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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Sun Oct 26, 2008 4:58 am Post subject: October 26 VH |
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A not untypical puzzle.
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sun Oct 26, 2008 1:08 pm Post subject: Re: October 26 VH |
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| Marty R. wrote: | A not untypical puzzle.
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Right. My feeling exactly.
A tad too fast at the beginning. I was afraid it might all be over in 10 minutes ... (  ), and scanning for xy-wings yielded the one Marty found and solved the puzzle.
I'll go over it again later today to see what can be done without the xy-wing. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sun Oct 26, 2008 1:39 pm Post subject: |
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Now, that wasn't so bad after all ...
Done with basics, and eschewing the xy-.wing AND the UR (a type 3 /w SL on <4>), there is a Voldemort, whatever, here:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 379 237 -14 | 149* 6 479 | 8 5 123 |
| 569 26 18* | 3 58 59 | 7 4 12 |
| 357 37 148# | 148# 2 457 | 6 9 13 |
+--------------------------+--------------------------+--------------------------+
| 38 5 9 | 78 378 2 | 4 1 6 |
| 2 48 7 | 6 48 1 | 9 3 5 |
| 1 34 6 | 49 345 459 | 2 7 8 |
+--------------------------+--------------------------+--------------------------+
| 478 9 3 | 247 1 6 | 5 28 47 |
| 467 1 5 | 247 47 8 | 3 26 9 |
| 4678 678 2 | 5 9 3 | 1 68 47 |
+--------------------------+--------------------------+--------------------------+
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The "1"s in r1c4 and r2c3 form a pair of pincers to take out 1 from r1c3 (using sl<8> in row 3):
if r2c3<>1 then r3c3<>8 then r3c4=8 then r1c4=1; this means either r1c4 or r2c3 or both must be 1
Now, with r1c3=4, there is another you-know-what here:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 379 237 4 | 19 6 79 | 8 5 123 |
| 569 26 18 | 3 58 59 | 7 4 12 |
| 357 37 18 | 148# 2 457* | 6 9 13 |
+--------------------------+--------------------------+--------------------------+
| 38 5 9 | 78# 378 2 | 4 1 6 |
| 2 48 7 | 6 48* 1 | 9 3 5 |
| 1 34 6 | 49 345 -459 | 2 7 8 |
+--------------------------+--------------------------+--------------------------+
| 478 9 3 | 247 1 6 | 5 28 47 |
| 467 1 5 | 247 47 8 | 3 26 9 |
| 4678 678 2 | 5 9 3 | 1 68 47 |
+--------------------------+--------------------------+--------------------------+
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Again, it is a strong link on <8> that makes it all possible, this time in col 4:
if r5c5<>4 then r3c4=8 then r3c6=4, this means r6c6<>4
After cleanup, we get to this UR <4> (type 1) position
| Code: |
+--------------------------+--------------------------+--------------------------+
| 39 23 4 | 19 6 7 | 8 5 12 |
| 69 26 18 | 3 58 59 | 7 4 12 |
| 5 7 18 | 18 2 4 | 6 9 3 |
+--------------------------+--------------------------+--------------------------+
| 38 5 9 | 78 378 2 | 4 1 6 |
| 2 48 7 | 6 48 1 | 9 3 5 |
| 1 34 6 | 49 345 59 | 2 7 8 |
+--------------------------+--------------------------+--------------------------+
| 47+8 9 3 | 247 1 6 | 5 28 47 |
| 467 1 5 | 247 47 8 | 3 26 9 |
| 47 68 2 | 5 9 3 | 1 68 47 |
+--------------------------+--------------------------+--------------------------+
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and with r7c1=8 the puzzle is solved.
___
P.S. Caution. Advanced techniques used. Don't try this at home. 
____
edit 14:43 GMT+1 (no more daylight savings time) to make up for any headaches I might have caused, here's the recipe that made me do it (again, don't try this if you are not (supposed to be) drinking ethanol):
Frozen Lychee Margarita:
- open a can of Lychees. Pour the juice into an ice cube tray and freeze. Keep the fruits
- When well frozen, take two or three Lychee cubes (about 2 oz. each) and 3 more regular ice cubes and put them into a blender together with the juice from 1 lime, 2 oz. Silver Tequila and 1 oz Lychee Liqueur. Blend until smooth and pour into a suitable glass. Add one or two whole Lychees. Solve another Sudoku  |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Oct 26, 2008 2:41 pm Post subject: |
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Nataraj is a hard act to follow, especially if you used the xy-wing to solve this "not untypical" sudoku.
I went to an affair last night and towards the end, various "blends" were being offered. Gratefully, no actual recipe existed to offer to this group since the drinks were really bad!
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Oct 26, 2008 3:53 pm Post subject: |
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| Quote: | The "1"s in r1c4 and r2c3 form a pair of pincers to take out 1 from r1c3 (using sl<8> in row 3):
if r2c3<>1 then r3c3<>8 then r3c4=8 then r1c4=1; this means either r1c4 or r2c3 or both must be 1 |
That's very good, I'm impressed. The reasoning is easy, but what did you see there to make you stop and examine further? |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sun Oct 26, 2008 5:12 pm Post subject: |
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| Marty R. wrote: | | The reasoning is easy, but what did you see there to make you stop and examine further? |
This diagram made me stop and examine further (red and green annotations added afterwards):
The 1 in r2c3 (representing the bi-value cell <1,8>) and the line r3c3=r3c4 (representing the strong link in 8 ), both circled in green, are the first clue.
Some clues lead to eliminations, some don't (like the other numbers circled in red: they all see strong links, but none of them is useful-yet) |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sun Oct 26, 2008 8:15 pm Post subject: |
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| I guess I thought I'd finished without using anything 'very hard'. Not the first time in my life. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Oct 26, 2008 9:39 pm Post subject: |
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| Thank you. |
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