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ravel
Joined: 21 Apr 2006
Posts: 536
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 Posted: Thu Apr 24, 2008 4:44 pm Post subject: Another VH+ by gsf |
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| Code: | +-------+-------+-------+
| . 8 6 | . . . | . . 1 |
| 5 . 7 | . . . | . . . |
| 2 3 . | 5 . . | . . . |
+-------+-------+-------+
| . . 5 | . 3 1 | . . . |
| . . . | 9 . 8 | . . . |
| . . . | 4 2 . | 9 . . |
+-------+-------+-------+
| . . . | . . 6 | . 9 3 |
| . . . | . . . | 8 . 7 |
| 4 . . | . . . | 6 2 . |
+-------+-------+-------+ gsf
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>>> play online |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Apr 24, 2008 8:15 pm Post subject: |
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3 different advanced techniques:
UR type 1: 68 => r2c5=1. (This one appeared fairly early in the game, after the NP 68 in col 8 )
w-wing: 47-47 via 14-14 in box 9 => r4c8=7
kite: 4 r8-box 9-col 8 => r1c5=7
great puzzle! |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Thu Apr 24, 2008 11:33 pm Post subject: |
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nataraj, go back to your w-wing grid... i see two w-wings on {4,7}
one connected via the 1,4 cells in box 9 ( as you pointed out ) and another w-wing via the {4,7} in r1c5 and r3c7 connected to the strong links on 4 in r7c5 and r7c7. you might have seen this already, just interesting that there are two w-wings present on the same pair of candidates just in different cells.
| Code: | 9 8 6 | 37 47 2347 | 23457 3457 1
5 4 7 | 8 1 239 | 23 6 29
2 3 1 | 5 6 479 | 47 8 49
------------------------------------------------------------------
8 9 5 | 6 3 1 | 247 47 24
17 2 4 | 9 57 8 | 135 135 6
6 17 3 | 4 2 57 | 9 15 8
------------------------------------------------------------------
17 5 28 | 127 48 6 | 14 9 3
3 6 29 | 12 459 45 | 8 14 7
4 17 89 | 137 89 37 | 6 2 5 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Apr 24, 2008 11:59 pm Post subject: |
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| I needed a few more steps. But, as Norm pointed out, there are two W-Wings on 47 and I used them both. For me, the 68 UR was a Type 4, not Type 1. I also used an XYZ-Wing and a kite on 7, but it was coloring on 4 which finished it off. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Apr 25, 2008 12:34 am Post subject: |
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After the Type 1 UR on {68}, I found a xy-wing on {145} with the pivot at r8c8 and pincers at r8c6 & r6c8 that deleted the <5> at r6c6 thereby solving the puzzle. 
Ted |
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cathyv
Joined: 25 Apr 2008
Posts: 7
Location: Danbury, CT
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| Posted: Fri Apr 25, 2008 4:22 am Post subject: |
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Hi Norm - it's late, and I'm fairly new to the VH puzzles - but how did you remove the 2 from r1c4 and r8c6?
Thanks, Cathy |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Apr 25, 2008 5:05 am Post subject: |
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Cathy, welcome to the forum. Here's a position after basics:
| Code: |
+--------------+-----------------+----------------+
| 9 8 6 | 237 47 2347 | 23457 3457 1 |
| 5 14 7 | 18 168 2349 | 234 3468 249 |
| 2 3 14 | 5 168 479 | 47 4678 49 |
+--------------+-----------------+----------------+
| 8 9 5 | 6 3 1 | 247 47 24 |
| 137 24 24 | 9 57 8 | 135 135 6 |
| 1367 167 13 | 4 2 57 | 9 135 8 |
+--------------+-----------------+----------------+
| 17 25 28 | 1278 14578 6 | 14 9 3 |
| 36 256 239 | 123 1459 2345 | 8 14 7 |
| 4 17 389 | 1378 1789 37 | 6 2 5 |
+--------------+-----------------+----------------+
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Play this puzzle online at the Daily Sudoku site
There is an XYZ-Wing on 137 pivoted in r5c1. There is a W-Wing on the 47s in boxes 2 and 3. There is also another W-Wing on the 47s in boxes 3 and 6. Playing those moves and doing the eliminations therefrom will answer your question.
Since you're new here we don't know what terminology you may or may not be familiar with, so if there are still questions, please don't hesitate to ask. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Fri Apr 25, 2008 5:30 am Post subject: |
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Cathyv, HI!
you are probably more observant then what you think. in order to remove those 2's takes a move which is very hard to see. Have you heard of Sudoku Susser, or other programs that help locate moves?? if you haven't, then I suggest looking into it, it will help you get over obstacles like this. if you just want to know how those 2's disappear? then read on.
my grid above isn't the grid you would come up with directly after basics. the grid is after a UR on {6,8} in rows 2 and 3...
the grid below is directly after basics...with the UR marked as #
| Code: | 9 8 6 | 237 47 2347 | 23457 3457 1
5 4 7 | 18 #168 239 | 23 #68 29
2 3 1 | 5 #68 479 | 47 #68 49
------------------------------------------------------------------
8 9 5 | 6 3 1 | 247 47 24
17 2 4 | 9 57 8 | 135 135 6
6 17 3 | 4 2 57 | 9 15 8
------------------------------------------------------------------
17 5 28 | 1278 1478 6 | 14 9 3
3 6 29 | 12 1459 245 | 8 14 7
4 17 89 | 1378 1789 37 | 6 2 5 |
this UR eliminates the {6,8} in r2c5 and directly causes r2c5 to be solved as 1, which solves r2c4 as 8, which solves r2c8 as 6, then r3c8 as 8, then r3c5 as 6.
these are the singles that are found directly after the UR.
leaves you with this...
| Code: | 9 8 6 | 237 47 2347 | 23457 3457 1
5 4 7 | 8 1 239 | 23 6 29
2 3 1 | 5 6 479 | 47 8 49
------------------------------------------------------------------
8 9 5 | 6 3 1 | 247 47 24
17 2 4 | 9 57 8 | 135 135 6
6 17 3 | 4 2 57 | 9 15 8
------------------------------------------------------------------
17 5 28 |$127 *478 6 | 14 9 3
3 6 29 |$12 *459 *245 | 8 14 7
4 17 #89 | 137 *#789 37 | 6 2 5 |
in row 9 marked as #, you have a hidden pair on {8,9} which eliminates the 7 in r9c5
but more importantly in box 8 marked as * is a hidden quad on {4,5,8,9} which means that those four cells are the only cells that can contain {4,5,8,9}
this eliminates the 2 in r8c6 and 7 in r7c5, thus creating a pointing pair of 2's ( marked with $ )in column 4 which eliminates the 2 in r1c4.
everyone has a preference. I see hidden pairs easier than naked triples. I would have never seen this hidden quad without susser. I find this hidden quad in this example more appealing to find then the coinciding naked quad on 1,2,3,7 in the same box. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Fri Apr 25, 2008 6:15 pm Post subject: |
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To see a hidden pair ...
is almost impossible for me, relying only on PMs.
But...
in this case I found the hidden pair almost without lifting a finger. Take the rightmost "tower" (i.e. columns 7,8 and 9) in Marty's grid "after basics":
6 is already present in col 7 and col 9, in boxes 6 and 9. 6 is already present in row 1.
Thus: 6 must be in r23c8.
Same with 8: 8 must be in r23c8.
Two numbers which MUST be in two cellls: a hiddden pair. I mistakenly (bad memory, too) wrote naked pair in my post, but that was wrong.
Thus, the hidden pair 6,8 in col 8 came very early for me, long before the end of basics. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Fri Apr 25, 2008 6:25 pm Post subject: |
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| storm_norm wrote: | nataraj, go back to your w-wing grid... i see two w-wings on {4,7}
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Norm, now that you mention it, I see the second w-wing, too. I can't go back to my position, but going ahead from the one you posted, the second w-wing does not seem to solve the puzzle, I still need the kite.
Or, of course, Ted's very elegant xy-wing which works even without the w-wings. |
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cathyv
Joined: 25 Apr 2008
Posts: 7
Location: Danbury, CT
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| Posted: Fri Apr 25, 2008 8:50 pm Post subject: |
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| Thanks all - I had the UR but not the quads in box 8. Now I need to figure out w-wings........ |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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