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Jan 22 VH

 
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 685
Location: Rimini, Italy

PostPosted: Sat Jan 22, 2022 10:21 am    Post subject: Jan 22 VH Reply with quote

Hi everyone,

Code:

+--------------+--------------+---------------+
| 5  24   234  | 7  134   12  | 9   8    6    |
| 79 2478 6    | 39 34589 258 | 357 2357 1    |
| 1  278  2389 | 6  3589  258 | 4   2357 25   |
+--------------+--------------+---------------+
| 79 2457 2459 | 39 3589  6   | 358 1    2458 |
| 8  1    25   | 4  35    7   | 6   235  9    |
| 6  3    459  | 2  1589  158 | 578 57   458  |
+--------------+--------------+---------------+
| 4  58   7    | 58 2     9   | 1   6    3    |
| 3  6    58   | 1  7     4   | 2   9    58   |
| 2  9    1    | 58 6     3   | 58  4    7    |
+--------------+--------------+---------------+

Play this puzzle online at the Daily Sudoku site

first step
AIC in r4c4
r4c4=9 and -9 in r4c13,r6c5
r4c4=3 r5c8=3 r4c9=2 r3c9=5 r8c9=8 r3c3=8 r3c5=9 r6c3=9 and -9 in r4c13.r6c5

Code:

+----------+------------+-------------+
| 5 24  3  | 7  14  12  | 9   8   6   |
| 9 248 6  | 3  458 258 | 57  257 1   |
| 1 7   28 | 6  9   258 | 4   3   25  |
+----------+------------+-------------+
| 7 25  4  | 9  58  6   | 3   1   258 |
| 8 1   25 | 4  3   7   | 6   25  9   |
| 6 3   9  | 2  158 158 | 578 57  4   |
+----------+------------+-------------+
| 4 58  7  | 58 2   9   | 1   6   3   |
| 3 6   58 | 1  7   4   | 2   9   58  |
| 2 9   1  | 58 6   3   | 58  4   7   |
+----------+------------+-------------+

Play this puzzle online at the Daily Sudoku site

second step
XY-Wing 2,5,8 in r3c39,r8c3 and -5 in r8c9

Ciao Gianni
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dongrave



Joined: 06 Mar 2014
Posts: 476

PostPosted: Sun Jan 23, 2022 1:26 pm    Post subject: Reply with quote

Using just standard VH moves I think you have to use the X-Wing on 9's in cols 1 and 4, the X-Wing on 3's in cols 4 and 7, a 578 XYZ-Wing with pivot at r6c7, and then a 58-3 XY-Wing with pivot at r4c5. After applying the X-Wing on 3's I also saw a 257 XYZ-Wing with pivot at r2c8 but it doesn't look like that was necessary.
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TomC



Joined: 30 Oct 2020
Posts: 227
Location: Wales

PostPosted: Sun Jan 23, 2022 1:46 pm    Post subject: Reply with quote

An alternative second step to Gianni's post

<25> W wing in r3c9 and r5c3 gives -2 in r3c3
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Mogulmeister



Joined: 03 May 2007
Posts: 1136

PostPosted: Sun Jan 23, 2022 6:17 pm    Post subject: Reply with quote

Another second step using Gianniís grid is the <248> ANP in r12c2.

If ANP is true then r4c2 = 5 r5c3 <> 5 r8c3 = 5 and r8c9 < > 5
If ANP is false then r2c2 = 8 r3c3 = 2 r3c9 = 5 and r8c9 < > 5
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Mogulmeister



Joined: 03 May 2007
Posts: 1136

PostPosted: Mon Jan 24, 2022 7:19 am    Post subject: Reply with quote

Don,

Given the variable nature of the grading algorithm, what grade do you think this one was at ?
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peter urhegyi



Joined: 26 Oct 2020
Posts: 15

PostPosted: Mon Jan 24, 2022 9:09 am    Post subject: 5 step daily sudoku 22-01-2022 Reply with quote

Dongrave found 4 of the 5 steps:
1)x-wing on 9's in cols 1&4
2)x-wing on 3's in cols 4&7
3)xyz-wing 578 with pivot at R6C7 (R4C7!=5)
4)xy-wing 58-3 with pivot at R4C5 (R4C4!=3 and R5C8!=3)
I needed one more step:
5a)xy-wing 28-5 with pivot at R3C3 (R8C9!=5 )
or
5b)xy-wing 25-8 with pivot at R3C9 (R8C3!=8 )


Last edited by peter urhegyi on Mon Jan 24, 2022 9:31 am; edited 4 times in total
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Mogulmeister



Joined: 03 May 2007
Posts: 1136

PostPosted: Mon Jan 24, 2022 9:23 am    Post subject: Reply with quote

Thanks Peter.
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TomC



Joined: 30 Oct 2020
Posts: 227
Location: Wales

PostPosted: Mon Jan 24, 2022 10:37 am    Post subject: Reply with quote

Another second step using Gianniís grid is -8 in r4c9 as this is needed to avoid the <57> UR in r26c78

This has certainly been the trickiest VH for a while!
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Mogulmeister



Joined: 03 May 2007
Posts: 1136

PostPosted: Mon Jan 24, 2022 11:21 am    Post subject: Reply with quote

I don't know for sure, but if that had appeared in The Telegraph it might well have been deemed a diabolical ?
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Mogulmeister



Joined: 03 May 2007
Posts: 1136

PostPosted: Mon Jan 24, 2022 11:38 am    Post subject: Reply with quote

TomC wrote:
Another second step using Gianniís grid is -8 in r4c9 as this is needed to avoid the <57> UR in r26c78

This has certainly been the trickiest VH for a while!


Good spot Tom
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dongrave



Joined: 06 Mar 2014
Posts: 476

PostPosted: Mon Jan 24, 2022 2:32 pm    Post subject: Reply with quote

Thanks for pointing that out Peter! I must have made an error somewhere along the way! I had a tough time with that one!
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