Play this puzzle online at the Daily Sudoku site
If a=2 this would lead to no <2> in row 1 or no <2> in box 8
If b=2, c=3, d=9, e=<78>, f=4, g=7 leads to no <7> in box 7 |
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glesco
Joined: 12 May 2022
Posts: 36
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| Posted: Mon Oct 10, 2022 9:41 am Post subject: |
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dongrave,
I used an x-wing on columns 2&9 to eliminate 2s in r5c1 & other cells. Then (9=1)r5c1 - (1=2)r5c2 - (2=3)r5c9 - (3=9)r4c8 --> -9r4c1. |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Mon Oct 10, 2022 2:59 pm Post subject: |
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| glesco wrote: | dongrave,
I used an x-wing on columns 2&9 to eliminate 2s in r5c1 & other cells. Then (9=1)r5c1 - (1=2)r5c2 - (2=3)r5c9 - (3=9)r4c8 --> -9r4c1. |
Oh, I see! I was unable to solve the puzzle with just basics after making those moves though. I think you might need another advanced move? Or maybe I'm missing something? |
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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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| Posted: Mon Oct 10, 2022 6:58 pm Post subject: |
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| Pat wrote: |
if r4c1=9 then
r4c8=3
r5c9=2
r5c2=1
r5c1 nothing left
what do we call this? |
It is called a cell forcing chain or a kraken cell if you put it the other way round i.e you start with the cell:
1r5c1 - (1=23)r5c29 - (3=9)r4c8 - (9)r4c1
2r5c1 - (2=3)r5c8 - (3=9)r4c8 - (9)r4c1
9r5c1 - (9)r4c1 => - 9r4c1
That is whatever the solution in r5c1, 9 is eliminated in r4c1. However it does not solve the puzzle. |
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immpy
Joined: 06 May 2017
Posts: 571
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| Posted: Mon Oct 10, 2022 7:59 pm Post subject: |
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| I followed the path of the X-Wing on 2 to begin eliminations as well. Then identified an XY-Chain: 9 9- r4c8 -3- r5c9 -2- r5c1 -9=> r4c1<>9. |
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immpy
Joined: 06 May 2017
Posts: 571
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| Posted: Mon Oct 10, 2022 8:03 pm Post subject: |
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| After a good rinse with basics, the Skyscraper: 2 in r1c3,r3c4 (connected by r9c34)=>r1c5,r3c1<>2. |
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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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| Posted: Mon Oct 10, 2022 8:27 pm Post subject: VH 100822 |
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Opted for three steps | Code: |
+---------------------+--------------------+--------------+
| 6 5 28 | 3 289 4 | 7 1 89 |
| 3 178 178 | 16 5 1689 | 2 4 89 |
| 128 4 9 | 12 7 18 | 3 5 6 |
+---------------------+--------------------+--------------+
|d789 d78 5 | 47 3469 2 | 46 c39 1 |
| 129 12 46 | 5 13469 1369 | 8 7 23 |
| 129-7 3 46 | 8 a19 a179 | 46 b29 5 |
+---------------------+--------------------+--------------+
| 1278 1278 12378 | 47 12348 5 | 9 6 23 |
| 5 6 2378 | 9 238 378 | 1 23 4 |
| 4 9 123 | 126 1236 136 | 5 8 7 |
+---------------------+--------------------+--------------+
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Step 1: (7=1|9)r6c56 - (9)r6c8 = r4c8 - (9=7|8)r4c12 => - 7r6c1
| Code: |
+-------------------+----------------------+---------------+
| 6 5 c28 | 3 d289 4 | 7 1 89 |
| 3 7 18 | 16 5 1689 | 2 4 89 |
| 128 4 9 | 12 7 18 | 3 5 6 |
+-------------------+----------------------+---------------+
| 7 8 5 | 4 39 2 | 6 39 1 |
| 129 12 4 | 5 1369 1369 | 8 7 23 |
| 129 3 6 | 8 19 179 | 4 29 5 |
+-------------------+----------------------+---------------+
| 18-2 a12 138-2| 7 12348 5 | 9 6 3-2|
| 5 6 7 | 9 e238 38 | 1 f23 4 |
| 4 9 b123 | 126 1236 136 | 5 8 7 |
+-------------------+----------------------+---------------+
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Step 2: X-Wing on (2)r57c29 => - 2r7c13
Step 3: (2)r7c2 = r9c3 - r1c3 = r1c5 - r8c5 = (2)r8c8 => - 2r7c9;stte |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Mon Oct 10, 2022 8:52 pm Post subject: |
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| Very interesting puzzle! Thanks immp for posting it and thanks everyone for your input! |
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glesco
Joined: 12 May 2022
Posts: 36
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| Posted: Tue Oct 11, 2022 10:45 pm Post subject: |
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dongrave,
Unfortunately I have thrown away my paper & pen sheet on this puzzle. Recalling best I can from reviewing your grid, I suspect I used a skyscraper on 2s from columns 3&4 which gives a bunch of eliminations. Hope this clarifies things! |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Wed Oct 12, 2022 1:03 am Post subject: |
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| glesco wrote: | dongrave,
Unfortunately I have thrown away my paper & pen sheet on this puzzle. Recalling best I can from reviewing your grid, I suspect I used a skyscraper on 2s from columns 3&4 which gives a bunch of eliminations. Hope this clarifies things! |
Oh! Thanks glesco! I always throw mine away when I'm done too! |
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