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Set H Puzzle 50

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daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Sat Jan 10, 2009 12:35 am Post subject: Set H Puzzle 50

Code:

+-----------------------+
| . . . | 7 2 . | 1 . 8 |
| . 6 . | 4 . 8 | . 7 . |
| . . . | . . 9 | . . . |
|-------+-------+-------|
| 4 7 . | . 9 . | . 6 . |
| 9 . . | 2 8 . | . . 5 |
| . 1 5 | . . 7 | . . . |
|-------+-------+-------|
| 1 . . | . . . | 2 . . |
| . 8 . | 1 . . | . 5 . |
| 6 . . | . 7 . | . . . |
+-----------------------+

Play this puzzle online at the Daily Sudoku site

===== ===== ===== ===== ===== ===== ===== ===== ===== ===== ===== ===== =====

Can be solved using steps from ...

Basics: Naked/Hidden Single, Naked Pair/Triple, Locked Candidate 1/2

Basics+: Naked Quad, Hidden Pair/Triple/Quad

VH: BUG+1, Remote Pair, UR Type 1, X-Wing, XY-Wing

Advanced: 2-String Kite, Empty Rectangle, Skyscraper, UR Type 2, XYZ-Wing

Extreme: finned X-Wing, M-Wing, W-Wing, XY-Chain

Extreme+: Swordfish, Jellyfish, (but mostly) Chain

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Sat Jan 10, 2009 8:24 pm Post subject:

A three-stepper but the first step did nothing.

Quote:

XYZ-Wing (234), ER (8 ) and Type 4 UR (89)

storm_norm

Joined: 18 Oct 2007
Posts: 1741

Posted: Sat Jan 10, 2009 9:19 pm Post subject:

Code:

.---------------------.---------------------.---------------------.
| 5 49 349 | 7 2 6 | 1 34 8 |
| 23 6 1 | 4 35 8 | 359 7 239 |
| 78 24 78 | 35 1 9 | 3456 234 2346 |
:---------------------+---------------------+---------------------:
| 4 7 28 | 35 9 135 | 38 6 123 |
| 9 3 6 | 2 8 14 | 7 14 5 |
| 28 1 5 | 6 34 7 | 3489 234(89) 2349 |
:---------------------+---------------------+---------------------:
| 1 459 3479 |U89 3456 345 | 2 34(89) 34679 |
| 237 8 23479 | 1 346 234 | 3469 5 34679 |
| 6 2459 2349 |U89 7 2345 | 3489 134(89) 1349 |
'---------------------'---------------------'---------------------'

notice the UR marked above on {8,9}

simply put... if candidate 8 and 9 do not exist in r6c8 then the UR is forced to exist...
therefore, any other candidates in r6c8 cannot exist, this eliminates the 2,3 and 4 from r6c8 and solves the puzzle.
-----

this alternative way of viewing the UR is, for my money, easier than noticing that the {1,3,4} naked triple in column 8 exists because of the UR.

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