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Free Press May 20, 2011

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keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Fri May 20, 2011 9:37 am Post subject: Free Press May 20, 2011

Not yet done. Requites advanced moves.

Code:

Puzzle: FP052011
+-------+-------+-------+
| . . . | 9 . . | . . 1 |
| . 9 4 | . . 8 | . . 2 |
| 2 . . | 6 . . | . . 7 |
+-------+-------+-------+
| . 1 . | 2 . . | . 5 . |
| 6 . 2 | . . . | 8 . 3 |
| . 3 . | . . . | . 1 . |
+-------+-------+-------+
| 1 . . | . . 6 | . . 9 |
| 5 . . | 4 . . | 6 3 . |
| 9 . . | . . 7 | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

Keith

Marty R.

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

Posted: Fri May 20, 2011 5:39 pm Post subject:

A short (four-cell) XY-Chain did it for me; 4 in r7c2 proves 8 in r4c3; r79c3<>8.

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Fri May 20, 2011 7:09 pm Post subject:

After basics:

Code:

+-------------------+-------------------+-------------------+
| 378 5678 568 | 9 3457 2 | 345 48 1 |
| 37 9 4 | 1357 1357 8 | 35 6 2 |
| 2 58 1 | 6 345 345 | 3459 489 7 |
+-------------------+-------------------+-------------------+
| 478 1 89 | 2 36789 39 | 79 5 46 |
| 6 57 2 | 157 14579 1459 | 8 79 3 |
| 478 3 589 | 578 56789 59 | 2 1 46 |
+-------------------+-------------------+-------------------+
| 1 48 38 | 358 2358 6 | 47 247 9 |
| 5 2 7 | 4 19 19 | 6 3 8 |
| 9 468 368 | 38 238 7 | 1 24 5 |
+-------------------+-------------------+-------------------+

Keith

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Fri May 20, 2011 8:02 pm Post subject:

Code:

+-------------------+-------------------+-------------------+
| 378 567-8 568 | 9 3457 2 | 345 48@ 1 |
| 37 9 4 | 1357 1357 8 | 35 6 2 |
| 2 58$ 1 | 6 345 345 | 3459 -489$ 7 |
+-------------------+-------------------+-------------------+
| 478 1 89 | 2 36789 39 | 79 5 46 |
| 6 57 2 | 157 14579 1459 | 8 79 3 |
| 478 3 589 | 578 56789 59 | 2 1 46 |
+-------------------+-------------------+-------------------+
| 1 48@ 38 | 358 2358 6 | 47 2-47 9 |
| 5 2 7 | 4 19 19 | 6 3 8 |
| 9 46-8# 368 | 38 238 7 | 1 24# 5 |
+-------------------+-------------------+-------------------+

The 48 cells @ are connected by strong links 4# and 8$: They are a double W-wing, and a remote pair. Further, the two W-wings form a closed cycle, all links are strong, and we can make the eliminations shown.

Leading to another loop:

Code:

+-------------------+-------------------+-------------------+
| 378 -567 568 | 9 3457 2 | 345 48 1 |
| 37 9 4 | 1357 1357 8 | 35 6 2 |
| 2 58@ 1 | 6 345 345 | 3459 89@ 7 |
+-------------------+-------------------+-------------------+
| 478 1 89 | 2 36789 39 | 79 5 46 |
| 6 57@ 2 |15-7 145-79 1459 | 8 79@ 3 |
| 478 3 589 | 578 56789 59 | 2 1 46 |
+-------------------+-------------------+-------------------+
| 1 48 38 | 358 2358 6 | 47 27 9 |
| 5 2 7 | 4 19 19 | 6 3 8 |
| 9 46 368 | 38 238 7 | 1 24 5 |
+-------------------+-------------------+-------------------+

Interesting moves, they do not solve the puzzle.

An M-wing is a single-stepper: 8 In R4C3 forces 8 in R3C8. R4C3 and R5C8 are pincers on 9, solving R4C7 as 7.

Keith

susume

Joined: 13 May 2011
Posts: 36
Location: Southeastern US

Posted: Sun May 22, 2011 7:51 pm Post subject:

A different single step approach involving 4 cells: Discontinuous nice loop [r1c3]=6=[r1c2]=7=[r5c2]=5=[r6c3]-5-[r1c3] => r1c3<>5

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