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May 31 DB

 
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
PostPosted: Sat May 31, 2008 2:11 pm    Post subject: May 31 DB Reply with quote
The May 31 DB was an authentic VH for me. I had to color, do a few wings and then an xy-chain with a colored arm! Any one see a direct solution? I suspect this is one for the medusa people.


Earl


Code:

+-------+-------+-------+
| 4 . 8 | 6 . . | . 1 . |
| . . . | . 7 4 | . 3 . |
| . 6 . | . . 8 | . . . |
+-------+-------+-------+
| . . . | . . . | 7 9 . |
| . 2 9 | . . . | 1 5 . |
| . 8 7 | . . . | . . . |
+-------+-------+-------+
| . . . | 3 . . | . 8 . |
| . 5 . | 4 1 . | . . . |
| . 9 . | . . 7 | 5 . 2 |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sat May 31, 2008 5:06 pm    Post subject: Reply with quote
Code:
.---------------------.---------------------.---------------------.
| 4      37     8     | 6      2359  -2359  |*29     1      579   |
| 29     1      25    | 259    7      4     | 8      3      6     |
| 279    6     -235   | 1      2359   8     | 4     #27     579   |
:---------------------+---------------------+---------------------:
| 1356   34     134   | 25     2358   12356 | 7      9      38    |
| 36     2      9     | 7      48     36    | 1      5      48    |
| 135    8      7     | 59     3459   1359  | 26     26     34    |
:---------------------+---------------------+---------------------:
| 27     47     246   | 3      259    259   |*69     8      1     |
| 8      5     #26    | 4      1     *29    | 3    #*67     79    |
| 13     9      13    | 8      6      7     | 5      4      2     |
'---------------------'---------------------'---------------------'


present in the above grid is
marked # - xy-wing {2,6,7} removes 2 from r3c3
marked * - w-wing... (2,9) in r18c67 linked to strong links on 9 in box 9, eliminates 2 in r1c6...
these same cells also form a skyscraper on 9 and eliminate the 9 in r1c6

and a UR {3,6} in r45c16 removes 3's from r4c16 ( not much help)

amazing that the grid still holds after all of this.

leaves this...

Code:
.------------------.------------------.------------------.
| 4     37    8    | 6     2359  35   | 29    1     579  |
| 29    1     25   | 259   7     4    | 8     3     6    |
| 279   6     35   | 1     2359  8    | 4     27    579  |
:------------------+------------------+------------------:
| 156   34    134  | 25    2358  1256 | 7     9     38   |
| 36    2     9    | 7     48    36   | 1     5     48   |
| 135   8     7    | 59    3459  1359 | 26    26    34   |
:------------------+------------------+------------------:
| 27    47    246  | 3     259   259  | 69    8     1    |
| 8     5     26   | 4     1     29   | 3     67    79   |
| 13    9     13   | 8     6     7    | 5     4     2    |
'------------------'------------------'------------------'



the next xy-chain solves it

Code:
.------------------.------------------.------------------.
| 4    #37    8    | 6     2359 -35   | 29    1     579  |
| 29    1     25   | 259   7     4    | 8     3     6    |
| 279   6     35   | 1     2359  8    | 4     27    579  |
:------------------+------------------+------------------:
| 156  #34    134  | 25    2358  1256 | 7     9     38   |
|#36    2     9    | 7     48   #36   | 1     5     48   |
| 135   8     7    | 59    3459  1359 | 26    26    34   |
:------------------+------------------+------------------:
| 27   #47    246  | 3     259   259  | 69    8     1    |
| 8     5     26   | 4     1     29   | 3     67    79   |
| 13    9     13   | 8     6     7    | 5     4     2    |
'------------------'------------------'------------------'


xy-chain starting in r1c2 {37}-{47}-{34}-{36}-{36} ending in r5c6 eliminates the 3 in r1c6

so the key was to attack r1c6 with the coloring and a xy-chain
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat May 31, 2008 6:36 pm    Post subject: Reply with quote
I used the W-Wing on 29 and had a couple of ERs. From there, I went to Medusa and that trapped enough candidates to finish it off.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat May 31, 2008 7:42 pm    Post subject: Reply with quote
Norm,

Maybe a little simpler. You do not need the UR or the XY-wing. After basics:
Code:
+-------------------+-------------------+-------------------+
| 4     37A   8     | 6     2359  2359  | 29@   1     579   |
| 29    1     25    | 259   7     4     | 8     3     6     |
| 279   6     235   | 1     2359  8     | 4     27    579   |
+-------------------+-------------------+-------------------+
| 1356  34a   134   | 25    2358  12356 | 7     9     38    |
| 36b   2     9     | 7     48    36B   | 1     5     48    |
| 135   8     7     | 59    3459  1359  | 26    26    34    |
+-------------------+-------------------+-------------------+
| 27    47    246   | 3     259   259   | 69#   8     1     |
| 8     5     26    | 4     1     29@   | 3     67    79#   |
| 13    9     13    | 8     6     7     | 5     4     2     |
+-------------------+-------------------+-------------------+


The <29> pair which you used in the kite and in the W-wing are actually a remote pair. You can connect them by coloring on <9>, @-#-#-@. Taking out <29> in R1C6.

Then the kite aA and bB finishes it off by eliminating <3> in R1C6.

Keith

Last edited by keith on Sat May 31, 2008 8:22 pm; edited 1 time in total
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sat May 31, 2008 7:56 pm    Post subject: Reply with quote
Quote:
Maybe a little simpler


much simpler indeed.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
PostPosted: Sat May 31, 2008 8:17 pm    Post subject: Reply with quote
My solution path:
a) coloring (remove 3 from r1c6, r4c5, r6c5 and 9 from r1c6)
b) XYZ wing (2,7,9 in box 1 and row 3)
c) after some cleanup,W-wing:

Code:

+--------------------------+--------------------------+--------------------------+
| 4       37      8        | 6       2359    25       | 29*     1       579      |
| 29      1       25       | 259     7       4        | 8       3       6        |
| 279     6       35       | 1       2359    8        | 4       27      579      |
+--------------------------+--------------------------+--------------------------+
| 1356    34      134      | 25      258     136      | 7       9       38       |
| 36      2       9        | 7       48      36       | 1       5       48       |
| 135     8       7        | 59      459     13       | 26      26      34       |
+--------------------------+--------------------------+--------------------------+
| 27      47      246      | 3       25      259      | 69#     8       1        |
| 8       5       26       | 4       1       29*      | 3       67      79#      |
| 13      9       13       | 8       6       7        | 5       4       2        |
+--------------------------+--------------------------+--------------------------+



w-wing: 29 (r1c7 and r8c6) strong link 9 in box 9, solves r1c6=5
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat May 31, 2008 8:45 pm    Post subject: Reply with quote
Is there a systematic way to find 4-link chains?
Code:
+-------------------+-------------------+-------------------+
| 4     3*7#  8     | 6     2359  2359  | 29    1     5$7#9 |
| 29    1     25    | 259   7     4     | 8     3     6     |
| 279   6     3*5   | 1     2359  8     | 4     27    5$79  |
+-------------------+-------------------+-------------------+
| 1356  34    134   | 25    2358  12356 | 7     9     38    |
| 36    2     9     | 7     48    36    | 1     5     48    |
| 135   8     7     | 59    3459  1359  | 26    26    34    |
+-------------------+-------------------+-------------------+
| 27    47    246   | 3     259   259   | 69    8     1     |
| 8     5     26    | 4     1     29    | 3     67    79    |
| 13    9     13    | 8     6     7     | 5     4     2     |
+-------------------+-------------------+-------------------+

There is a strong link on 3 * in B1, one on 7 # in R1, and one on 5 $ in C9.

<3> in R1C2 forces 7 in R1C9, forces 5 in R3C9, forces <3> in R3C3. R1C2 cannot be <3>, the puzzle is solved.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat May 31, 2008 9:04 pm    Post subject: Reply with quote
Quote:
w-wing: 29 (r1c7 and r8c6) strong link 9 in box 9, solves r1c6=5

Didn't notice that connection, I used the 9s in column 9.
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