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Can you find an M-wing?

 
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.

PostPosted: Mon Jul 14, 2008 7:25 am    Post subject: Can you find an M-wing? Reply with quote

This puzzle is a hoot. (Jsudoku generated.)

It starts of nicely and then nearly every step is advanced.
Expect to see: 2-string kites, finned and plain x-wings, ERs, finned sword, UR4, xy-wing and W-wings, unless you find the M-wing. Oh, if you miss the M-wing add xyz and sashimi sword, at least.

It is possible to ruin the M-wing without using a W-wing. An extra W-wing saves the day. Good hunting!

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



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Jul 14, 2008 8:42 am    Post subject: Reply with quote

my shortest path,

coloring 4
UR
xy-wing


Code:
.---------------------.---------------------.---------------------.
| 1      5      49    | 3      2      479   | 467    467    8     |
| 3      469    8     | 45679  56     4679  | 1      2      47    |
| 7      46     2     | 46     1      8     | 9      5      3     |
:---------------------+---------------------+---------------------:
| 2      1      37    | 467    8      5     | 467    3467   9     |
| 6      379    379   | 1      47     2     | 8      347    5     |
| 4      8      5     | 679    3      679   | 67     1      2     |
:---------------------+---------------------+---------------------:
| 9      2      147   | 4567   56     1467  | 3      8      47    |
| 8      47     6     | 2      9      3     | 5      47     1     |
| 5      347    1347  | 8      47     147   | 2      9      6     |
'---------------------'---------------------'---------------------'
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS

PostPosted: Mon Jul 14, 2008 2:08 pm    Post subject: M wing Reply with quote

Coloring on 4, then the brute force of an xy-chain does it.

Earl
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nataraj



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

PostPosted: Tue Jul 15, 2008 6:40 am    Post subject: Reply with quote

I did find an m-wing right after basics, but it did not solve the puzzle. So I went the coloring way (on 4)
Code:

+--------------------------+--------------------------+--------------------------+
| 1       5       49       | 3       2       479      | 467     467     8        |
| 3       469     8        | 45679   56      4679     | 1       2       47       |
| 7       46      2        | 46      1       8        | 9       5       3        |
+--------------------------+--------------------------+--------------------------+
| 2       1       37       | 467     8       5        | 467     3467    9        |
| 6       379     379      | 1       47      2        | 8       347     5        |
| 4       8       5        | 679     3       679      | 67      1       2        |
+--------------------------+--------------------------+--------------------------+
| 9       2       147      | 4567    56      1467     | 3       8       47       |
| 8       47      6        | 2       9       3        | 5       47      1        |
| 5       347     1347     | 8       47      147      | 2       9       6        |
+--------------------------+--------------------------+--------------------------+


4 can be removed from r2c2 (same as the m-wing), r2c4, r2c6, and (!) from r4c4 by a very long chain:
4:-r4c7=r1c7-r2c9=r7c9-r8c8=r8c2-r3c2=r3c4-;r4c4<>4
Code:

+·····+·····+·····+
·    9·    o·* o  ·
·     ·     ·|    ·
·  o  ·o   o·|   7·
·     ·     ·|   |·
·  6---6    ·|   |·
+·····+·····+|···|+
·     ·*    ·* o |·
·     · \   ·    |·
·     ·  7-----* |·
·     ·  |  ·    |·
·     ·  |  ·    |·
+·····+··|··+····|+
·    o·o | o·    7·
·     ·  |  ·   / ·
·  7-----------7  ·
·     ·  |  ·     ·
·  o o·  7 o·     ·
+·····+·····+·····+


After cleanup and (once more) coloring on 4 (simple skyscraper cols 2 and 4 this time), this is where a w-wing becomes very useful (again no m-wing):

Code:

+--------------------------+--------------------------+--------------------------+
| 1       5       49       | 3       2      -49       | 67      67      8        |
| 3       69      8        | 5679    56#     679      | 1       2       4        |
| 7       46      2        | 46*     1       8        | 9       5       3        |
+--------------------------+--------------------------+--------------------------+
| 2       1       37       | 67      8       5        | 4       367     9        |
| 6       39      379      | 1       4       2        | 8       37      5        |
| 4       8       5        | 679     3       679      | 67      1       2        |
+--------------------------+--------------------------+--------------------------+
| 9       2       1        |-456     56#     46*      | 3       8       7        |
| 8       7       6        | 2       9       3        | 5       4       1        |
| 5       34      34       | 8       7       1        | 2       9       6        |
+--------------------------+--------------------------+--------------------------+


Where IS that elusive m-wing?
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.

PostPosted: Tue Jul 15, 2008 10:36 am    Post subject: Reply with quote

nataraj wrote:

Where IS that elusive m-wing?


"#" marks the strong links on 7 for the basic pattern.
"@" marks the strong links on 4 for the pointing arm.
"*" marks the target and 4 is eliminated.
Code:
+-------------------+-------------------+-------------------+
| 1     5     49    | 3     2     79    | 467   67    8     |
| 3     69    8     | 47@   5     69    | 1     2     47@   |
| 7    *6-4   2     | 46@   1     8     | 9     5     3     |
+-------------------+-------------------+-------------------+
| 2     1     37    | 67    8     5     | 467   3467  9     |
| 6     379   379   | 1     4     2     | 8     37    5     |
| 4     8     5     | 9     3     67    | 67    1     2     |
+-------------------+-------------------+-------------------+
| 9     2    #17    | 5     6     14    | 3     8    #47@   |
| 8    #47    6     | 2     9     3     | 5     47    1     |
| 5     34    134   | 8     7     14    | 2     9     6     |
+-------------------+-------------------+-------------------+
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Tue Jul 15, 2008 1:00 pm    Post subject: Reply with quote

Code:
.---------------------.---------------------.---------------------.
| 1      5     *49    | 3      2      479   |*467   *467    8     |
| 3      69     8     | 4579   56     4679  | 1      2     @47    |
| 7     @46     2     | 46     1      8     | 9      5      3     |
:---------------------+---------------------+---------------------:
| 2      1      37    | 467    8      5     | 467    3467   9     |
| 6      379    379   | 1      47     2     | 8      347    5     |
| 4      8      5     | 679    3      679   | 67     1      2     |
:---------------------+---------------------+---------------------:
| 9      2      14-7  | 457    56     1467  | 3      8     #47    |
| 8     #47     6     | 2      9      3     | 5      4-7    1     |
| 5      347    1347  | 8      47     147   | 2      9      6     |
'---------------------'---------------------'---------------------'
Nice puzzle.
After the remote naked pair 47 to eliminate 4 from r2c2 and the UR 56 (r27c4<>6) there is a w-wing 47 connected by a grouped kite in 4, which takes out 7 from r7c3 and r8c8. An xy-wing then solves it.

Did not see the M-wing either - needs the elimination of 4 in r1c6 (??). Suppose, this would be called remote naked pair (or kite or - using r7c3 - an M-wing) with pincer coloring or transport here.

[Added:]btw, I liked todays wapati on the programmers forum very much, i had 4 types of UR, a kite, a w-wing connected with a grouped link and an xy-wing.
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nataraj



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

PostPosted: Thu Jul 17, 2008 9:43 pm    Post subject: Reply with quote

Thanks, wapati, for pointing out the m-wing. I did not look further than to look for a simple strong link (for the pointing arm), but of course any (even multi-) coloring chain will do...

nice!
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