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VH++

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ravel

Joined: 21 Apr 2006
Posts: 536

Posted: Mon Mar 17, 2008 6:45 pm Post subject: VH++

I needed some "transports" from patterns like w- or (half) M-wings for this one.

Code:

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

>>> play online

Victor

Joined: 29 Sep 2005
Posts: 207
Location: NI

Posted: Mon Mar 17, 2008 8:29 pm Post subject:

Code:

+--------------+-------------+--------------+
| 125 6 7 | 9 8 14 | 1245 1245 23 |
| 8 19 12 | 124 5 3 | 1247 79 6 |
| 3 159 4 | 12 6 7 | 125 8 29 |
+--------------+-------------+--------------+
| 6 4 13 | 5 23 8 | 127 79 29 |
| 7 2 9 | 146 14 146 | 8 3 5 |
| 15 135 8 | 7 23 9 | 6 12 4 |
+--------------+-------------+--------------+
| 9 8 26 | 46 7 456 | 3 245 1 |
| 124 13 1236 | 8 9 1456 | 245 245 7 |
| 14 7 5 | 3 14 2 | 9 6 8 |
+--------------+-------------+--------------+

Play this puzzle online
An XY-chain jumped out at me: 1r2c2 = 1r6c8, which exposes an XY-wing, which solves the puzzle.
Kind of the reverse of a recent puzzle posted by Earl. I'm looking forward to the sophisticated method!

storm_norm

Joined: 18 Oct 2007
Posts: 1741

Posted: Mon Mar 17, 2008 8:46 pm Post subject:

Victor wrote:

Code:

victor,
I believe the xy-chain is a good first move after basics. it leads to an xy-wing which finishes it off.

ravel

Joined: 21 Apr 2006
Posts: 536

Posted: Tue Mar 18, 2008 4:09 pm Post subject:

Victor wrote:

I'm looking forward to the sophisticated method!

This time my preference for remote pairs made me blind for the xy-chain, which is not hard to spot and more effective.

Code:

*---------------------------------------------------*
| 125 6 7 | 9 8 14 | 1245 145 3 |
| 8 -19 #12 | 124 5 3 | 1247 79 6 |
| 3 159 4 | 12 6 7 | 125 8 29 |
|-----------------+----------------+----------------|
| 6 4 &*13 | 5 23 8 |*127 79 29 |
| 7 2 9 | 146 14 146 | 8 3 5 |
| 15 135 8 | 7 23 9 | 6 #12 4 |
|-----------------+----------------+----------------|
| 9 8 *26 | 46 7 456 | 3 *245 1 |
| 124 &13 -1-236 | 8 9 1456 | 245 245 7 |
| 14 7 5 | 3 14 2 | 9 6 8 |
*---------------------------------------------------*

I looked at the 12-pairs # in r2c3 and r6c8:
Its a w-wing with the both a strong link for 2 in row 7 and for 1 in row 4:
So one of the pairs must be 1 and the other 2.

1 and 2 can be transported from r6c8 over the strong links:
r6c8=1 => r4c3=1 ==> r8c3<>1 and
r6c8=2 => r7c3=2 ==> r8c3<>2.

But these are very weak eliminations. They only revealed a half M-wing 13 :
r8c2=3 => r6c2<>3 => r4c3=3.
With the eliminated 1 in r8c3 there is a strong link for 1 from r4c3 to r2c3 and we have
r8c2=1 or r3c2=1 ==> r2c2<>1

Victor

Joined: 29 Sep 2005
Posts: 207
Location: NI

Posted: Tue Mar 18, 2008 4:26 pm Post subject:

I asked for the the sophisticated method: certainly got it! Smart stuff as ever. I guess that, if I'd looked hard, I'd have seen that the 12s are conjugate, but I doubt if I'd have been able to make much further progress.

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