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garytorborg
Joined: 19 Jan 2011
Posts: 28
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 Posted: Fri Mar 04, 2011 8:11 pm Post subject: Honing my skills |
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Last time I posted a puzzle on which I was stuck, the solution ended up being a couple of (rather long) chains. I have since done much practicing in that regard and have found it to be quite a satisfying technique. However, after several puzzles that I was able to solve quickly, I have run into another "fiendish" puzzle.
This one has already had a couple of chains, both of which resulted in a few eliminations. The eliminations resulted in exposing some naked pairs, which then resulted in more eliminations... but precious few actual solved cells. After basics, 2 chains, and some more basics, I have this:
| Code: |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 8 | 1 | 46 | 5 | 2 | 37 | 37 | 46 | 9 |
| 569 | 2 | 3 | 8 | 4679| 46 | 457 | 1 | 4567|
| 56 | 7 | 4569| 39 | 146 | 146 | 8 | 2 | 3456|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 4 | 56 | 568 | 7 | 568 | 9 | 1 | 3 | 2 |
| 1 | 9 | 567 | 2 | 3 | 456 | 457 | 8 | 457 |
| 2 | 3 | 578 | 1 | 458 | 458 | 6 | 9 | 457 |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 379 | 45 | 1 | 6 | 79 | 37 | 2 | 45 | 8 |
| 356 | 456 | 2569| 39 | 158 | 1258| 3459| 7 |13456|
| 3567| 8 | 2569| 4 | 157 | 125 | 359 | 56 | 1356|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+ |
What am I missing?
Last edited by garytorborg on Fri Mar 04, 2011 9:17 pm; edited 1 time in total |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Fri Mar 04, 2011 9:05 pm Post subject: |
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Gary, it looks to me like a whole bunch of basics not done??
For a start you have r8c5=752 yet there is a 2 solved in c5 and a 7 solved in r8. |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Fri Mar 04, 2011 9:16 pm Post subject: |
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| peterj wrote: | Gary, it looks to me like a whole bunch of basics not done??
For a start you have r8c5=752 yet there is a 2 solved in c5 and a 7 solved in r8. |
oops
The cell in question was entered incorrectly. The cell contains the candidates 158, not 752. Perhaps I need to brush up on my proofreading as well  .
I will edit the above diagram. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Fri Mar 04, 2011 9:45 pm Post subject: |
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After more basics: | Code: | +----------------+----------------+----------------+
| 8 1 46 | 5 2 37 | 37 46 9 |
| 569 2 3 | 8 4679 46 | 457 1 4567 |
| 569 7 4569 | 39 1469 146 | 8 2 3456 |
+----------------+----------------+----------------+
| 4 56 568 | 7 568 9 | 1 3 2 |
| 1 9 567 | 2 3 456 | 457 8 457 |
| 2 3 578 | 1 458 458 | 6 9 457 |
+----------------+----------------+----------------+
| 39 45 1 | 6 79 37 | 2 45 8 |
| 3569 456 2569 | 39 158 1258 | 49 7 146 |
| 7 8 2569 | 4 15 125 | 39 56 136 |
+----------------+----------------+----------------+ |
| Quote: | | Look for an X-wing |
Keith |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Fri Mar 04, 2011 9:50 pm Post subject: |
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Kieth:
You actually have some additional 9's that I've already eliminated. There is an X-wing on 9s in R2C15, R7C15, eliminating the 9s from cells R3C1 and R3C5 and R8C1. |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Fri Mar 04, 2011 9:53 pm Post subject: |
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| Also: how did you solve the 7 in R9C1? I don't see it. |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Fri Mar 04, 2011 9:55 pm Post subject: |
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| Oops... I spotted it. Partially hidden quad in box 8. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Fri Mar 04, 2011 10:18 pm Post subject: |
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| garytorborg wrote: | | Also: how did you solve the 7 in R9C1? I don't see it. |
OK, let's reset the puzzle: | Code: | +-------------------+-------------------+-------------------+
| 8 1 46 | 5 2 3467 | 347 46 9 |
| 569 2 3 | 8 4679 467 | 457 1 4567 |
| 569 7 4569 | 39 1469 1346 | 8 2 3456 |
+-------------------+-------------------+-------------------+
| 4 56 568 | 7 568 9 | 1 3 2 |
| 1 9 567 | 2 3 456 | 457 8 457 |
| 2 3 578 | 1 458 458 | 6 9 457 |
+-------------------+-------------------+-------------------+
| 3579 45 1 | 6 579 357 | 2 45 8 |
| 3569 456 24569 | 39 1589 12358 | 3459 7 13456 |
| 35679 8 25679 | 4 1579 12357 | 359 56 1356 |
+-------------------+-------------------+-------------------+ |
After pairs 45, 46, and 37, there is a triple 379 in B8: | Code: | +-------------------+-------------------+-------------------+
| 8 1 46 | 5 2 37 | 37 46 9 |
| 569 2 3 | 8 4679 46 | 457 1 4567 |
| 569 7 4569 | 39 1469 146 | 8 2 3456 |
+-------------------+-------------------+-------------------+
| 4 56 568 | 7 568 9 | 1 3 2 |
| 1 9 567 | 2 3 456 | 457 8 457 |
| 2 3 578 | 1 458 458 | 6 9 457 |
+-------------------+-------------------+-------------------+
| 379 45 1 | 6 79 37 | 2 45 8 |
| 3569 456 2569 | 39 158 1258 | 349 7 1346 |
| 35679 8 2569 | 4 15 125 | 39 56 136 |
+-------------------+-------------------+-------------------+ |
R9C1 is the only 7 in R9.
Keith |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Sat Mar 05, 2011 11:21 am Post subject: |
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A flightless w-wing(56) r4c2, r9c8 with transport (6)r1 now does some damage...
Still more work but you can take your pick of xy-chains. |
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JV
Joined: 09 Jan 2011
Posts: 24
Location: Devon, England
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| Posted: Mon Mar 07, 2011 4:04 pm Post subject: |
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After the 9s X-wing, the 7s pointing pair in box8, & clearing up box 2:
| Code: |
+--------------+-------------+-------------+
| 8 1 46 | 5 2 37 | 37 46 9 |
| 569 2 3 | 8 79 46 | 457 1 4567 |
| 56 7 459-6| 39 146 146 | 8 2 3456 |
+--------------+-------------+-------------+
| 4 56 568 | 7 568 9 | 1 3 2 |
| 1 9 567 | 2 3 456 | 457 8 457 |
| 2 3 578 | 1 458 458 | 6 9 457 |
+--------------+-------------+-------------+
| 39 45 1 | 6 79 37 | 2 45 8 |
| 356 456 2569 | 39 158 1258 | 49 7 146 |
| 7 8 2569 | 4 15 125 | 39 56 136 |
+--------------+-------------+-------------+
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Play this puzzle online at the Daily Sudoku site
There's a kite that clears the 6 in r3c3.
Several identical pairs moves.
(5=6)r3c1 - r1c3 = r1c8 - (6=5)r9c8-r7c8 = r7c2; r8c1 <> 5 (This is actually just an xy-chain.)
Now, r3c3 = 49, and that forms a w-wing in 4s with r8c7. It just needs extendiing:
(4)r8c7 = r3c3 - r1c3 = r1c8; r2c7 <> 4, r7c8 <> 4. I think this is enough to finish, but there is another move of a kind recently discussed.
The 39s of r3c4 & r8c7 are 'remote pairs' because they're connected by 3s - i.e. they're conjugate. So you can extend EACH end by one, as Keith pointed out recently, and get (9)r8c4 = r8c7; r8c3 <>9. Or, you can explain it in sundry other ways. Don't think it's needed anyway! |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Mar 07, 2011 5:15 pm Post subject: |
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Given the initial confusion, I started my solver with the solved cells from the original grid. After removing extraneous steps:
| Code: | +-----------------------+
| 8 1 . | 5 2 . | . . 9 |
| . 2 3 | 8 . . | . 1 . |
| . 7 . | . . . | 8 2 . |
|-------+-------+-------|
| 4 . . | 7 . 9 | 1 3 2 |
| 1 9 . | 2 3 . | . 8 . |
| 2 3 . | 1 . . | 6 9 . |
|-------+-------+-------|
| . . 1 | 6 . . | 2 . 8 |
| . . . | . . . | . 7 . |
| . 8 . | 4 . . | . . . |
+-----------------------+
after basics
*-----------------------------------------------------------*
| 8 1 46 | 5 2 37 | 37 46 9 |
| 569 2 3 | 8 4679 46 | 457 1 4567 |
| 569 7 4569 | 39 1469 146 | 8 2 3456 |
|-------------------+-------------------+-------------------|
| 4 56 568 | 7 568 9 | 1 3 2 |
| 1 9 567 | 2 3 456 | 457 8 457 |
| 2 3 578 | 1 458 458 | 6 9 457 |
|-------------------+-------------------+-------------------|
| 39 45 1 | 6 79 37 | 2 45 8 |
| 3569 456 2569 | 39 158 1258 | 49 7 146 |
| 7 8 2569 | 4 15 125 | 39 56 136 |
*-----------------------------------------------------------*
r27 X-Wing <> 9 r3c15,r8c1
XY-Chain: (6=4)r1c3 =6r1c8 =5r9c8 =4r7c8 =5r7c2 =6r4c2 => r45c3<>6
XY-Chain: (4=6)r1c8 =4r1c3 =9r3c3 =3r3c4 =9r8c4 =4r8c7 => r7c8<>4
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An interesting extraneous step after the X-Wing:
| Code: | Sashimi Franken Swordfish r15b2\c36b3 <> 6 r3c39
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Mon Mar 07, 2011 8:40 pm Post subject: |
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| Once again, WOW. And, thanks to all of you for helping with this. |
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