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Puzzle 10/04/18 (C)

 
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Sun Apr 18, 2010 4:39 pm    Post subject: Puzzle 10/04/18 (C) Reply with quote
Code:
 +-----------------------+
 | 2 . . | . . . | . 1 . |
 | . . . | 3 . 5 | . . . |
 | . . 4 | . 9 1 | . . . |
 |-------+-------+-------|
 | . 1 . | . . . | . . 3 |
 | . . 5 | . 1 3 | . . 8 |
 | . 9 3 | . 5 6 | 1 2 . |
 |-------+-------+-------|
 | . . . | . . 8 | 6 . 9 |
 | 3 . . | . . 9 | . 8 . |
 | . . . | 6 3 . | 7 . 5 |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site

Hint wrote:
XYZ-Wing possible.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Sun Apr 18, 2010 9:39 pm    Post subject: Reply with quote
I initially started this puzzle looking at URs.

UR47 in r78c25 forces r7c2=25 or r8c2=6
(2)r7c2 - r7c3 = r4c3 - (2=8)r4c5 - (8=6)r1c5 - (6=7)r1c9,
||
(5)r7c2 - r1c2 = r1c7 - (5=7)r3c8,
||
(6)r8c2 - (6=7)r2c2.
Thus r2c8<>7
Also, this UR47 has a strong link 4 in r8c25 that allows deletion of 7 in r7c2.

Now, look at the outside row implication of the UR53 r13c27.
Digit 3: None
Digit 5: r3c18
Thus to prevent the deadly pattern, one of r3c18 must be 5 so that r3c27<>5.

After all that fun but no results, I returned to standard VH steps.
Quote:
xy-wing 26-7 with vertex 26 in r2c5; r3x12<>7,

Another Kraken xyz-wing 678 in r2c3
(6)r2c3; r3c2<>6
||
(7)r2c3 - (7=6)r2c2; r3c2<>6
||
(8)r2c3 - r2c7 = (8-3)r3c7 = (3)r1c7 - r1c2 = (3)r3c2; r3c2<>6

Finally, a xy-wing 2-78 with vertex 28 in r4c5 completes the puzzle.

I suspect the first three UR related deletions were not needed.
Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Tue Apr 20, 2010 4:56 am    Post subject: Reply with quote
W-Wing (67)

Type 4 UR (35), but better results were achieved by creating a pincer situation with the two DP killers

W-Wing (47)
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Tue Apr 20, 2010 4:59 am    Post subject: Reply with quote
W-Wing (67)

Type 4 UR (35), but better results were achieved by creating a pincer situation with the two DP killers

W-Wing (47)

Quote:
UR47 in r78c25 forces r7c2=25 or r8c2=6
(2)r7c2 - r7c3 = r4c3 - (2=8)r4c5 - (8=6)r1c5 - (6=7)r1c9,
||
(5)r7c2 - r1c2 = r1c7 - (5=7)r3c8,
||

Ted, what does that symbol ll mean?
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