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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Sat Oct 13, 2007 9:15 am Post subject: Oct 13 vh |
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Not many obvious singles in the beginning (that's probably not a problem for those solving sudokus online). Then after spotting the "9" in r1c5 (c6 and r2 already contain 9), easy going up to here:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 1 8 45 | 2 9 6 | 47 3 457 |
| 24 7 9 | 3 5 1 | 248 6 248 |
| 3 25 6 | 4 7 8 | 1 9 25 |
+--------------------------+--------------------------+--------------------------+
| 8 6 245 | 9 1 27 | 247 245 3 |
| 9 1 3 | 58 4 27 | 6 25 278 |
| 7 45 245 | 58 6 3 | 248 1 9 |
+--------------------------+--------------------------+--------------------------+
| 24 3 1 | 7 8 9 | 5 24 6 |
| 5 9 7 | 6 2 4 | 3 8 1 |
| 6 24 8 | 1 3 5 | 9 7 24 |
+--------------------------+--------------------------+--------------------------+ |
so many bivalue cells, I am sure there will be many paths to the solution.
Mine was the chain r2c1=r7c1=r9c2=r9c9, call it w-wing, turbot whatever.
Anyway, it means that r2c9=8 and the rest was easy. |
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sdq_pete
Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL
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| Posted: Sat Oct 13, 2007 1:09 pm Post subject: |
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A single remote pair was enough to finish this one - see cells R9C9 and R2C1 with victim R2C9. Same as nataraj I guess.
Peter |
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Clement
Joined: 24 Apr 2006
Posts: 1113
Location: Dar es Salaam Tanzania
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| Posted: Sat Oct 13, 2007 5:09 pm Post subject: Daily Sudoku Oct 13-2007 |
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A hidden triple in column 7 i.e {4,7}r1, {2,4,8}r2, {2,4,7} {2,4,8} leaving 7 in r1c7 solves the puzzle.  |
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sdq_pete
Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL
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| Posted: Sat Oct 13, 2007 5:19 pm Post subject: |
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Er, are you sure, Clement? I see 4 unsolved cells in column 7 containing 4 candidate digits [2, 4, 7, 8] with no triple subset.
Peter |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Oct 13, 2007 7:16 pm Post subject: |
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| I used an x wing, an xyz wing and a skyscraper. I didn't find them easy to spot. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Oct 13, 2007 8:47 pm Post subject: |
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I used a Type 1 rectangle on 36, which I spotted but don't know was necessary, and remote pairs on 24 to solve r2c9.
Remote pairs is the common name of the technique that nataraj describes with his chain. |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Sat Oct 13, 2007 10:26 pm Post subject: |
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The remote pair Peter mentioned was the one step move collapsing the grid.
There was also an x-wing on <2> and an xy-wing with pivot in R2C9, which erases <7> in R1C9 and R4C7, solving the puzzle. |
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TKiel
Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI
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| Posted: Sun Oct 14, 2007 12:37 pm Post subject: |
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Here's the grid after the opening singles and the box/line interaction on <1> that leads to five more singles.
| Code: |
*-----------------------------------------------------------*
| 145 8 457 | 2 9 136 | 47 3456 457 |
| 124 1247 9 | 136 5 136 | 2478 2346 2478 |
| 3 25 6 | 4 7 8 | 1 9 25 |
|-------------------+-------------------+-------------------|
| 8 6 245 | 9 1 27 | 247 245 3 |
| 1259 1259 3 | 578 4 27 | 6 25 2578 |
| 7 245 245 | 3568 36 236 | 248 1 9 |
|-------------------+-------------------+-------------------|
| 24 2347 1 | 37 8 9 | 5 24 6 |
| 569 579 57 | 67 2 4 | 3 8 1 |
| 246 234 248 | 136 36 5 | 9 7 24 |
*-----------------------------------------------------------*
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W-wing using the <25> pair in boxes 3 & 6 solves it. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sun Oct 14, 2007 4:53 pm Post subject: |
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| TKiel wrote: | Here's the grid after the opening singles and the box/line interaction on <1> that leads to five more singles.
| Code: |
*-----------------------------------------------------------*
| 145 8 457 | 2 9 136 | 47 3456 457 |
| 124 1247 9 | 136 5 136 | 2478 2346 2478 |
| 3 25 6 | 4 7 8 | 1 9 25 |
|-------------------+-------------------+-------------------|
| 8 6 245 | 9 1 27 | 247 245 3 |
| 1259 1259 3 | 578 4 27 | 6 25 2578 |
| 7 245 245 | 3568 36 236 | 248 1 9 |
|-------------------+-------------------+-------------------|
| 24 2347 1 | 37 8 9 | 5 24 6 |
| 569 579 57 | 67 2 4 | 3 8 1 |
| 246 234 248 | 136 36 5 | 9 7 24 |
*-----------------------------------------------------------*
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Tracy,
Look for <36> in C79. So, there is a pair <36> in B3 which forms a UR with the two cells <136> in B2. Which takes out <1> in R2C4, which forms a triple <367> in C4 ...
Keith |
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TKiel
Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI
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| Posted: Sun Oct 14, 2007 6:43 pm Post subject: |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sun Oct 14, 2007 8:22 pm Post subject: |
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Tracy,
In the grid you posted there is a hiddden pair <36> in C8:
| Code: | *-----------------------------------------------------------*
| 145 8 457 | 2 9 136 | 47 36 457 |
| 124 1247 9 | 136 5 136 | 2478 36 2478 |
| 3 25 6 | 4 7 8 | 1 9 25 |
|-------------------+-------------------+-------------------|
| 8 6 245 | 9 1 27 | 247 245 3 |
| 1259 1259 3 | 578 4 27 | 6 25 2578 |
| 7 245 245 | 3568 36 236 | 248 1 9 |
|-------------------+-------------------+-------------------|
| 24 2347 1 | 37 8 9 | 5 24 6 |
| 569 579 57 | 67 2 4 | 3 8 1 |
| 246 234 248 | 136 36 5 | 9 7 24 |
*-----------------------------------------------------------* |
The <36> UR in R12C68 says that R2C4 is not <1>, which reveals a triple <367> in C4. R9C4 is <1>, etc.
Just an observation on the grid you posted (and, in fact, the way I solved it).
Keith |
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TKiel
Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI
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| Posted: Sun Oct 14, 2007 8:50 pm Post subject: |
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Keith,
Thanks for the clarification.
As the VH's sometimes seem not-so-hard lately, I've been trying to find that one move that turns everything to either naked or hidden singles after doing as few moves as possible (singles and box-line/box-box interactions only) at the start of the puzzle.
I believe this kind is called "One Trick Pony" on the other forum, which approaches it from the programmers POV, i.e. make a puzzle that can be solved with only one advanced technique after the basics vs. find the one advanced technique that solves this puzzle after the basics are done. |
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dulaby
Joined: 02 May 2007
Posts: 13
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| Posted: Mon Oct 15, 2007 2:46 pm Post subject: |
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An x-wing on 2(r39) forming an xy-wing (47,48,7 in boxes 3 and 6 was enough for me. |
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