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Is this L&D solution right?
http://www.lifein19x19.com/viewtopic.php?f=11&t=10887		 Page 1 of 1
Author:  Matheus [ Wed Oct 01, 2014 10:24 am ]
Post subject:  Is this L&D solution right?
Hello everyone. In a L&D problem appearing in the app "Tsumego Pro" of Android the following position is presented (black to play):

Click Here To Show Diagram Code
[go]$$c Initial Position.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X X . . . . . . . . . . . . . . |
$$ | . O O O . X . . . . . . . . . . . . . |
$$ | O X X , . X . . . , . . . . . , . . . |
$$ | . . O O . X . . . . . . . . . . . . . |
$$ | O . O X . X . . . . . . . . . . . . . |
$$ | X O O X . X . . . . . . . . . . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


I have played :b1: and the app answered with :w2: and regarded my answer wrong. I think that the black stones inside form a "dead shape" which yields only one eye. Is there any way to white answer :b1: and make two eyes?

Click Here To Show Diagram Code
[go]$$c Proposed Solution.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X X . . . . . . . . . . . . . . |
$$ | . O O O . X . . . . . . . . . . . . . |
$$ | O X X 2 . X . . . , . . . . . , . . . |
$$ | . 1 O O . X . . . . . . . . . . . . . |
$$ | O . O X . X . . . . . . . . . . . . . |
$$ | X O O X . X . . . . . . . . . . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  Uberdude [ Wed Oct 01, 2014 10:44 am ]
Post subject:  Re: Is this L&D solution right?
That's not a dead shape but a seki. If you try to capture white you give him an alive shape. Note that even if black connects at a12 white can pass as he doesn't need to fill in at b14. (But if black a18 white needs to defend at a17.)
Author:  skydyr [ Wed Oct 01, 2014 10:46 am ]
Post subject:  Re: Is this L&D solution right?
White doesn't need to play on the inside in your diagram, because black can't keep his stones as a dead shape with another move. This means that black can never capture white. White can't play inside to capture black, as you noted, so your position is seki unless white can make an eye elsewhere, in which case he's just alive. For the purposes of tsumego, seki is alive, though generally less preferable than outright life.
Author:  Bill Spight [ Wed Oct 01, 2014 10:59 am ]
Post subject:  Re: Is this L&D solution right?
skydyr wrote:
For the purposes of tsumego, seki is alive, though generally less preferable than outright life.


That's also true for actual go. ;)
Author:  DrStraw [ Wed Oct 01, 2014 11:14 am ]
Post subject:  Re: Is this L&D solution right?
Once W gets the stone at :w2: there is no way to avoid a seki. Try to read out what happens if you appply the proverb "my opponent's vital point is my vital point." You will find that black can kill after all.

Click Here To Show Diagram Code
[go]$$c Initial Position.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X X . . . . . . . . . . . . . . |
$$ | . O O O . X . . . . . . . . . . . . . |
$$ | O X X 2 . X . . . , . . . . . , . . . |
$$ | . 1 O O . X . . . . . . . . . . . . . |
$$ | O . O X . X . . . . . . . . . . . . . |
$$ | X O O X . X . . . . . . . . . . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Author:  skydyr [ Wed Oct 01, 2014 11:29 am ]
Post subject:  Re: Is this L&D solution right?
Bill Spight wrote:
skydyr wrote:
For the purposes of tsumego, seki is alive, though generally less preferable than outright life.


That's also true for actual go. ;)


Of course. But people often distinguish the two rather than treat one as a subgroup of the other.
Author:  Matheus [ Thu Oct 02, 2014 10:14 am ]
Post subject:  Re: Is this L&D solution right?
That's enlightening! I had not considered the seki.
Thank you all for the help. :tmbup:
Author:  DrStraw [ Thu Oct 02, 2014 11:28 am ]
Post subject:  Re: Is this L&D solution right?
As no one seems to have taken up the challenge, here is the solution.

Click Here To Show Diagram Code
[go]$$c Initial Position.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X X X X . . . . . . . . . . . . . . |
$$ | . O O O 5 X . . . . . . . . . . . . . |
$$ | O X X 1 2 X . . . , . . . . . , . . . |
$$ | 6 3 O O 7 X . . . . . . . . . . . . . |
$$ | O 4 O X . X . . . . . . . . . . . . . |
$$ | X O O X . X . . . . . . . . . . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$c Initial Position.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | 7 X X X X . . . . . . . . . . . . . . |
$$ | 6 O O O 5 X . . . . . . . . . . . . . |
$$ | O X X 1 2 X . . . , . . . . . , . . . |
$$ | . 3 O O 4 X . . . . . . . . . . . . . |
$$ | O . O X . X . . . . . . . . . . . . . |
$$ | X O O X . X . . . . . . . . . . . . . |
$$ | . X X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
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