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Oct 13 vh

 
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Sat Oct 13, 2007 9:15 am    Post subject: Oct 13 vh Reply with quote

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

PostPosted: Sat Oct 13, 2007 1:09 pm    Post subject: Reply with quote

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: 1110
Location: Dar es Salaam Tanzania

PostPosted: Sat Oct 13, 2007 5:09 pm    Post subject: Daily Sudoku Oct 13-2007 Reply with quote

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. Smile
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sdq_pete



Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL

PostPosted: Sat Oct 13, 2007 5:19 pm    Post subject: Reply with quote

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

PostPosted: Sat Oct 13, 2007 7:16 pm    Post subject: Reply with quote

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

PostPosted: Sat Oct 13, 2007 8:47 pm    Post subject: Reply with quote

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

PostPosted: Sat Oct 13, 2007 10:26 pm    Post subject: Reply with quote

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

PostPosted: Sun Oct 14, 2007 12:37 pm    Post subject: Reply with quote

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    |
 *-----------------------------------------------------------*


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

PostPosted: Sun Oct 14, 2007 4:53 pm    Post subject: Reply with quote

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    |
 *-----------------------------------------------------------*


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

PostPosted: Sun Oct 14, 2007 6:43 pm    Post subject: Reply with quote

Question
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Sun Oct 14, 2007 8:22 pm    Post subject: Reply with quote

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

PostPosted: Sun Oct 14, 2007 8:50 pm    Post subject: Reply with quote

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

PostPosted: Mon Oct 15, 2007 2:46 pm    Post subject: Reply with quote

An x-wing on 2(r39) forming an xy-wing (47,48,7Cool in boxes 3 and 6 was enough for me.
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