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Jun 09 VH

 
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ZeroAssoluto



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

PostPosted: Thu Jun 09, 2022 10:12 am    Post subject: Jun 09 VH Reply with quote

Hi everyone,

Code:

+-----------+------------+----------------+
| 5 13  7   | 12 4    6  | 123  8     9   |
| 4 139 2   | 8  139  5  | 13   7     6   |
| 6 8   139 | 7  1239 23 | 4    1235  135 |
+-----------+------------+----------------+
| 9 2   18  | 36 5    4  | 1368 136   7   |
| 3 6   58  | 12 12   7  | 58   9     4   |
| 7 145 145 | 36 8    9  | 1356 1356  2   |
+-----------+------------+----------------+
| 2 34  6   | 5  7    1  | 9    34    8   |
| 8 359 359 | 4  236  23 | 7    12356 135 |
| 1 7   345 | 9  236  8  | 2356 23456 35  |
+-----------+------------+----------------+

Play this puzzle online at the Daily Sudoku site

Quote:
In one step
Swordfish with number 3 in r389c369 and -3 in r3c58,r8c258,r9c578
or
XY-Wing 1,2,3 in r1c24,r3c6 and -3 in r3c3
and L.C. in c2


Ciao Gianni
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS

PostPosted: Thu Jun 09, 2022 11:33 am    Post subject: Jun06VH Reply with quote

If basics are used first, the 123xywing should do it.

Early Earl
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ZeroAssoluto



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

PostPosted: Fri Jun 10, 2022 9:23 am    Post subject: Reply with quote

If you don't delete number 3 from r3c3 (with the XY-Wing) you don't have the LC in column 2 with number 3.

Ciao Gianni
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Fri Jun 10, 2022 11:44 am    Post subject: Reply with quote

Or you could say a=4 to solve
Code:

+------------+---------------+----------------+
| 5 b13  7   | c12  4     6  | 123  8     9   |
| 4  139 2   |   8  139   5  | 13   7     6   |
| 6  8   139 |   7  1239 d23 | 4    1235  135 |
+------------+---------------+----------------+
| 9  2   18  |  36  5     4  | 1368 136   7   |
| 3  6   58  |  12  12    7  | 58   9     4   |
| 7  145 145 |  36  8     9  | 1356 1356  2   |
+------------+---------------+----------------+
| 2 a34  6   |  5   7     1  | 9    34    8   |
| 8  359 359 |  4   236   23 | 7    12356 135 |
| 1  7   345 |  9   236   8  | 2356 23456 35  |
+------------+---------------+----------------+

If a=3, b=1, c=2, d=3 leads to no <3> in box 1
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sat Jun 11, 2022 2:39 pm    Post subject: Reply with quote

Picking up a little on all these themes there is another structure that gets us to the same conclusion as Tom’s contradiction.

Using Tom’s grid, incorporating a, is an ANP <139> at r12c2.

If ANP is true then the <13> pair eliminates the <3> at a making a = 4

If ANP is false then r2c2 = 9 which creates an XY wing with c and d.
This makes b = 3 and this makes a = 4.


Last edited by Mogulmeister on Tue Jun 14, 2022 3:22 pm; edited 1 time in total
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sat Jun 11, 2022 6:47 pm    Post subject: Reply with quote

ZeroAssoluto wrote:
If you don't delete number 3 from r3c3 (with the XY-Wing) you don't have the LC in column 2 with number 3.

Ciao Gianni


….but Earl’s <123> XY at bcd is sufficient to remove the 3 from r3c3. This means the 3’s in col 2 mean a = 4
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Sat Jun 11, 2022 8:20 pm    Post subject: Reply with quote

I think it's always good to look at solutions in different ways.

The ANP by Mogulmeister could also be looked at as:

In box 1 it doesn't matter where you put <9> "a" is always <4>
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sat Jun 11, 2022 8:38 pm    Post subject: Reply with quote

That’s right. Thanks Tom. Should have made that explicit. Whether ANP true or false or wherever the 9, the answer is that “a” is always 4
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ZeroAssoluto



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

PostPosted: Sun Jun 12, 2022 10:08 am    Post subject: Reply with quote

Mogulmeister wrote:
ZeroAssoluto wrote:
If you don't delete number 3 from r3c3 (with the XY-Wing) you don't have the LC in column 2 with number 3.

Ciao Gianni


….but Earl’s <123> XY at bcd is sufficient to remove the 3 from r3c3. This means the 3’s in col 2 mean a = 4


I said first XY-Wing then LC

Earl said first basic

I don't see basic as first step

Ciao Gianni
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sun Jun 12, 2022 10:35 am    Post subject: Reply with quote

I think the basic must come after the <123> ?
Once you have removed the 3 from r3c3 it is just basics.
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ZeroAssoluto



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

PostPosted: Sun Jun 12, 2022 12:25 pm    Post subject: Reply with quote

When I talk about basics I am talking about the simplest techniques (LC, Pairs, Triples).

In this case I think LC should come after XY-Wing, not before, not as the first step.
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sun Jun 12, 2022 2:13 pm    Post subject: Reply with quote

Yes that is also what I was saying. I think Earl may have meant to say xy wing and then “btte.” I think we note basics but don’t regard them as a step as the eliminations are implicit.
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