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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Mon Apr 19, 2010 12:52 pm Post subject: Puzzle 10/04/19 (A) |
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| Code: | +-----------------------+
| 9 . 5 | . . . | 1 . 4 |
| . 7 . | . 4 . | . 9 . |
| 1 . . | 5 . 9 | 3 . . |
|-------+-------+-------|
| . . 1 | . . . | . . 3 |
| . 3 . | . 5 . | . 4 . |
| . . 4 | . . 8 | . 7 . |
|-------+-------+-------|
| 4 . 9 | . . . | 8 . . |
| . 2 . | . 9 5 | . . . |
| 3 . . | 2 . . | . . . |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Tue Apr 20, 2010 5:18 pm Post subject: |
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I went chain hunting but started with the kite...
| Quote: | kite(8); r4c8<>8
(5=2)r6c7-(2=6)r2c7-r2c1=r1c2-(6=9)r6c2-(9=8)r4c2-(8=5)r4c1; r6c1<>5 |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Apr 20, 2010 6:02 pm Post subject: |
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Well, I am not sure what my objective was but I ended up with a BBDBer; seven moves including a couple of unusual ones.
xy-wing 2-68
ALS 258 in r27c9
w-wing 15
Type 1 UR15 in r79c28 forces r7c8=3,
kite 8
x-wing 6
Kraken xyz-wing 269
Ted |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Tue Apr 20, 2010 7:16 pm Post subject: |
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Quite the most horrible 2 stepper I have ever done - hope Ted or one of you other guys puts me out of my misery: [edit Ah - I see you did !] Nice kite Peter
| Quote: | It was all about the 8s.
1. An x-chain on 8s sets up a contradiction: if r5c9 is set to "not 8" then if you follow the strong links on 8 via r4c8 and r4c2,r1c2, r3c3, r3c8 you will find r2c9 is also "not 8" which is a contradiction and so r5c9 must be 8.
(diagram to follow)
2. A horrid loop
(8=9)r4c2-(9=5)r4c7-(5=2)r6c7-(2=6)r4c8-(6=28)r13c8-(2=6)r2c7-(6=28)[r2c1|r3c3]-(8)r1c2 so r1c2 <>8 |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Apr 20, 2010 9:08 pm Post subject: |
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Although peterj's Kite was important to get past a bottleneck, only 2x X-Wing and a BUG+1 are needed to complete the puzzle.
BTW: This puzzle needs several basic steps beyond Singles. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Apr 21, 2010 3:42 am Post subject: |
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| Quote: | | Well, I am not sure what my objective was but I ended up with a BBDBer; |
I ended up with a (BBDB)², using a dozen steps, but I'm happy, I didn't think I'd solve it. |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Wed Apr 21, 2010 7:15 am Post subject: |
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| daj95376 wrote: | Although peterj's Kite was important to get past a bottleneck, only 2x X-Wing and a BUG+1 are needed to complete the puzzle.
BTW: This puzzle needs several basic steps beyond Singles. |
That would have saved me some considerable pain....... |
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oaxen
Joined: 10 Jul 2006
Posts: 96
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| Posted: Wed Apr 21, 2010 3:17 pm Post subject: |
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[quote="peterj"]I went chain hunting but started with the kite...
There are at least 4 bivalues where one can start for a one stepper solution |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Wed Apr 21, 2010 8:42 pm Post subject: |
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Yes..yes....more power to your algorithm Lars!  |
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oaxen
Joined: 10 Jul 2006
Posts: 96
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| Posted: Thu Apr 22, 2010 3:02 pm Post subject: |
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| Mogulmeister wrote: | | Yes..yes....more power to your algorithm Lars! |
Hello Mogulmeister.
Sometimes I think you suspect me to use some computerprogram for my chainsolving method. Of cource it is not so. Only paper and pencil.
Lars |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Thu Apr 22, 2010 5:11 pm Post subject: |
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Hi Lars - no that is not the reason. 
Your gnomic mantra "There are nn one steppers from the nn bivalues" is not especially illuminating by itself.
It is a bit like Fermat who wrote in the margin of his Arithmetica:
I have discovered a truly marvelous proof that it is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second into two like powers. This margin is too narrow to contain it. |
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oaxen
Joined: 10 Jul 2006
Posts: 96
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| Posted: Fri Apr 23, 2010 10:20 am Post subject: |
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[quote="Mogulmeister"]Hi Lars - no that is not the reason.
Your gnomic mantra "There are nn one steppers from the nn bivalues" is not especially illuminating by itself.
Sorry for repeating myself. The reason is I like the real tough puzzles where it is impossible to find a one-steper solution. And, heureka, sometimes Dan makes them very difficult, which makes me happy
Lars |
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