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Oct 29 VH

 
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 868
Location: Rimini, Italy

PostPosted: Fri Oct 29, 2021 8:52 am    Post subject: Oct 29 VH Reply with quote

Hi everyone,

Code:

+----------+--------+-------------+
| 16  8 7  | 4 9 36 | 2   13 5    |
| 156 9 56 | 2 8 37 | 37  4  16   |
| 2   3 4  | 5 1 67 | 678 9  68   |
+----------+--------+-------------+
| 8   4 39 | 6 7 1  | 5   23 29   |
| 7   2 39 | 8 4 5  | 13  6  19   |
| 56  1 56 | 3 2 9  | 4   8  7    |
+----------+--------+-------------+
| 9   6 18 | 7 3 2  | 18  5  4    |
| 3   7 18 | 9 5 4  | 168 12 1268 |
| 4   5 2  | 1 6 8  | 9   7  3    |
+----------+--------+-------------+

Play this puzzle online at the Daily Sudoku site

Quote:
XY-Wing 1,2,3 in r48c8,r5c7 and -1 in r78c7
or
UR 5,6 in r26c13 and r2c1=1


Ciao Gianni
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Fri Oct 29, 2021 1:50 pm    Post subject: Reply with quote

Pincers on 1's in r1c8 and r5c9 give -1 in r2c9 so r2c9=6
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Oct 29, 2021 2:52 pm    Post subject: Reply with quote

R2C1 must be 1 because of the UR* at r26c13.

*Unique Rectangle.


Last edited by Mogulmeister on Fri Oct 29, 2021 3:09 pm; edited 1 time in total
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Oct 29, 2021 3:08 pm    Post subject: Reply with quote

TomC wrote:
Pincers on 1's in r1c8 and r5c9 give -1 in r2c9 so r2c9=6


Looks like a long backed chair !
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Fri Oct 29, 2021 3:22 pm    Post subject: Reply with quote

I saw it as a dog leg! (your chair would fall over)

Just noticed with the pincers, you could have r8c8=2 as otherwise it would force r2c9=1
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Oct 29, 2021 3:27 pm    Post subject: Reply with quote

TomC wrote:
I saw it as a dog leg! (your chair would fall over)


Right enough but I incorporated the single 6 to hold it up. Like those dodgy constellations in the night sky.
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sat Oct 30, 2021 12:18 am    Post subject: Reply with quote

Mogulmeister wrote:
R2C1 must be 1 because of the UR* at r26c13.

*Unique Rectangle.


OK already posted by Gianni. I couldn't do the right click reveal on my iphone while I was out - sorry for repeating.

So instead look at r5c9.

If it is 1 then obviously r5c7 two doors down, is going to = 3

But lets follow that 1 again but take a different chain route

(9=1)r5c9-r2c9=(1-3)r1c8=(3-7)r2c7-(3=1)r5c7 so r5c7 < > 3

So a contradiction when you put a 1 in r5c9 it can also put a 1 (not 3) in r5c7.

Clearly r5c9 < > 1
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Sat Oct 30, 2021 10:17 am    Post subject: Reply with quote

Nice contradiction

Another way to view this is to focus on r1c8 <13>

If either r5c7=3 or r5c9=1 you would get r1c8 containing both 1 and 3
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Mon Nov 01, 2021 10:26 am    Post subject: Reply with quote

Nice obverse!

Contradiction Recapitulation


We can see that the contradiction world can:

1)Put too many of the same numbers into a house
2)Remove a number totally from a house
3)Create a loop where the starting number is removed
4)Create a loop where a number is forced in even when removed at the start
5)Create multiple numbers in the same square location as the answer
6)Remove all numbers so the a square is vacant
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