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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Sat Feb 09, 2008 11:08 pm Post subject: Feb 10 vh |
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A little diversity can't hurt:
x-wing (removed 1)
xy-wing (removed 5) and
xyz-wing (removed 9)
All the wings having an x in their name...
Feb 10 - "x-day"? Shall I call the ex and send greetingss? Nah ... |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Sun Feb 10, 2008 12:09 am Post subject: |
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| Quote: | | Shall I call the ex and send greetingss? |
Better not nataraj, because my ex is useless 
There is a useless [45-145-14] xyz-wing@ that takes out <9> in R4C8, after that just singles to the end.
The common digit <4> must appear in one of those three cells. These three possibile cells for placing <4> results in two pincer cells for digit <9>, either
R4C3=9(a) or R7C8=9(b), which eliminates <9> in R4C8.
a. R2C17=|4| => R2C3=|1| => R5C3=|6| => R4C3=|9|
b. R3C9={4} => R7C9={1} => R7C8={9}
| Code: | +--------------------------+--------------------------+--------------------------+
| 249 8 3 | 5 1 49 | 246 26 7 |
||4|5@ 6 |1|4 | 2 3 7 | 1|4|5@ 8 9 |
| 25 149 7 | 8 6 49 | 235 235 @1{4} |
+--------------------------+--------------------------+--------------------------+
| 8 3 a 6|9| | 4 5 1 | 7 26-[9] 26 |
| 7 5 1|6| | 3 9 2 | 16 4 8 |
| 49 149 2 | 7 8 6 | 159 159 3 |
+--------------------------+--------------------------+--------------------------+
| 3 7 8 | 6 2 5 | 149 b 1{9} {1}4 |
| 1 24 45 | 9 7 8 | 236 236 256 |
| 6 29 59 | 1 4 3 | 8 7 25 |
+--------------------------+--------------------------+--------------------------+ |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Feb 10, 2008 5:26 am Post subject: |
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you can put me down for:
x-wing on 1,
{4,5,9} xy-wing, pincers in r2c1, r6c7,
I made the basic eliminations after the xy-wing and...
I have a question at this point in the grid:
are the # marked squares a nice loop, or a unique loop??
r1c6 {4,9)
r1c1 {4,9}
r6c1 {4,9}
r6c2 {1,4,9}
r3c2 {1,4,9}
r3c6 {4,9}
| Code: | |---c1--|---c2--|---c3--||---c4--|---c5--|---c6--||---c7--|---c8--|---c9--
-----------------------------------------------------------------------------
r1 | #49 | 8 | 3 || 5 | 1 | #49 || 26 | 26 | 7
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r2 | 5 | 6 | 14 || 2 | 3 | 7 || 14 | 8 | 9
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r3 | 2 | #149 | 7 || 8 | 6 | #49 || 35 | 35 | 14
===========================||=======================||=======================
r4 | 8 | 3 | 69 || 4 | 5 | 1 || 7 | 269 | 26
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r5 | 7 | 5 | 16 || 3 | 9 | 2 || 16 | 4 | 8
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r6 | #49 | #149 | 2 || 7 | 8 | 6 || 59 | 159 | 3
===========================||=======================||=======================
r7 | 3 | 7 | 8 || 6 | 2 | 5 || 49 | 19 | 14
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r8 | 1 | 24 | 45 || 9 | 7 | 8 || 236 | 236 | 256
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r9 | 6 | 29 | 59 || 1 | 4 | 3 || 8 | 7 | 25
............................................................................. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Sun Feb 10, 2008 1:19 pm Post subject: |
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| The 49's from a unique loop, but its useless, because we also know without it, that one of r36c2 must be 1. |
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George Woods
Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK
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| Posted: Sun Feb 10, 2008 1:37 pm Post subject: Another Maverik one |
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Every time I solve a VH via a Maverik solution, I repeat the process trying to find an "authorised solution".
The strange thing about this one is that after the Xwing I didn't need the XY wing that I used first time en route to the maverik process.
So in this grid after the X wing where I have not eliminated all the other more subtle candidates.
| Code: |
+------------------+--------+-----------------+
| 2459 8 3 | 5 1 49 | 2456 256 7 |
| 45 6 145 | 2 3 7 | 145 8 9 |
| 24579 1249 14579 | 8 6 49 | 12345 1235 1245 |
+------------------+--------+-----------------+
| 8 3 69 | 4 5 1 | 7 269 26 |
| 7 5 167 | 3 9 2 | 16 4 8 |
| 49 149 2 | 7 8 6 | 59 159 3 |
+------------------+--------+-----------------+
| 3 7 8 | 6 2 5 | 149 19 14 |
| 1 24 45 | 9 7 8 | 23456 2356 2456 |
| 6 29 59 | 1 4 3 | 8 7 25 |
+------------------+--------+-----------------+
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[url=http://www.dailysudoku.com/sudoku/play.shtml?p=2459:8:3:5:1:49:2456:256:7:45:6:145:2:3:7:145:8:9:24579:1249:14579:8:6:49:12345:1235:1245:8:3:69:4:5:1:7:269:26:7:5:167:3:9:2:16:4:8:49:149:2:7:8:6: 59:159:3:3:7:8:6:2:5:149:19:14:1:24:45:9:7:8:23456:2356:2456:6:29:59:1:4:3:8:7:25:]Play this puzzle online[/url] at the Daily Sudoku site
I looked at the effect of r6c8 being 1 - If so it kills all the 9s in col 7 (via the 49 pair in box4 or the 19 in box 9) so r5c7 is 1 and that solves it.
THE POINT OF THIS IS THAT ONCE SEEN THIS IS SO OBVIOUS, BUT I COULDN'T FORCE IT INTO ONE OF THE STANDARD FORMS- CAN ANYONE HELP? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Feb 10, 2008 4:41 pm Post subject: |
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I must've missed something. At any rate, after a couple of ERs, an X-Wing, W-Wing and two XY-Wings, I found myself at this position.
| Code: | +------------+--------+--------------------+
| 249 8 3 | 5 1 49 | 246 26 7 |
| 5 6 14 | 2 3 7 | 14 8 9 |
| 249 149 7 | 8 6 49 | 2345 235 1245 |
+------------+--------+--------------------+
| 8 3 69 | 4 5 1 | 7 26-9APE 26 |
| 7 5 16 | 3 9 2 | 16 4 8 |
| 49 149 2 | 7 8 6 | 59 159APE 3 |
+------------+--------+--------------------+
| 3 7 8 | 6 2 5 | 49 19 14 |
| 1 24 45 | 9 7 8 | 2356 2356 256 |
| 6 29 59 | 1 4 3 | 8 7 25 |
+------------+--------+--------------------+ |
There is a rare (for me) Aligned Pair Exclusion, so marked in r46c8. The 9 is gone from r4c8 because 99 is invalid, 95 is excluded because of r6c7 and 91 because of r7c8. The puzzle is solved after removal of the 9. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Feb 10, 2008 5:55 pm Post subject: |
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| Quote: | | The 49's from a unique loop, but its useless, because we also know without it, that one of r36c2 must be 1. |
Ravel,
thankyou,
so to make an elimination with that configuration, there would need to be another 1 in col 2. very cool.  |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Sun Feb 10, 2008 7:38 pm Post subject: feb 10 VH |
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I had to use two xy-chains to eliminate the 9 in R6C1 and R6C7.
Not very sophisticated, but it worked.
Will a medusa solve it?
A VH worthy of the rating.
Earl |
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TexCat
Joined: 07 Jul 2006
Posts: 32
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| Posted: Sun Feb 10, 2008 8:12 pm Post subject: |
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I am stuck at this point, and can't manage to see any xyz wing. Can anyone help with my next step?
| Code: |
+-----------+--------+-------------+
| 49 8 3 | 5 1 49 | 26 26 7 |
| 5 6 14 | 2 3 7 | 14 8 9 |
| 2 149 7 | 8 6 49 | 35 35 14 |
+-----------+--------+-------------+
| 8 3 69 | 4 5 1 | 7 269 26 |
| 7 5 16 | 3 9 2 | 16 4 8 |
| 49 149 2 | 7 8 6 | 59 159 3 |
+-----------+--------+-------------+
| 3 7 8 | 6 2 5 | 49 19 14 |
| 1 24 45 | 9 7 8 | 236 236 256 |
| 6 29 59 | 1 4 3 | 8 7 25 |
+-----------+--------+-------------+
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Play this puzzle online at the Daily Sudoku site
Edit: Marty, after posting this, I read up on your APE technique and now see how it works. Thanks. |
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sdq_pete
Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL
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| Posted: Sun Feb 10, 2008 9:41 pm Post subject: |
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I reached this position too. An XYZ wing on 159 with pivot at R6C8 eliminates 9 at R4C8 and finishes it off. Phew!
Peter |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Feb 10, 2008 10:06 pm Post subject: |
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| Quote: | | Edit: Marty, after posting this, I read up on your APE technique and now see how it works. Thanks. |
And, of course, while doing the APE I never saw the wing, which the APE should have alerted me to. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Sun Feb 10, 2008 10:20 pm Post subject: |
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George,
Your <1> elimination is an AIC. I'll give the Eureka notation in a moment. But first...
Appropriately for you (since you're the "W" in W-Wing), your AIC is just a W-Wing variant. A {19} W-Wing with an external <9> strong link can be considered as the reduction of two ALSs: in this case, the two {19} bivalue ALSs.
In the case above, you have a {19} ALS plus a {149} ALS (in r6c12) which the external strongly-linked <9> (in c7) would reduce to a {14} "pair." (This "pair" would actually be a fixed <1> and a fixed <4>; but that doesn't matter.) The effect is exactly the same as a W-Wing. Think of it as a remote ALS pair where the external strong link activates the shared exclusive digit and then the shared common digit performs the elimination.
Now, for the Eureka moment...
First, let's pretend that r6c2 is a {19} bivalue and it is a conventional W-Wing. The Eureka would be:
(1)r6c8-(1=9)r6c2-(9=9)r67c7-(9=1)r7c8-(1)r6c8; r6c8<>1
Now, let's take the actual case above:
(1)r6c8-({14}=9})r6c12-(9=9)r67c7-(9=1)r7c8-(1)r6c8; r6c8<>1
Perhaps the Eureka notation makes the W-Wing-related structure clear... or vice-versa!
Note: That {149} ALS could also have been written "(1={49})r6c12". Either way is fine. |
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George Woods
Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK
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| Posted: Sun Feb 10, 2008 10:57 pm Post subject: The AIC explanation |
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| Thanks Asselus for the interpretation - All I can say other than this is Wow! - the formal explanation is certainly more difficult (for me) than the original explanation. However I don't suppose I should be surprised since I often find a very convoluted deduction that such and such a square is 4 , only to find a simple scan of the column (or row) explains the deduction so much more simply! |
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