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Earl
Joined: 30 May 2007 Posts: 677 Location: Victoria, KS
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Posted: Sat Jun 06, 2009 2:19 pm Post subject: June 6 DB |
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The June 6 DB was a two-stepper for me. (Norm will find a single shot.)
Solution: x-wing (6) opens an xy-wing (138)
Earl
Code: |
+-------+-------+-------+
| 2 . . | 3 . 6 | . . 1 |
| . . . | . 2 . | 4 9 6 |
| . . 5 | . . . | . . . |
+-------+-------+-------+
| 8 . . | . . 3 | . 2 . |
| . 4 . | . . . | . 3 . |
| . 5 . | 2 . . | . . 7 |
+-------+-------+-------+
| . . . | . . . | 9 . . |
| 3 9 4 | . 1 . | . . . |
| 6 . . | 9 . 7 | . . 5 |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site |
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Louise56
Joined: 21 Sep 2005 Posts: 94 Location: El Cajon, California USA
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Posted: Sat Jun 06, 2009 2:44 pm Post subject: |
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I solved it the same way that Earl did. I must be getting better at these. I could not solve last weeks puzzle. I tried it 3 times and could not do it. |
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storm_norm
Joined: 18 Oct 2007 Posts: 1741
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Posted: Mon Jun 08, 2009 5:07 am Post subject: |
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this isn't the easiest one step, but its always interesting to find.
Code: | .---------------.---------------.---------------.
| 2 8 9 | 3 4 6 | 7 5 1 |
| 1 3 7 | 58 2 58 | 4 9 6 |
| 4 6 5 | 1 7 9 | 23 8 23 |
:---------------+---------------+---------------:
| 8 1 6 | 7 9 3 | 5 2 4 |
| 7 4 2 | 68 5 1 | 68 3 9 |
| 9 5 3 | 2 68 4 | 168 16 7 |
:---------------+---------------+---------------:
| 5 7 *18 | 4 368 *28 | 9 16 *238 |
| 3 9 4 | 568 1 258 | 26 7 28 |
| 6 2 *18 | 9 *38 7 |*1-3 4 5 |
'---------------'---------------'---------------' |
focusing on the marked cells in the bottom third of the puzzle.
Code: | +--------+---------+----------+
| . . 18 | . . 28 | . . 238 |
| . . . | . . . | . . . |
| . . 18 | . 38 . | 13 . . |
+--------+---------+----------+ |
notice how there can be a xy-wing made if the 8 in r7c9 is false.
looks like this: (imagine this in your head)
Code: | +--------+---------+---------+
| . . 18 | . . *28 | . .*23 |
| . . . | . . . | . . . |
| . . 18 | .*38 . | 13 . . |
+--------+---------+---------+ |
see the xy-wing? it eliminates the 3 in r9c7, keep this in mind.
now lets say the xy-wing is false
looks like this:(imagine this in your head)
Code: | +--------+-------+--------+
| . . 18 | . . . | . . 8 |
| . . . | . . . | . . . |
| . . 18 | . . . | 13 . . |
+--------+-------+--------+ |
r7c9 = 8, leads to r9c3 is 8, leads to r9c7=1, r9c7 is not 3.
see how the 3 can't exist in r9c7?? sound familiar?? either way the 3 doesn't exist in r9c7
bingo!
xy-wing[(38)r9c5, (28)r7c6, (23)r7c9] = (8)r7c9 - (8)r7c3 = (8-1)r9c3 = (1)r9c7; r9c7 <> 3
either the xy-wing exists means r9c7 <> 3
or the 1 exists in r9c7, means r9c7 <> 3
Last edited by storm_norm on Mon Jun 08, 2009 6:17 pm; edited 1 time in total |
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Marty R.
Joined: 12 Feb 2006 Posts: 5770 Location: Rochester, NY, USA
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Posted: Mon Jun 08, 2009 3:23 pm Post subject: |
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Quote: | there you have a nice "almost xy-wing".
this way of using a xy-wing that is almost there is not new, there are posters in the players forum who employ it. |
Norm,
This was discussed here some months ago and was given the name "Finned XY-Wing." I don't think many here have used it, or at least, there hasn't been much talk about it since. I personally try to avoid it, but have no quarrel with its use. |
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keith
Joined: 19 Sep 2005 Posts: 3355 Location: near Detroit, Michigan, USA
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Posted: Mon Jun 08, 2009 5:02 pm Post subject: |
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There is a 4-cell chain (extended XY-wing) 16 13 38 68 which takes out <6> in R6C8 and solves the puzzle.
Keith |
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storm_norm
Joined: 18 Oct 2007 Posts: 1741
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Posted: Mon Jun 08, 2009 6:18 pm Post subject: |
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Marty R. wrote: | Quote: | there you have a nice "almost xy-wing".
this way of using a xy-wing that is almost there is not new, there are posters in the players forum who employ it. |
Norm,
This was discussed here some months ago and was given the name "Finned XY-Wing." I don't think many here have used it, or at least, there hasn't been much talk about it since. I personally try to avoid it, but have no quarrel with its use. |
thanks Marty,
I was wondering if this wasn't discussed here or not. I do remember the discussions on the finned xy-wing but didn't follow it as closely as I should have.
I took out the mentions of it being a almost xy-wing. |
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