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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Sat Jan 03, 2009 7:57 am Post subject: A good Menneske |
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This one went on for a while ...
| Code: | Puzzle: M6852107sh(14)
+-------+-------+-------+
| . . . | . . . | 2 . 7 |
| . 4 2 | . . 5 | . 1 8 |
| 1 . . | 9 . . | . . . |
+-------+-------+-------+
| 4 . . | . 2 9 | . . 6 |
| . 5 . | 1 . 8 | . 3 . |
| . . . | 7 5 . | . . . |
+-------+-------+-------+
| 6 . . | . . 1 | . . 4 |
| . 2 . | 8 . . | 6 5 . |
| 8 3 . | . . . | . . . |
+-------+-------+-------+ |
Not for the faint of heart! Here is what Sudoku Susser says: | Quote: | 3 x Simple Forcing Chains
4 x Simple Forcing Loops
2 x XY-Wing
1 x Swordfish
1 x Comprehensive Naked Sets
1 x Intersection Removal
11 x Pinned Squares
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Keith |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Jan 03, 2009 4:30 pm Post subject: |
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| I gave up on this one - well actually I didn't. I know this is guessing - but it is "logical" guessing. I looked for a strong link where a 50:50 guess would do the most damage by getting rid of a number with the most clutter. In this case I placed the <7> in R9C8. The thing fell apart after that - nothing but singles!! |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Jan 03, 2009 4:43 pm Post subject: |
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| cgordon wrote: | | I gave up on this one - well actually I didn't. I know this is guessing - but it is "logical" guessing. I looked for a strong link where a 50:50 guess would do the most damage by getting rid of a number with the most clutter. In this case I placed the <7> in R9C8. The thing fell apart after that - nothing but singles!! |
That would be an Alternating Implication Cell? 
Keith |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Jan 03, 2009 4:47 pm Post subject: |
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After basics: | Code: | +----------------+----------------+----------------+
| 5 689 689 | 4 1 3 | 2 69 7 |
| 39 4 2 | 6 7 5 | 39 1 8 |
| 1 67 367 | 9 8 2 | 34 46 5 |
+----------------+----------------+----------------+
| 4 1 78 | 3 2 9 | 5 78 6 |
| 279 5 679 | 1 46 8 | 479 3 29 |
| 239 689 3689 | 7 5 46 | 1489 2489 129 |
+----------------+----------------+----------------+
| 6 79 5 | 2 3 1 | 789 789 4 |
| 79 2 1 | 8 49 47 | 6 5 3 |
| 8 3 4 | 5 69 67 | 179 279 129 |
+----------------+----------------+----------------+ |
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Jan 03, 2009 6:04 pm Post subject: |
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This was stubborn. M-Wing, Hidden UR, XY-Wing with coloring, multi-coloring, XY-Wing and W-Wing, both with coloring, and still it wouldn't break.
From the get-go it was obvious that this was a Medusa candidate and I finally resorted to it. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sat Jan 03, 2009 6:15 pm Post subject: |
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A tightly weaved succession of eliminations!
| Code: | after basics and not searching for URs
+--------------------------------------------------------------+
| 5 689 689 | 4 1 3 | 2 69 7 |
| 39 4 2 | 6 7 5 | 39 1 8 |
| 1 67 367 | 9 8 2 | 34 46 5 |
|--------------------+--------------------+--------------------|
| 4 1 78 | 3 2 9 | 5 78 6 |
| 279 5 679 | 1 46 8 | 479 3 29 |
| 239 689 3689 | 7 5 46 | 1489 2489 129 |
|--------------------+--------------------+--------------------|
| 6 79 5 | 2 3 1 | 789 789 4 |
| 79 2 1 | 8 49 47 | 6 5 3 |
| 8 3 4 | 5 69 67 | 179 279 129 |
+--------------------------------------------------------------+
# 54 eliminations remain (47 cells solved)
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| Code: | finned Swordfish r289\c157 w/fins [r9c89] => [r7c7]<>9 -or-
(9) r9c789 = r9c6 - r8c6 = r8c1 - r2c1 = r2c7 => [r7c7]<>9
(6=7)r3c2 - (7=9)r7c2 - (9=7)r8c1 - (7=4)r8c6 - (4=6)r6c6 => [r6c2]<>6 [XY-Chain]
XY-Wing [r7c2]/[r6c2]+[r7c7] => [r6c7]<>8
Swordfish r347\c238 => [r5c3],[r9c8]<>7
(9=6)r5c3 - (6=4)r5c5 - (4=9)r8c5 - (9=7)r8c1 - (7=9)r7c2 => [r6c2]<>9 [XY-Chain]
____________________________________________________________________________________
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Note: This puzzle has so many backdoor singles that it's a perfect candidate for Craig's approach (above). |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat Jan 03, 2009 11:53 pm Post subject: |
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this route will take some useless w-wings and extend them like rubber... after this coloring move on 9...
| Code: | .------------------.------------------.------------------.
| 5 689 689 | 4 1 3 | 2 69 7 |
|*39 4 2 | 6 7 5 |*39 1 8 |
| 1 67 367 | 9 8 2 | 34 46 5 |
:------------------+------------------+------------------:
| 4 1 78 | 3 2 9 | 5 78 6 |
| 279 5 679 | 1 46 8 | 479 3 29 |
| 239 689 3689 | 7 5 46 | 1489 2489 129 |
:------------------+------------------+------------------:
| 6 *79 5 | 2 3 1 |78-9 789 4 |
|*79 2 1 | 8 49 47 | 6 5 3 |
| 8 3 4 | 5 69 67 | 179 279 129 |
'------------------'------------------'------------------' |
step1... (9)... r2c7 = r2c1 - r8c1 = r7c2; r7c7 <> 9
| Code: | .------------------.------------------.------------------.
| 5 689 689 | 4 1 3 | 2 W69 7 |
| 39 4 2 | 6 7 5 | 39 1 8 |
| 1 67 *367 | 9 8 2 |*34 *46 5 |
:------------------+------------------+------------------:
| 4 1 78 | 3 2 9 | 5 78 6 |
| 279 5 679 | 1 *46 8 | 479 3 29 |
| 239 689 *3689 | 7 5 *46 | 1489 2489 129 |
:------------------+------------------+------------------:
| 6 79 5 | 2 3 1 | 78 W789 4 |
| 79 2 1 | 8 49 47 | 6 5 3 |
| 8 3 4 | 5 W69 67 |W179 W279 W129 |
'------------------'------------------'------------------' |
marked the W-wing {6,9}with W's... and then extended it on both sides...to eliminate the 6 in r6c3...
w-wing marked in red...
step2...(3)r6c3 = (3)r3c3 - (3=4)r3c7 - (4=6)r3c8 - (6=9)r1c8 - (9)r7c8 = (9)r9c789 - (9=6)r9c5 - (6)r5c5 = (6)r6c6; r6c3 <> 6
| Code: | .------------------.------------------.------------------.
| 5 689 689 | 4 1 3 | 2 69 7 |
| 39 4 2 | 6 7 5 | 39 1 8 |
| 1 W67 367 | 9 8 2 | 34 46 5 |
:------------------+------------------+------------------:
| 4 1 78 | 3 2 9 | 5 78 6 |
| 279 5 679 | 1 46 8 | 479 3 29 |
| 239 W689 389 | 7 5 W46 | 1489 2489 129 |
:------------------+------------------+------------------:
| 6 -79 5 | 2 3 1 | 78 789 4 |
|*79 2 1 | 8 49 *47 | 6 5 3 |
| 8 3 4 | 5 69 W67 | 179 279 129 |
'------------------'------------------'------------------' |
again, marked the W-wing {6,7} with W's and extended the 7's to eliminate the 7 in r7c2...
w-wing marked in red...
step3...(7=6)r3c2 - (6)r6c2 = (6)r6c6 - (6=7)r9c6 - (7)r8c6 = (7)r8c1; r7c2 <> 7 |
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