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VH+ 100822

 
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immpy



Joined: 06 May 2017
Posts: 570

PostPosted: Sat Oct 08, 2022 9:07 pm    Post subject: VH+ 100822 Reply with quote

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 |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

cheers...immp
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glesco



Joined: 12 May 2022
Posts: 35

PostPosted: Sun Oct 09, 2022 8:42 pm    Post subject: Reply with quote

An xy-chain anchored at r5c1 & r4c8 eliminates 9 in r4c1
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dongrave



Joined: 06 Mar 2014
Posts: 563

PostPosted: Mon Oct 10, 2022 12:04 am    Post subject: Reply with quote

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

PostPosted: Mon Oct 10, 2022 12:34 am    Post subject: Reply with quote



    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: 563

PostPosted: Mon Oct 10, 2022 2:34 am    Post subject: Reply with quote

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: 349
Location: Wales

PostPosted: Mon Oct 10, 2022 7:26 am    Post subject: Reply with quote

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  |
+--------------------+-------------------+------------+

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: 35

PostPosted: Mon Oct 10, 2022 9:41 am    Post subject: Reply with quote

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: 563

PostPosted: Mon Oct 10, 2022 2:59 pm    Post subject: Reply with quote

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: 1110
Location: Dar es Salaam Tanzania

PostPosted: Mon Oct 10, 2022 6:58 pm    Post subject: Reply with quote

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: 570

PostPosted: Mon Oct 10, 2022 7:59 pm    Post subject: Reply with quote

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: 570

PostPosted: Mon Oct 10, 2022 8:03 pm    Post subject: Reply with quote

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: 1110
Location: Dar es Salaam Tanzania

PostPosted: Mon Oct 10, 2022 8:27 pm    Post subject: VH 100822 Reply with quote

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  |
+---------------------+--------------------+--------------+

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  |
+-------------------+----------------------+---------------+

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: 563

PostPosted: Mon Oct 10, 2022 8:52 pm    Post subject: Reply with quote

Very interesting puzzle! Thanks immp for posting it and thanks everyone for your input!
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glesco



Joined: 12 May 2022
Posts: 35

PostPosted: Tue Oct 11, 2022 10:45 pm    Post subject: Reply with quote

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: 563

PostPosted: Wed Oct 12, 2022 1:03 am    Post subject: Reply with quote

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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