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Minimal Pencil Marks

 
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Mon Jul 21, 2008 9:11 pm    Post subject: Minimal Pencil Marks Reply with quote
Try doing this one with minimal pencil marks. You should not need PM's in any cell that has more than two candidates.
Code:
Puzzle: M4819719sh(7)
+-------+-------+-------+
| . 9 . | . . 6 | . . 3 |
| 2 . . | . 1 . | . . . |
| . . . | 2 4 . | 8 . 9 |
+-------+-------+-------+
| 8 . . | . . . | . . 2 |
| . . 5 | . . . | 3 . . |
| 1 . 9 | . . . | 6 . 7 |
+-------+-------+-------+
| 6 . 7 | 9 8 . | . . . |
| . . . | . 3 . | . . 1 |
| 5 . . | . . 1 | . 4 . |
+-------+-------+-------+
Keith
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Tue Jul 22, 2008 9:43 pm    Post subject: Reply with quote
No takers on this one?

Crying or Very sad

After only singles, and showing only solved and two-candidate cells:
Code:
+---------+----------+----------+
| 47 9 14 | 8  57 6  | .  2  3  |
| 2  . .  | 3  1  9  | 45 .  46 |
| 3  . 16 | 2  4  57 | 8  .  9  |
+---------+----------+----------+
| 8  . .  | .  .  .  | .  .  2  |
| 47 . .  | .  .  .  | 3  .  48 |
| 1  . .  | 45 25 .  | 6  58 7  |
+---------+----------+----------+
| 6  1 7  | 9  8  4  | 2  3  5  |
| 9  . .  | 56 3  25 | 7  68 1  |
| 5  . .  | 67 .  1  | 9  4  68 |
+---------+----------+----------+
There are two XY-wings that you do not need.

Note the <57> pair in B2, and the <25> cells in C56. They make a W-wing! The only place for <2> in C6 is R8C6, and the puzzle is solved.

Keith
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