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Earl



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

PostPosted: Tue Jul 03, 2007 3:15 am    Post subject: Need Help Reply with quote

I could use help on this one.

Thanks

Earl

Code:

+---------+-----------+------------+
| 9 7  18 | 18 3   2  | 5    6  4  |
| 6 18 3  | 4  159 15 | 28   29 7  |
| 4 5  2  | 89 7   6  | 38   1  39 |
+---------+-----------+------------+
| 2 16 9  | 7  145 3  | 46   8  56 |
| 7 68 18 | 19 245 45 | 2346 35 39 |
| 3 4  5  | 6  29  8  | 7    29 1  |
+---------+-----------+------------+
| 5 9  47 | 2  146 14 | 36   37 8  |
| 8 2  47 | 3  46  9  | 1    57 56 |
| 1 3  6  | 5  8   7  | 9    4  2  |
+---------+-----------+------------+

Play this puzzle online at the Daily Sudoku site
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Tue Jul 03, 2007 5:10 am    Post subject: Reply with quote

After a W-wing with the 46's
a W-wing with the resulting 15's
a couple of X-wings on 1s
an X-wing on 9s

You end up here

Code:

+---------+---------+-----------+
|      18 | 18      |           |
|   18    |    19   | 28  29    |
|         | 89      | 38     39 |
+---------+---------+-----------+
|   16    |    15   |        56 |
|   68 18 | 19 25   | 236 35 39 |
|         |    29   |     29    |
+---------+---------+-----------+
|      47 |    46   | 36  37    |
|      47 |    46   |     57 56 |
|         |         |           |
+---------+---------+-----------+



From here I started coloring with R1C3 and ended up solving R5c7 which, pretty much
finished it off.
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Earl



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

PostPosted: Tue Jul 03, 2007 1:30 pm    Post subject: need help Reply with quote

jLo,

Thanks,

Is the grid you posted a BUG yielding a 3 in R5C7?

Earl
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Tue Jul 03, 2007 3:03 pm    Post subject: Reply with quote

Quote:

Is the grid you posted a BUG yielding a 3 in R5C7?


I hadn't noticed that, but yes it is.
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Tue Jul 03, 2007 6:38 pm    Post subject: Reply with quote

jLo's first W-Wing is also an XY-Chain.

There is another XY-Chain with pincers at R5C2 and R4C9 that eliminates <6> from R5C7.

These two XY-Chains solve the puzzle.

Nice to see the BUG+1!
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Earl



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

PostPosted: Tue Jul 03, 2007 8:03 pm    Post subject: Need Help Reply with quote

Asselius,

What is the difference between an "xy-chain" and an xy-wing"

Please explain slowly. I am a novice.

Thanks,

Earl
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Tue Jul 03, 2007 8:23 pm    Post subject: Reply with quote

XY Wing

http://www.sudoku9981.com/sudoku-solving/XY-Wing.asp

XY Wing

http://www.sudoku9981.com/sudoku-solving/XY-Chain.asp

An XY Wing is actually the shortest form of x-Y chain.
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Wed Jul 04, 2007 5:26 am    Post subject: Reply with quote

Quote:

jLo's first W-Wing is also an XY-Chain.

There is another XY-Chain with pincers at R5C2 and R4C9 that eliminates <6> from R5C7.



I don't see either of these chains. Can you give me the long version?
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Wed Jul 04, 2007 11:50 am    Post subject: Reply with quote

jLo wrote:
I don't see either of these chains. Can you give me the long version?


Not sure if this is the exact chain that Asellus used:

Code:
 
 *-----------------------------------------------------------*
 | 9     7     18c   | 18d   3     2     | 5     6     4     |
 | 6     18b   3     | 4     159   15    | 28    29    7     |
 | 4     5     2     | 89    7     6     | 38    1     39    |
 |-------------------+-------------------+-------------------|
 | 2     16    9     | 7     145   3     | 46    8     56j   |
 | 7     68a   18    | 19e   245   45    | 2346  35i   39h   |
 | 3     4     5     | 6     29f   8     | 7     29g   1     |
 |-------------------+-------------------+-------------------|
 | 5     9     47    | 2     146   14    | 36    37    8     |
 | 8     2     47    | 3     46    9     | 1     57    56    |
 | 1     3     6     | 5     8     7     | 9     4     2     |
 *-----------------------------------------------------------*


R5c2 shares <8> with r2c2, which leaves the <6> dangling. Now use the leftover digit in r2c2 <1> to link with another cell, in this case r1c3. The leftover digit there <8> links with r1c4. The chain is constructed in this manner, always alternating links, until another cell that has a <6> dangling is reached. When the two cells on the end of the chain have the same dangling digit and can both see a third cell that contains that digit, that digit can be eliminated from the third cell. In this case, the <6> in r5c7 and r4c2 can be eliminated.
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Wed Jul 04, 2007 1:21 pm    Post subject: Reply with quote

Quote:

Not sure if this is the exact chain that Asellus used:


OK, I see that one, but what about one that
links the 46 at R8C5 with the 46 at R4C7? That's
how I interpreted the post that said the W-wing
was also an XY-chain. Since the W-wing eliminates
a 4 at R4C5, the end's of the XY-chain would have
to be a 4 to do the same elimination. The partner
value of the 4 at R4C7 is a 6 which appears three
times in each row, column, and block that R4C7
is part of, which makes in un-linkable from my view.
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Wed Jul 04, 2007 5:26 pm    Post subject: Reply with quote

jLo wrote:
OK, I see that one, but what about one that
links the 46 at R8C5 with the 46 at R4C7?

Code:
 *-------------------------------------------*
 | 9  7   18  | 18  3    2   | 5     6   4   |
 | 6  18  3   | 4   159  15  | 28    29  7   |
 | 4  5   2   | 89  7    6   | 38    1   39  |
 |------------+--------------+---------------|
 | 2  16  9   | 7   145  3   |#46    8   56  |
 | 7  68  18  | 19  245  45  | 2346  35  39  |
 | 3  4   5   | 6   29   8   | 7     29  1   |
 |------------+--------------+---------------|
 | 5  9   47  | 2   146  14  |#36   #37  8   |
 | 8  2   47  | 3  #46   9   | 1    #57 #56  |
 | 1  3   6   | 5   8    7   | 9     4   2   |
 *-------------------------------------------*
Either r4c7=4
or (r4c7=6 => r7c7=3 => r7c8=7 => r8c8=5 => r8c9=6 =>) r8c5=4
=> r4c5<>4
Code:
 *------------------------------------------*
 | 9  7   18  | 18  3    2   | 5    6   4   |
 | 6 #18  3   | 4   159 #15  | 28   29  7   |
 | 4  5   2   | 89  7    6   | 38   1   39  |
 |------------+--------------+--------------|
 | 2 #16  9   | 7  #15   3   | 4    8   56  |
 | 7 #68  18  | 19  245  45  | 236  35  39  |
 | 3  4   5   | 6   29   8   | 7    29  1   |
 |------------+--------------+--------------|
 | 5  9   47  | 2   146  14  | 36   37  8   |
 | 8  2   47  | 3   46   9   | 1    57  56  |
 | 1  3   6   | 5   8    7   | 9    4   2   |
 *------------------------------------------*
Here there is an xy-wing (pivot r5c6), that eliminates 1 in r7c5, which leads to the BUG grid.
Or another xy-chain to eliminate 5 in r2c5:
Either r2c6=5
or (r2c6=1 => r2c2=8 => r5c2=6 => r4c2=1 =>) r4c5=5
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