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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sun Dec 21, 2008 8:07 am Post subject: 12/21 competition |
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| Code: |
+-------+-------+-------+
| 7 . . | . . 8 | . . 4 |
| 4 2 . | . . 5 | 6 . . |
| . 8 . | . . . | . 7 . |
+-------+-------+-------+
| . 1 . | . 2 . | . . . |
| . . . | 9 8 7 | . . . |
| . . . | . 5 . | . 3 . |
+-------+-------+-------+
| . 6 . | . . . | . 9 . |
| . . 3 | 7 . . | . 8 6 |
| 2 . . | . . 1 | . . 7 |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
good luck!
| Quote: | | keith's use of the psuedocell in a xy-wing extended is very very useful in this one. |
and today's fiendish vanhegan, if you are trying to do something to keep your brain warm.
| Code: |
+-------+-------+-------+
| . . . | . 2 . | 8 . . |
| . . . | . . 3 | 5 . . |
| 6 9 8 | 5 . 7 | 2 . . |
+-------+-------+-------+
| . 7 6 | 2 . 9 | 3 . . |
| 3 . . | . . . | . . 9 |
| . . 4 | 3 . 8 | 7 6 . |
+-------+-------+-------+
| . . 9 | 1 . 4 | 6 8 5 |
| . . 1 | 7 . . | . . . |
| . . 5 | . 9 . | . . . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Dec 21, 2008 5:30 pm Post subject: |
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I guess we are all looking for Keith's extended xy-wing pattern. After doing my normal single digit patterns first and finding three kites and one coloring deletion, I also spotted a extended xy-wing involving <45>, <24> and pseudo-cell <25> that provided five deletions. Another xy-wing finally did the deed for me.
I also found another extended xy-wing in this puzzle that did not have any deletions; pivot <24> at r7c6 with pincer <29> at r8c6 and pseudo-cell <49> in r6c16>.
I agree with Keith's comment in another thread that"extended xy-wing" is not a particularly good name; the word "Extended" has other uses. Perhaps use of the word "pseudo" or a variation thereof would be better.
Ted |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Dec 21, 2008 6:44 pm Post subject: |
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| I guess I should clarify that the pseudocell isn't contained in one box like the examples that keith has provided. instead the cells that form the pseudocell are in the same row. its a little rif on keith's concept. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Dec 21, 2008 6:55 pm Post subject: |
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| storm_norm wrote: | | I guess I should clarify that the pseudocell isn't contained in one box like the examples that keith has provided. instead the cells that form the pseudocell are in the same row. its a little rif on keith's concept. |
Norm,
The useless extended xy-wing I reported on above has the pseudo-cell in r6c16. In fact, the pattern has the pivot <24>, pincer <29> and one of the cells forming the pseudo-cell <49>, all in c6.
I that what you were referring too 
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sun Dec 21, 2008 9:44 pm Post subject: |
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| storm_norm wrote: | | I guess I should clarify that the pseudocell isn't contained in one box like the examples that keith has provided. instead the cells that form the pseudocell are in the same row. its a little rif on keith's concept. |
Keith's latest example has the pseudocell in [c1] ... and I took exception to it  |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Dec 22, 2008 2:29 am Post subject: |
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| Code: | .------------------.------------------.------------------.
| 7 3 156 |B26 19 8 | 259 C25 4 |
| 4 2 9 | 3 7 5 | 6 1 8 |
| 56 8 156 | 246 149 469 | 259 7 3 |
:------------------+------------------+------------------:
| 5689 1 4568 |A46 2 3 | 7 -456 59 |
| 3 45 2456 | 9 8 7 | 1245 2456 125 |
| 69 7 246 | 1 5 46 | 8 3 29 |
:------------------+------------------+------------------:
| 158 6 7 | 58 3 24 | 1245 9 125 |
| 15 45 3 | 7 49 249 | 1245 8 6 |
| 2 9 458 | 58 6 1 | 3 D45 7 |
'------------------'------------------'------------------' |
ok, what I conceive from Keith's examples is taking two cells that obviously have the same candidate present, and are bi-value, and using the other two candidates to help form ( and pivot) the xy-wing.
above please notice the cells marked A, B, C, D...
B and C have this connection, they both have the candidate 2 which tells that either 6 is true in B, or the 5 is true in C...
so... that makes a psuedocell (6,5) in row 1
now that forms a xy-wing with A and D,
(4=6)A - pseudo(6=5) - (5=4)D... this eliminates the 4 in r4c8...
basically, the concept just makes it a little easier to see the connections when you see some bi-value cells that almost make a xy-wing and Keith has picked up on this.
this is just a little something to keep an eye on for manual solvers if you aren't going to repeatedly pencil in marks. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Dec 22, 2008 6:41 pm Post subject: |
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the vanhegan fiendish...
| Code: | .------------------.------------------.------------------.
| 15 145 3 | 469 2 16 | 8 1479 1467 |
| 2 14 7 | 4689 68 3 | 5 149 146 |
| 6 9 8 | 5 14 7 | 2 134 134 |
:------------------+------------------+------------------:
| 15 7 6 | 2 145 9 | 3 14 8 |
| 3 8 2 | 46 7 16 | 14 5 9 |
| 9 15 4 | 3 15 8 | 7 6 2 |
:------------------+------------------+------------------:
| 7 2 9 | 1 3 4 | 6 8 5 |
| 48 36 1 | 7 68 5 | 9 2 34 |
| 48 36 5 | 68 9 2 | 14 1347 1347 |
'------------------'------------------'------------------' |
1. notice the 1's form a loop.
r1c1 = r4c1 - r6c2 = r6c5 - r3c5 = r1c6; r1c278 <> 1, and r4c5 <> 1
2. loop... (4=1)r9c7 - (1)r5c7 = (1-6)r5c6 = (6)r1c6 - (6=8)r2c5 - (8)r8c5 = (8)r9c4 - (8=4)r9c1; r9c89 <> 4
3. loop... (6=8)r2c5 - (8)r8c5 = (8)r9c4 - (8=4)r9c1 - (4)r9c7 = (4)r5c7 - (4=6)r5c4; r12c4 <> 6
4. w-wing(1,4)... (4=1)r2c2 - (1)r6c2 = (1)r6c5 - (1=4)r3c5; r2c4 <> 4
5. w-wing (1,4)... (4=1)r4c8 - (1)r4c1 = (1)r6c2 - (1=4)r2c2; r2c8 <> 4
6. xy-chain... (4=1)r4c8 - (1=9)r2c8 - (9=8)r2c4 - (8=6)r9c4 - (6=4)r5c4; r4c5 <> 4 |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Dec 22, 2008 8:26 pm Post subject: |
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the vanhegan fiendish ... is for Fishermen
| Code: | +--------------------------------------------------------------+
| 15 145 3 | 469 2 16 | 8 1479 1467 |
| 2 14 7 | 4689 68 3 | 5 149 146 |
| 6 9 8 | 5 14 7 | 2 134 134 |
|--------------------+--------------------+--------------------|
| 15 7 6 | 2 145 9 | 3 14 8 |
| 3 8 2 | 46 7 16 | 14 5 9 |
| 9 15 4 | 3 15 8 | 7 6 2 |
|--------------------+--------------------+--------------------|
| 7 2 9 | 1 3 4 | 6 8 5 |
| 48 36 1 | 7 68 5 | 9 2 34 |
| 48 36 5 | 68 9 2 | 14 1347 1347 |
+--------------------------------------------------------------+
# 49 eliminations remain
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| Code: | Franken Swordfish r236\c25b3 <> 1 [r1c289],[r4c5]
finned Franken X-Wing r4b2\c18 <> 1 [r2c8]
finned X-Wing r34\c58 <> 4 [r12c8]
XY-Wing [r1c6]/[r1c9]+[r3c5] <> 4 [r3c89]
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Alternate description:
| Code: | 1) Norm's loop on <1>
2) ER on <1>
3) finned X-Wing on <4>
4) <146> XY-Wing w/pivot [r1c6]
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Obviously, I didn't find this solution manually. Norm must be a glutton for punishment. 
[Addendum:] All of the eliminations on <1> can be found by successive applications of Colors and Multiple Colors for <1>. You can't use either approach to get around the critical finned X-Wing for <4>. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Dec 22, 2008 9:07 pm Post subject: |
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| Quote: | | Norm must be a glutton for punishment |
obviously since a xy-loop does the same as my steps 2 and 3, which I did not see before. |
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