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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Sat Oct 07, 2006 1:29 pm Post subject: DB Saturday Puzzle - October 7, 2006 |
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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
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| Posted: Sat Oct 07, 2006 3:27 pm Post subject: |
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| 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
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| Posted: Sat Oct 07, 2006 5:07 pm Post subject: |
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| 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
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| Posted: Sat Oct 07, 2006 7:27 pm Post subject: |
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| 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 |
*-----------------------------------------------------------*
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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
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| Posted: Sat Oct 07, 2006 10:08 pm Post subject: |
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| 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
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| Posted: Sun Oct 08, 2006 5:19 am Post subject: |
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| 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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