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DB Saturday Puzzle - October 7, 2006

 
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keith



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

PostPosted: Sat Oct 07, 2006 1:29 pm    Post subject: DB Saturday Puzzle - October 7, 2006 Reply with quote

Here it is. I won't be looking at it today.

Keith
Code:
Puzzle: DB100706  ******
+-------+-------+-------+
| . 5 . | . . . | . 9 . |
| 1 . . | 8 . 9 | . . . |
| 7 . . | 4 . . | . . 6 |
+-------+-------+-------+
| . 9 . | . 4 7 | 8 . 3 |
| . . . | . 3 . | . . . |
| 4 . 7 | 2 8 . | . 6 . |
+-------+-------+-------+
| 5 . . | . . 2 | . . 4 |
| . . . | 5 . 4 | . . 7 |
| . 6 . | . . . | . 3 . |
+-------+-------+-------+
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Marty R.



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

PostPosted: Sat Oct 07, 2006 3:27 pm    Post subject: Reply with quote

This one wasn't as challenging as the one two weeks ago. Basic stuff plus a couple of Type 4 rectangles, which I'm not sure were necessary for the solution. There was also a point at which I think remote pairs (25) could have been used, but they weren't necessary.
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TexCat



Joined: 07 Jul 2006
Posts: 32

PostPosted: Sat Oct 07, 2006 5:07 pm    Post subject: Reply with quote

My first Saturday without resorting to trial & error! Though it took me quite a while.
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Sat Oct 07, 2006 7:27 pm    Post subject: Reply with quote

Code:
 *-----------------------------------------------------------*
 | 23    5     23    | 167   17    16    | 4     9     8     |
 | 1     4     6     | 8     25    9     | 3     7     25    |
 | 7     8     9     | 4     25    3     | 125   125   6     |
 |-------------------+-------------------+-------------------|
 |@26    9    -125   |@16    4     7     | 8     125   3     |
 | 268  @12    1258  | 9     3     156   | 7     4     125   |
 | 4     3     7     | 2     8     15    | 159   6     159   |
 |-------------------+-------------------+-------------------|
 | 5     7     18    | 3    #69    2     |#69    18    4     |
 | 2389  12    1238  | 5    #169   4     |#1269  128   7     |
 | 29    6     4     | 17    179   8     | 1259  3     1259  |
 *-----------------------------------------------------------*
Many ways to solve it. In this situation either the xy-wing in the cells marked @ or the UR4 (marked #), which (because of the strong link of 6 in row 8) eliminates 9 from r8c57.
Additional:
This is also a UR3, because 12 are the extra candidates and we have 12 in r8c2, so 12 can be eliminated from r8c138.
Or: Since r8c2=12 and r8c8=128, 128 can be eliminated from r8c13.
And there is a UR4 for 23 in r18c13, which eliminates 2 from r8c13 (not a big help).
PS: I forgot to mention, that Simple Sudoku eliminates the 2 in r8c8 with coloring (r8c2-r5c2-r5c9-r4c8), but needed the xy-wing later.
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TexCat



Joined: 07 Jul 2006
Posts: 32

PostPosted: Sat Oct 07, 2006 10:08 pm    Post subject: Reply with quote

I solved it with the xy-wing. My first ever! I really find these hard to find.
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Marty R.



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

PostPosted: Sun Oct 08, 2006 5:19 am    Post subject: Reply with quote

TexCat wrote:
I solved it with the xy-wing. My first ever! I really find these hard to find.

Congratulations. Always great to use a technique for the first time. My biggest problem with the XY-Wing was always forgetting to look for them. I'll still miss SOME, but if I don't look, then I'll miss them ALL.
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