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Puzzle XY 09/12/02

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daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Thu Dec 03, 2009 3:34 am Post subject: Puzzle XY 09/12/02

Code:

+-----------------------+
| 7 . . | . . . | . . . |
| . 4 6 | . 9 . | 7 . . |
| . 9 3 | 8 . . | . . 6 |
|-------+-------+-------|
| . . 9 | 4 7 . | 2 . . |
| . 7 . | 9 3 8 | . . 5 |
| . . . | . 2 6 | 8 . . |
|-------+-------+-------|
| . 6 . | 7 . 9 | 1 . 2 |
| . . . | . . . | . . 4 |
| . . 5 | . 8 . | 9 6 . |
+-----------------------+

Play this puzzle online at the Daily Sudoku site

Marty R.

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

Posted: Thu Dec 03, 2009 5:37 am Post subject:

XY-Wing (345) with two pincer transports, Type 1 UR (13), ER (5)and W-Wing (45).

storm_norm

Joined: 18 Oct 2007
Posts: 1741

Posted: Fri Dec 04, 2009 1:35 am Post subject:

might be an easier one stepper out there but here is one I saw.

Code:

+------------------+-------------------+---------------------+
| 7 12(5) 12 | 2356 1456 1234 | (345) 9 8 |
| 8 4 6 | 235 9 123 | 7 (1235) (13) |
| 12(5) 9 3 | 8 15(4) 7 | 5(4) (125) 6 |
+------------------+-------------------+---------------------+
| 6 8 9 | 4 7 5 | 2 13 13 |
| 12 7 12 | 9 3 8 | 6 4 5 |
| (35) 35 4 | 1 2 6 | 8 7 9 |
+------------------+-------------------+---------------------+
| 4(3) 6 8 | 7 (45) 9 | 1 -5(3) 2 |
| 9 123 7 | 2356 156 123 | 35 8 4 |
| 1234 123 5 | 23 8 1234 | 9 6 7 |
+------------------+-------------------+---------------------+

here is the oversized chain...
[(3)r7c8=(3)r7c1-(3=5)r6c1-(5)r3c1=(5)r1c2-(5=4)r1c7-(4)r3c7=(4)r3c5-(4=5)r7c5]=(3)r1c7 - ALS[(3)r2c89 = (25)r23c8]r23c89; r7c8 <> 5

explanation...

this chain would eliminate the 5 in r7c8 if the 3 in r1c7 is false...
chain #1...(3)r7c8=(3)r7c1-(3=5)r6c1-(5)r3c1=(5)r1c2-(5=4)r1c7-(4)r3c7=(4)r3c5-(4=5)r7c5

if the 3 in r1c7 is true
this 3 sets off a ALS inference in box 3
(3)r1c7 - ALS[(3)r2c89 = (25)r23c8]r23c89.
that {2,5} set would eliminated the 5 in r7c8.

so regardless if chain #1 is true or false, the 5 can't exist in r7c8

picture form

diagram ==> r7c8 <> 5

(5)r7c1 - (5)r1c2 = (5)r3c1 - (5=3)r6c1 - (3)r7c1 = (3)r7c8
||
(4)r1c7 - (4)r3c7 = (4)r3c5 - (4=5)r7c5
||
(3)r1c7 - ALS[(3)r2c89 = (25)r23c8]r23c89

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