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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Sat Mar 13, 2010 6:13 pm Post subject: Free Press Mar 12, 2010 |
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Not yet done. | Code: | Puzzle: FP031210
+-------+-------+-------+
| . . . | 7 . 8 | . . . |
| 6 . . | . . . | 1 . 3 |
| . 4 . | . 5 . | . 2 . |
+-------+-------+-------+
| . . 5 | . 2 1 | . 7 . |
| 7 . . | . . . | . . 9 |
| . . . | 4 8 . | 5 . . |
+-------+-------+-------+
| . 3 . | . . . | . 9 . |
| 2 . 9 | . 6 . | . . 7 |
| . . . | 8 . 2 | . . . |
+-------+-------+-------+ |
Keith |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Mar 13, 2010 7:03 pm Post subject: |
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After skyscraper/kite in (6), this is where I found a potential DP:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 35 25 23 | 7 1 8 | 9 46 46 |
| 6 78 78 | 2 4 9 | 1 5 3 |
| 9 4 1 | 36 5 36 | 7 2 8 |
+--------------------------+--------------------------+--------------------------+
| 348 68 5 | 9 2 1 | 348 7 46 |
| 7 128 248 | 56 3 56 | 248 148 9 |
| 13 9 236 | 4 8 7 | 5 136 12 |
+--------------------------+--------------------------+--------------------------+
| 1458 3 468 | 15 7 45 | 2468 9 125 |
| 2 158 9 | 135 6 345 | 48 148 7 |
| 145 1567 467 | 8 9 2 | 346 134 15 |
+--------------------------+--------------------------+--------------------------+
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36-65-53 in cols 4 and 6
To prevent the DP, r8c46 must be 1 or 4 . Together with r8c78 this pseudocell forms a triple 148, which sets r8c2=5.
I also needed an m-wing later on - (2) r6c3=r5c7 using a SL in (6) in row 7: r6c9 and r5c3 cannot be "2". |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Mar 13, 2010 7:26 pm Post subject: |
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Nataraj,
Nice DP!
Keith |
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arkietech
Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
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| Posted: Sat Mar 13, 2010 8:34 pm Post subject: |
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A one stepper | Code: | *-----------------------------------------------------------*
| 35 25 23 | 7 1 8 | 9 46 46 |
| 6 78 78 | 2 4 9 | 1 5 3 |
| 9 4 1 | 36 5 36 | 7 2 8 |
|-------------------+-------------------+-------------------|
| 348 68 5 | 9 2 1 | 3468 7 46 |
| 7 128 248 | 56 3 56 | 248 148 9 |
| 13 9 236 | 4 8 7 | 5 136 12 |
|-------------------+-------------------+-------------------|
| 1458 3 468 | 15 7 45 | 2468 9 125 |
| 2 158 9 | 135 6 345 | 48 148 7 |
| 145 1567 467 | 8 9 2 | 346 1346 15 |
*-----------------------------------------------------------*
(6)r4c2=r9c2-r7c3=(6-2)r7c7=r7c9-r6c9=(2-6)r6c3=(6)r6c8;
r4c79,r6c3<>6 |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat Mar 13, 2010 9:21 pm Post subject: |
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| Quote: | | To prevent the DP, r8c46 must be 1 or 4 . Together with r8c78 this pseudocell forms a triple 148, which sets r8c2=5 |
of course this is excellent logic.
on the other side of the logic fence we have this way of looking at it.
notice how the 3's and the 6's are in a perfect x-wing.
this means that there exists no other 3's or 6's in the rows of the DP cells.
taking a look at the 5's, this isn't the case.
in row three we see that there is only two 5's, the DP 5's.
in row eight we see that there are three 5's. the DP 5's and a external 5 in r8c2.
the 5 in r8c2 has to be placed in order to avoid the DP. this is because if that 5 were eliminated then the DP would exist.
of course this does exactly the same thing as nataraj's logic tells us, but may come in handy if a locked set cannot be formed, or if some strong inference is useful in a chain. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Mar 13, 2010 10:21 pm Post subject: |
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| Excellent observation Norm. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Mar 14, 2010 3:54 pm Post subject: |
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Nataraj, I also started with the DP 356, but missed the subset 148. Instead, I extended the 1 & 4 to delete 5 in r79c1 forcing r1c1=5. Not nearly as useful as yours.
I also looked at the 6-cell DP 46 in r149c789 but could not work out any deletions.
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sun Mar 14, 2010 4:05 pm Post subject: |
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| storm_norm wrote: | | may come in handy if a locked set cannot be formed, or if some strong inference is useful in a chain. |
I like that logic. It is similar to the "type 3" unique rectangles.
Indeed, I seem to find more puzzles where the UR is either type 3 or has other strong links than those with any useful pseudocells... |
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