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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Mon Nov 26, 2007 5:29 am Post subject: Stuck |
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This is a Vanhegan Fiendish rated 2.4.1.2:
| Code: |
+----------------+----------------+-----------------+
| 39 7 5 | 8 1 6 | 23 4 239 |
| 148 189 2 | 49 459 3 | 6 589 7 |
| 348 389 6 | 2 7 459 | 35 3589 1 |
+----------------+----------------+-----------------+
| 5 6 3 | 7 49 1 | 8 2 49 |
| 7 129 19 | 36 8 24 | 345 359 3456 |
| 29 4 8 | 5 36 29 | 7 1 36 |
+----------------+----------------+-----------------+
| 1238 12389 149 | 3469 3569 4589 | 2345 7 23458 |
| 6 238 7 | 1 345 458 | 9 35 23458 |
| 38 5 49 | 349 2 7 | 1 6 348 |
+----------------+----------------+-----------------+
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Play this puzzle online at the Daily Sudoku site
The original:
| Code: |
+-------+-------+-------+
| . 7 5 | 8 1 . | . 4 . |
| . . 2 | . . 3 | 6 . 7 |
| . . . | . . . | . . . |
+-------+-------+-------+
| . 6 3 | . . 1 | 8 2 . |
| . . . | . 8 . | . . . |
| . 4 8 | 5 . . | 7 1 . |
+-------+-------+-------+
| . . . | . . . | . . . |
| 6 . 7 | 1 . . | 9 . . |
| . 5 . | . 2 7 | 1 6 . |
+-------+-------+-------+
|
Play this puzzle online at the Daily Sudoku site |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Nov 26, 2007 11:57 am Post subject: |
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I think Medusa coloring does the trick. I just did it on paper, only now I have to re-create the reasoning ....
Noticing the very long chain in "9"s I started there:
| Code: |
+·····+·····+·····+
·g---------------r·
·| · · |·
·| o ·o o · o |·
·| · · |·
·| o · o· o |·
+|····+·····+····|+
·| · r-------g·
·| · \ · / ·
·| o o· | · r ·
·| · \ · ·
·r---------g· ·
+·····+·····+·····+
· o o·o o o· ·
· · · ·
· · · ·
· · · ·
· *-* · ·
+·····+·····+·····+
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If g is true, then neither r3c2 nor r3c6 can be 9, which makes r3c8=9
If r is true, then r1c9=9
Either way, r2c8<>9
This does not yet solve the puzzle, but we're getting there.
More after a short break ... |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Nov 26, 2007 2:01 pm Post subject: |
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I've now added the medusa coloring in boxes 5 and 6,
we move into "4"s:
| Code: |
+----------------+----------------+-----------------+
| 39 7 5 | 8 1 6 | 23 4 239r |
| 148 189 2 | 49 459 3 | 6 589 7 |
| 348 389 6 | 2 7 459 | 35 3589 1 |
+----------------+----------------+-----------------+
| 5 6 3 | 7 4g9r 1 | 8 2 4r9g |
| 7 129 19 | 36 8 2g4r | 345 359 3456 |
| 29 4 8 | 5 36 2r9g | 7 1 36 |
+----------------+----------------+-----------------+
| 1238 12389 149 | 3469 3569 4589 | 2345 7 23458 |
| 6 238 7 | 1 345 *458 | 9 35 23*458|
| 38 5 49 | 349 2 7 | 1 6 348 |
+----------------+----------------+-----------------+
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If red is true, neither r8c6 nor r8c9 can be 4, hence r8c5=4
But if green is true, r4c5=4, so we can remove 4 from r2c5.
Next: the incredible elimination of 5 from r2c8...
(maybe tonight. don't have time now) |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon Nov 26, 2007 4:24 pm Post subject: |
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In the starting grid you have a UR 19.
| Code: | +------------------+----------------+-----------------+
| 39 7 5 | 8 1 6 | 23 4 239 |
| 148 189 2 | 49 459 3 | 6 589 7 |
| 348 389 6 | 2 7 459 | 35 3589 1 |
+------------------+----------------+-----------------+
| 5 6 3 | 7 49 1 | 8 2 49 |
| 7 #129 #19 | 36 8 24 | 345 359 3456 |
| 2*9 4 8 | 5 36 29 | 7 1 36 |
+------------------+----------------+-----------------+
|*1238 #12389 #149 | 3469 3569 4589 | 2345 7 23458 |
| 6 238 7 | 1 345 458 | 9 35 23458 |
| 38 5 4*9 | 349 2 7 | 1 6 348 |
+------------------+----------------+-----------------+
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One of the starred digits has to be true. From all of them follows r5c3=1 (r7c1=1 => r7c3<>1).
A w-Wing 49 follows, but is no great help either.
I used 4 strong links in 4 (r2c6<>4) and then a 6 cell chain (with a pair) to eliminate 5 from r2c8 (and r3c6).
After that still advanced techniques including 3 strong links were needed. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Nov 26, 2007 4:57 pm Post subject: |
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| Thanks. You guys have confirmed that it's a tough one. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Nov 26, 2007 8:39 pm Post subject: |
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Marty, you're welcome.
It seems to be a tough one all right.
continuing from where I left off this afternoon, with 4 and 9 gone from r2c5 and r2c8, respectively,
| Code: |
+----------------+----------------+-----------------+
| 39 7 5 | 8 1 6 | 23 4 239r |
| 148 189 2 | 49 *59 3 | 6 5*8 7 |
| 348 389 6 | 2 7 459 | 35 3589g 1 |
+----------------+----------------+-----------------+
| 5 6 3 | 7 4g9r 1 | 8 2 4r9g |
| 7 129 19 | 36 8 2g4r | 345 359r 3456 |
| 29 4 8 | 5 36 2r9g | 7 1 36 |
+----------------+----------------+-----------------+
| 1238 12389 149 | 3469 3569 4589 | 2345 7 23458 |
| 6 238 7 | 1 345 458 | 9 35 23458 |
| 38 5 49 | 349 2 7 | 1 6 348 |
+----------------+----------------+-----------------+
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if red is true, r2c5 must be 5 (r4c5=9)
if green is true, r2c8 must be 8 (r3c8=9)
either way, r2c8<>5
which makes r2c5=8 and r2c8=5 and the puzzle can be solved with nothing more elaborate than (lots of) multi-coloring and one or two xy-wings (not elaborate, har har). Again, watch out for those "9"s and "4"s and the occasional "3".
Exhausted .... |
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