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Sep 19 VH

 
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 941
Location: Rimini, Italy
PostPosted: Sun Sep 19, 2021 11:54 am    Post subject: Sep 19 VH Reply with quote
Hi everyone,

Code:

+--------------+-----------+---------------+
| 3789 3679 68 | 367 2  4  | 3569 1356 136 |
| 5    36   4  | 136 69 19 | 2    7    8   |
| 379  2    1  | 367 8  5  | 369  4    36  |
+--------------+-----------+---------------+
| 4    16   9  | 8   5  2  | 7    136  136 |
| 2    1567 68 | 4   3  67 | 56   1568 9   |
| 78   567  3  | 9   1  67 | 4    568  2   |
+--------------+-----------+---------------+
| 6    8    5  | 2   4  3  | 1    9    7   |
| 39   4    2  | 16  7  19 | 8    36   5   |
| 1    39   7  | 5   69 8  | 36   2    4   |
+--------------+-----------+---------------+

Play this puzzle online at the Daily Sudoku site

in one step AIC in r1c3
if r1c3 is 6 -6 in r12c2,r5c3
if r1c3 is 8 r5c8=8 r5c2=1 r4c2=6 and -6 in r12c2,r5c3

or in 2 steps
first
XY-Wing 3,6,9 in r2c25,r9c2 and -9 in r9c5

Code:

+-------------+----------+-------------+
| 789 367  68 | 367 2 4  | 569 135 136 |
| 5   36   4  | 36  9 1  | 2   7   8   |
| 79  2    1  | 367 8 5  | 69  4   36  |
+-------------+----------+-------------+
| 4   16   9  | 8   5 2  | 7   13  136 |
| 2   1567 68 | 4   3 67 | 56  158 9   |
| 78  567  3  | 9   1 67 | 4   58  2   |
+-------------+----------+-------------+
| 6   8    5  | 2   4 3  | 1   9   7   |
| 3   4    2  | 1   7 9  | 8   6   5   |
| 1   9    7  | 5   6 8  | 3   2   4   |
+-------------+----------+-------------+

Play this puzzle online at the Daily Sudoku site

second step
XY-Wing 5,6,8 in r5c37,r6c8 and -8 in r5c8,r6c1

Ciao Gianni
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TomC



Joined: 30 Oct 2020
Posts: 358
Location: Wales
PostPosted: Sun Sep 19, 2021 1:38 pm    Post subject: Reply with quote
I used two XY wings
first XY 678 -7 in r5c2 and r6c6
then the same second step as Gianni
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Mogulmeister



Joined: 03 May 2007
Posts: 1151
PostPosted: Sun Sep 19, 2021 3:00 pm    Post subject: Reply with quote
Looking at Gianni's AIC we can see that pincers for 6 are at r1c3 and r4c2 - one of these pincers must be 6.

Eureka as follows.

Even when we set r1c3 to "not 6" ie 8, the other pincer r4c2 is 6 removing r12c2,r5c3

8-6(r1c3)=(6-8)r5c3=(8-156)=1(r5c2)-(1=6)r4c2

Going the other way, if we set the other pincer r4c2 to "not 6" ie 1, then r1c3 is 6 also removing r12c2,r5c3

6=1(r4c2)-(r5c2)=(1-568)r5c8=(8-6)r5c3=(6-8)r1c3
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