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June 12 Hard

 
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Jun 12, 2016 1:15 pm    Post subject: June 12 Hard Reply with quote

Code:

+--------------+----------+---------------+
| 4   7    15  | 6  35 9  | 138 2   18    |
| 6   2359 259 | 8  1  45 | 34  7   49    |
| 139 39   8   | 7  34 2  | 6   5   149   |
+--------------+----------+---------------+
| 7   49   149 | 3  8  45 | 2   6   1459  |
| 129 249  3   | 19 45 6  | 7   489 14589 |
| 5   8    6   | 19 2  7  | 14  49  3     |
+--------------+----------+---------------+
| 23  1    24  | 5  7  8  | 9   34  6     |
| 39  3459 459 | 2  6  1  | 348 348 7     |
| 8   6    7   | 4  9  3  | 5   1   2     |
+--------------+----------+---------------+

Play this puzzle online at the Daily Sudoku site

having solved it Via a simple XY wing 345 pivoted at r2c6, I went back to the beginning since it must be soluble by "simple fundamentals"

So at the "critical point" I found another hard solution that I don't recognise as a formal one. Whether r3c1 or r3c8 is 1 r3c5 becomes 4 very quickly and that solves it.

The draw play solutions move (cannot explain) is to set r3c1 to 1 which solves it _ I cannot see the logic for this move!

HELP


Last edited by George Woods on Sun Jun 12, 2016 6:35 pm; edited 1 time in total
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sun Jun 12, 2016 1:37 pm    Post subject: Reply with quote

Quote:
I Have forgotten how to copy a puzzle int0 this text ANYWAY


George,

In Draw/Play you click the Ascii button to the right of the grid. A small window will appear. Click in the window and then copy with Ctrl/C, then Paste into the message box.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Jun 12, 2016 6:36 pm    Post subject: Reply with quote

thanks Marty I have put the critical point into my question
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sun Jun 12, 2016 7:50 pm    Post subject: Reply with quote

Boy, that was driving me nuts George! I finally noticed that the 9's in c9 of box 3 are locked so they can be removed from r45c9 and the 4's in r6 of box 6 are locked so they can also be removed from r45c9 - and that leaves the hidden 49 pair in r23c9 (which removes the 1 from r3c9) which leaves the lone 1 in r3 at r3c1! Good one!
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sun Jun 12, 2016 8:39 pm    Post subject: Reply with quote

You can start off with the 4s in r6 locked in b6 and after the eliminations in r45c9 then the c9 4s are locked in b3 => -4r2c7=3r2c7=> 18 pair in r1c79.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Jun 12, 2016 9:20 pm    Post subject: a type of XY wing Reply with quote

Thanks for the non wing solutions

In reply to my own implied question that sets r3c5 to 4

We have a kind of XY wing 153 pivot r1c3 the only departure from norm is that if the pivot is 1 it creates a 3 in box1 row 3 either c1 or c2 - i.e. two wings of 3 bear down on r3c5 which therefore cannot be 3

Is this move called an XY or an extended XY or what?
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sun Jun 12, 2016 10:43 pm    Post subject: Reply with quote

Quote:
We have a kind of XY wing 153 pivot r1c3 the only departure from norm is that if the pivot is 1 it creates a 3 in box1 row 3 either c1 or c2 - i.e. two wings of 3 bear down on r3c5 which therefore cannot be 3

Is this move called an XY or an extended XY or what?




Code:
+--------------+----------+---------------+
| 4   7    15  | 6  35 9  | 138 2   18    |
| 6   2359 259 | 8  1  45 | 34  7   49    |
| 139 39   8   | 7  34 2  | 6   5   149   |
+--------------+----------+---------------+
| 7   49   149 | 3  8  45 | 2   6   1459  |
| 129 249  3   | 19 45 6  | 7   489 14589 |
| 5   8    6   | 19 2  7  | 14  49  3     |
+--------------+----------+---------------+
| 23  1    24  | 5  7  8  | 9   34  6     |
| 39  3459 459 | 2  6  1  | 348 348 7     |
| 8   6    7   | 4  9  3  | 5   1   2     |
+--------------+----------+---------------+


It's certainly not an extended XY. Some people use that term when there are three identical bivalue cells in a chain which serve as a pivot cell. Such as 13-15-15-15-35. I do not see two wings which bear down on r3c5.

Maybe this is an XY-Wing with a pseudo cell, as r3c12 act as a single 13 cell. Or maybe a grouped wing.

The right person to answer your question is Keith and I'm sure he will if he sees this.
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keith



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

PostPosted: Wed Jun 15, 2016 12:19 am    Post subject: Reply with quote

Marty R. wrote:
The right person to answer your question is Keith and I'm sure he will if he sees this.

I'm not so sure. I am also not in favor of complicated solutions when simpler will suffice.

At the start:
Code:
+-------------------+-------------------+-------------------+
| 4     357   157   | 6     357   9     | 138   2     18    |
| 6     23579 2579  | 378   1     4578  | 348   34789 489   |
| 139   379   8     | 37    347   2     | 1346  5     1469  |
+-------------------+-------------------+-------------------+
| 7     2459  12459 | 139   8     145   | 1245  6     1459  |
| 1259  2459  3     | 19    459   1456  | 7     1489  14589 |
| 159   8     14569 | 179   2     14567 | 145   149   3     |
+-------------------+-------------------+-------------------+
| 238   1     247   | 5     7     78    | 9     348   468   |
| 23589 23459 2459  | 1289  6     18    | 13458 1348  7     |
| 589   6     579   | 4     79    3     | 158   18    2     |
+-------------------+-------------------+-------------------+

After 11 singles:
Code:
+-------------------+-------------------+-------------------+
| 4     7     15    | 6     35    9     | 138   2     18    |
| 6     2359  259   | 8     1     45    | 34    7     49    |
| 139   39    8     | 7     34    2     | 6     5     149   |
+-------------------+-------------------+-------------------+
| 7     459   1459  | 3     8     45    | 2     6     1459  |
| 1259  2459  3     | 19    45    6     | 7     1489  14589 |
| 159   8     6     | 19    2     7     | 145   149   3     |
+-------------------+-------------------+-------------------+
| 23    1     24    | 5     7     8     | 9     34    6     |
| 3589  3459  459   | 2     6     1     | 3458  348   7     |
| 58    6     7     | 4     9     3     | 158   18    2     |
+-------------------+-------------------+-------------------+

we get to intersections. After only a couple of those, we get here:

Code:
+----------------+----------------+----------------+
| 4    7    15   | 6    35   9    | 138  2    18   |
| 6    2359 259  | 8    1    45   | 34   7    49   |
| 139  39   8    | 7    34   2    | 6    5    149  |
+----------------+----------------+----------------+
| 7    459  1459 | 3    8    45   | 2    6    15   |
| 1259 2459 3    | 19   45   6    | 7    189  158  |
| 159  8    6    | 19   2    7    | 145  149  3    |
+----------------+----------------+----------------+
| 23   1    24   | 5    7    8    | 9    34   6    |
| 3589 3459 459  | 2    6    1    | 3458 348  7    |
| 58   6    7    | 4    9    3    | 158  18   2    |
+----------------+----------------+----------------+

The triple 158 or hidden pair 49 in C9 solves it.

Keith
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