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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Fri Feb 08, 2008 7:58 am Post subject: Friday Feb 8 nightmare |
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Today's nightmare http://www.sudocue.net/daily.php really deserves that name. After coloring (4,8 and some more 8s) gives a few eliminations, this is the end of the line for me:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 3679 179 5 | 12369 8 123679 | 4 239 2379 |
| 3679 79 68 | 2369 5 4 | 237 1 23789 |
| 34789 1479 2 | 139 17 1379 | 378 6 5 |
+--------------------------+--------------------------+--------------------------+
| 1 247 47 | 23 6 8 | 5 2349 2349 |
| 46 3 68 | 125 9 125 | 12 7 48 |
| 28 5 9 | 4 127 1237 | 1238 238 6 |
+--------------------------+--------------------------+--------------------------+
| 5 6 47 | 8 12 12 | 9 34 37 |
| 249 8 1 | 7 3 569 | 26 245 24 |
| 279 279 3 | 569 4 569 | 2678 258 1 |
+--------------------------+--------------------------+--------------------------+ |
No useful DPs (at least I could not find any), so I resorted to Medusa one more time. I liked the strong links in 8, and also some in 4, so I chose {4,8} in r5c9 as starting point.
In this picture you can see the full Medusa, plus the three steps that got me going again:
First step: r3c1. If red, then it is 8, if green, then r5c1=4, either way, r3c1<>4.
This means that r3c2 solves to 4 and 4 in r8c1 becomes red (only 2 4s in col 1)
Second step (red branch): if red, then
- r5c9 = 4 then r8c9=2 and r8c8<>2 AND
- r8c1 = 4 then r8c8<>4 THEN
r8c8=5
Third step (green branch): if green, then
- r5c9=8 then r6c8<>8 then r9c8=8 THEN
r8c8=5
sooo
=> either way (red or green), r8c8=5 and r9c8=8 (if green, see green branch above, if red then not 2 because of r9c2)
Far from over, there are some wings on the way and again, a tight spot:
| Code: | +--------------------------+--------------------------+--------------------------+
| 3679 1 5 | 2369 8 23679 | 4 239 2379 |
| 3679 79 68 | 2369 5 4 | 237 1 23789 |
| 3789 4 2 | 139 17 1379 | 378 6 5 |
+--------------------------+--------------------------+--------------------------+
| 1 27 47 | 23 6 8 | 5 2349 39 |
| 46 3 68 | 125 9 125 | 12 7 48 |
| 28 5 9 | 4 127 1237 | 1238 23 6 |
+--------------------------+--------------------------+--------------------------+
| 5 6 47 | 8 12 12 | 9 34 37 |
| 249 8 1 | 7 3 69 | 26 5 24 |
| 279 279 3 | 569 4 569 | 267 8 1 |
+--------------------------+--------------------------+--------------------------+
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I did find some xy-chains, but ...
That was one loooooooooong nightmare! |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Fri Feb 08, 2008 10:24 pm Post subject: |
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nataraj,
Basic Medusa alone solves the puzzle from your "end of the road" point, and without using any "extended" techniques as you did to fix the <8>. (And this is me, the troublemaker who stirred up this whole "extended Medusa" thing saying this!)
Starting from the grid after eliminating the <4> in r3c1 and marking Medusa completely:
| Code: |
+-----------------+----------------+----------------------+
| 3679 1 5 | 2369 8 23679 | 4 239 2379 |
| 3679 79 6r8g | 2369 5 4 | 237 1 #23-78r9 |
| 378r9 4 2 | 139 17 1379 |#3-78g 6 5 |
+-----------------+----------------+----------------------+
| 1 2g7r 4r7g | 23 6 8 | 5 2349 2349 |
| 4g6r 3 6g8r | 125 9 125 | 12 7 4r8g |
| 2r8g 5 9 | 4 127 1237 | 1238 238 6 |
+-----------------+----------------+----------------------+
| 5 6 4g7r | 8 12 12 | 9 3g4r 3r7g |
| 24r9 8 1 | 7 3 569 | 26 245 24 |
| 279 2r79 3 | 569 4 569 |#267r-8 258 1 |
+-----------------+----------------+----------------------+
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There are 3 eliminations in the right tower, marked #. This leads to:
| Code: |
+------------------+----------------+----------------------+
| 3679 1 5 | 2369 8 23679 | 4 #2-39 237r9 |
| 3679 #-79 6r8g | 2369 5 4 |#2-37g 1 238r9 |
| 378r9 4 2 | 139 17 1379 | 3r8g 6 5 |
+------------------+----------------+----------------------+
| 1 2g7r 4r7g | 23 6 8 | 5 234g9 #-23-49 |
| 4g6r 3 6g8r | 125 9 125 | 12 7 4r8g |
| 2r8g 5 9 | 4 127 1237 | 1238r 23 6 |
+------------------+----------------+----------------------+
| 5 6 4g7r | 8 12 12 | 9 3g4r 3r7g |
| 24r9 8 1 | 7 3 69 | 26 5 2r4g |
| 279 2r79 3 | 569 4 569 | 267r 8 1 |
+------------------+----------------+----------------------+
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5 more eliminations, in 4 cells, again marked #. This solves the puzzle and was nothing but basic Medusa. |
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