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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Mon Apr 26, 2010 5:07 am Post subject: Puzzle 10/04/26 (A) |
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| Code: | +-----------------------+
| 3 . . | 7 . 4 | . . . |
| . 8 . | . 3 9 | 1 . 4 |
| . . 2 | . . . | . . . |
|-------+-------+-------|
| 6 . . | . 4 . | . . . |
| . 2 . | 6 7 . | . 4 . |
| 9 4 . | . . . | 3 . . |
|-------+-------+-------|
| . 5 . | . . 7 | 6 9 . |
| . . . | . 6 . | 7 . 2 |
| . 6 . | . . . | . 3 8 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site
[Edit: altered title and dropped unrealistic second puzzle.] |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Apr 27, 2010 12:50 am Post subject: |
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| Quote: | Type 1 UR (34)
XY-Wing (157) |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Apr 27, 2010 6:26 pm Post subject: |
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Here is another example of the "luck of the draw" or "which step next".
I started with the type 1 UR34 in r78c34 which set r8c3=9. Here is the resulting code after minimual cleanup.
| Code: | *--------------------------------------------------------------------*
| 3 19 156 | 7 1258 4 | 2589 268 569 |
| 57 8 567 | 25 3 9 | 1 267 4 |
| 4 179 2 | 158 158 6 | 589 78 3 |
|----------------------+----------------------+----------------------|
| 6 17 13578 | 9 4 12358 | 258 128 57 |
| 15 2 1358 | 6 7 1358 | 589 4 59 |
| 9 4 1578 | 1258 1258 1258 | 3 1268 567 |
|----------------------+----------------------+----------------------|
| 28 5 4 | 3 28 7 | 6 9 1 |
| 18 3 9 | 4 6 18 | 7 5 2 |
| 127 6 17 | 125 9 125 | 4 3 8 |
*--------------------------------------------------------------------* |
I then noticed the xy-wing 1-57 with vertex in 17 in r4c2 that deleted 5s in r4c3 & r5c79.
After further cleanup, I notice another xy-wing 15-7 with vertex 15 in r5c1 that deleted 7 in r3c2 to complete the puzzle. Upon looking back to the code after the UR34, I found that this second xy-wing 15-7 was also available then and, in fact, involved two of the same bivalue cells.
So here is an example of two xy-wing involving three identical bivalues that make different deletions; one makes multiple deletions but is useless, and the other makes a single deletion to complete the puzzle.
So which one is the lucky choice?
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Apr 27, 2010 8:27 pm Post subject: |
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Ted: It's not uncommon for my solver to report concurrent instances of a technique and only one of them be needed to proceed. My biggest headache is dealing with extraneous X-Wings.
| Code: | r78c34 <34> UR Type 1.2223 r8c3<>34
<17+5> XY-Wing r4c2/r4c9+r5c1 <> 5 r4c3,r5c79 extraneous
<15+7> XY-Wing r5c1/r2c1+r4c2 <> 7 r3c2
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If you enjoyed the extraneous XY-Wing in this puzzle, then you're going to love puzzle 27(A). |
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