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16-04-2023 VH

 
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peter urhegyi



Joined: 26 Oct 2020
Posts: 27

PostPosted: Sun Apr 16, 2023 9:47 pm    Post subject: 16-04-2023 VH Reply with quote

A sudoku as I like to see more in the daily sudokus. Only X,XY,XYZ wings, but this time a lot of them:
Code:

+-------+-------+-------+
| 6 . . | . . 2 | . . . |
| . 2 . | . . . | . 5 . |
| . . 3 | . 5 . | 8 . . |
+-------+-------+-------+
| . . . | . . 5 | . . 7 |
| 2 . . | . 8 3 | 4 . . |
| . . 8 | 1 7 . | . . . |
+-------+-------+-------+
| . . . | . . . | 7 . . |
| . 9 . | 6 . . | . . 2 |
| . . 1 | . . . | . 3 6 |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site
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dongrave



Joined: 06 Mar 2014
Posts: 560

PostPosted: Tue Apr 18, 2023 4:31 pm    Post subject: Reply with quote

Thanks for the puzzle Peter! After basics:

Code:
+----------------+---------------+---------------+
| 6     1458 459 |  348  19  2   |  39  7   1349 |
| 14789 2    479 |  3478 19  78  |  6   5   1349 |
| 1479  bf14 3   | e47   5   6   |  8   2  g149  |
+----------------+---------------+---------------+
| 149   b134 49  |  2    6   5   | a39  8   7    |
| 2      7   6   |  9    8   3   |  4   1   5    |
| 59     35  8   |  1    7   4   |  2   6   3-9  |
+----------------+---------------+---------------+
| 3      6   2   |  5    4   1   |  7   9   8    |
| 578    9   57  |  6    3   78  |  1   4   2    |
| 478   c48  1   | d78   2   9   |  5   3   6    |
+----------------+---------------+---------------+

I solved it using the following 6 VH moves but I'm not sure if they were all necessary. (I'll go back and check.) Note that you can apply the first 3 steps in any order.

Step 1. X Wing on 7's in rows 3 and 9 (-7r2c14,-7r8c1).
Step 2. X Wing on 9's in rows 3 and 6 (-9r1c9,-9r2c19,-9r4c1).
Step 3. XY Wing 78-4 at r3c4,r9c24 (-4r3c2).
Step 4. XY Wing 78-4 at r2c16,r3c4 (-4r2c4,-4r3c1).
Step 5. XYZ Wing 479 at r24c3,r3c1 (-9r1c3).
Step 6. XY Wing 48-5 at r1c3,r28c1 (-5r8c3).

Then I went back and solved it in one step by using the following chain: (9=3)r4c7-(3=1|4)r34c2-(4=8)r9c2-(8=7)r9c4-(7=4)r3c4-(4=1)r3c2-(14=9)r3c9 => r6c9 <> 9; stte.
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dongrave



Joined: 06 Mar 2014
Posts: 560

PostPosted: Fri Apr 21, 2023 9:20 pm    Post subject: Reply with quote

I hope that I'm not dissuading others from posting their solutions to the VH/VH+ puzzles on this 'Other puzzle' link. If anyone out there does not like me posting solutions so quickly, just let me know! I'd be glad to try to solve them but refrain from posting a solution (if I'm lucky enough to find one).
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TomC



Joined: 30 Oct 2020
Posts: 347
Location: Wales

PostPosted: Sat Apr 22, 2023 10:49 am    Post subject: Reply with quote

Nice puzzle Peter!

First time I did this I used lots of steps like dongrave (maybe more), I did use a <14> W wing in there as well

But on seeing dongrave's solution lead me to another one stepper below

Code:

+------------------+----------------+---------------+
| 6     d1458  459 |  348  19   2   |  39  7   1349 |
| 14789  2     479 |  3478 19  a78  |  6   5   1349 |
| 1479   14    3   |  47   5    6   |  8   2   149  |
+------------------+----------------+---------------+
| 149    134   49  |  2    6    5   |  39  8   7    |
| 2      7     6   |  9    8    3   |  4   1   5    |
| 59     35    8   |  1    7    4   |  2   6   39   |
+------------------+----------------+---------------+
| 3      6     2   |  5    4    1   |  7   9   8    |
| 578    9    c57  |  6    3   b78  |  1   4   2    |
| 478    48    1   |  78   2    9   |  5   3   6    |
+------------------+----------------+---------------+

Remove <8> from r2c6 to solve

If a=8, b=7, c=5, d=5 leads to no <8> in row 1


It's always nice to see different ways of solving, carry on dongrave!
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glesco



Joined: 12 May 2022
Posts: 35

PostPosted: Sat Apr 22, 2023 9:06 pm    Post subject: Reply with quote

Using my pen & pencil method, starting approximately where dongrave has the puzzle, I used the "3D Medusa" method. Starting with a base on Row 6, I eventually found a contradiction with 4s on column 2. That solved a lot with basic techniques to complete.
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immpy



Joined: 06 May 2017
Posts: 569

PostPosted: Tue Apr 25, 2023 5:55 pm    Post subject: Reply with quote

Great puzzle showcasing the VH solving techniques. Thanks peter.
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