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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Tue Feb 15, 2011 3:57 am Post subject: Puzzle 11/02/14 |
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| Code: | +-----------------------+
| 7 3 . | . 6 4 | . . . |
| 6 4 . | 5 2 . | . . . |
| . . . | . . 7 | . 5 . |
|-------+-------+-------|
| . 7 . | 3 . . | . . . |
| 5 8 . | . 1 2 | 3 6 . |
| 2 . 3 | . 8 6 | . 7 . |
|-------+-------+-------|
| . . . | . 4 . | 5 2 . |
| . . 2 | . 7 3 | 6 1 . |
| . . . | . . . | . . 7 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Wed Feb 16, 2011 10:52 pm Post subject: |
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The tubot opened it up and looked like a BUG might crack it - but no BUG there?
| Code: | skyscraper(4) c3, c8 ; r4c1<>4, r5c9<>4
m-wing-like(18) ; (83=1)r72c9 - r1c9=(1-8)r1c4=r8c4 ; r7c6<>8, r8c9<>8 |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Thu Feb 17, 2011 12:28 am Post subject: |
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What the ~!#$%^&*
I just found something that I don't recall seeing previously.
My solver found Peter's M-Wing, but I thought it was simply because my solver doesn't know how to perform a BUG+2. After reading Peter's comment, I decided to examine the puzzle closer. Here's what I noticed:
| Code: | point of Peter's M-Wing
+-----------------------------------------------------+
| 7 3 5 | 189 6 4 | 28 89 12 |
| 6 4 19 | 5 2 89 | 7 389 13 |
| 8 2 19 | 19 3 7 | 4 5 6 |
|-----------------+-----------------+-----------------|
| 1 7 6 | 3 9 5 | 28 48 24 |
| 5 8 4 | 7 1 2 | 3 6 9 |
| 2 9 3 | 4 8 6 | 1 7 5 |
|-----------------+-----------------+-----------------|
| 39 1 7 | 6 4 89 | 5 2 38 |
| 49 5 2 | 89 7 3 | 6 1 48 |
| 34 6 8 | 2 5 1 | 9 34 7 |
+-----------------------------------------------------+
# 23 eliminations remain
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| Code: | *) 3x 8s in [r1], [c8], and [b3]
*) 3x 9s in [r2], [c4], and [b2]
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Now, place r1c8=9 and you get:
| Code: | *) 2x 8s in [r1], [c8], and [b3]
*) 2x 9s in [r2], [c4], and [b2]
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Everything now looks like a BUG pattern, but the result is zero solutions instead of a multiple of 2x solutions.
If you think about it, zero is a multiple of two. Maybe there is a BUG scenario present after all. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Feb 17, 2011 5:44 am Post subject: |
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I used my typical excess moves.
Type 1 UR (59)
XY-Wing (891), flightless with transport
Skyscraper (4)
Type 4 UR (28)
XY-Wing (348), flightless with transport |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Thu Feb 17, 2011 8:37 am Post subject: |
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| daj95376 wrote: | What the ~!#$%^&*
Now, place r1c8=9 and you get: |
Weird!
So there is a zero-solution BUG that is prevented by placing a value in a bivalue cell r1c8<>9=8?
As you say putting a 9 in there seems to create a BUG so it has to be an 8.
Perhaps there is one of these oddagon/brokenwing type illegal patterns in here somewhere? |
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ronk
Joined: 07 May 2006
Posts: 398
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| Posted: Thu Feb 17, 2011 11:23 am Post subject: |
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The no-solution possibility was included in the ancient (2005/2006) BUG theorem.
| here Jeff wrote: | Theorem:
BUG grids can have either zero or more than one solution, and so are incompatible with a unique solution puzzle. |
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