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Offline unkx80
 Post subject: Classical problem
Post #1 Posted: Sun Feb 20, 2011 1:29 am 
Lives with ko

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For those interested, here is a classical problem. For those who have not seen it before, it may be harder than its appearance.

Click Here To Show Diagram Code
[go]$$B Black to play
$$ -----------------------
$$ . . . . . . . . . O . .
$$ . . . . . O . . . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]

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This post by unkx80 was liked by: Dusk Eagle
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Offline tj86430
 Post subject: Re: Classical problem
Post #2 Posted: Sun Feb 20, 2011 1:55 am 
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Naturally my first instinct is:

Click Here To Show Diagram Code
[go]$$B Black to play
$$ -----------------------
$$ . . . . . . . . . O . .
$$ . . . . . O . B . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


and I can't see how white would survive, but since this is supposed to be hard I guess it's wrong.

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Offline daniel_the_smith
 Post subject: Re: Classical problem
Post #3 Posted: Sun Feb 20, 2011 3:15 am 
Gosei
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@tj:

Click Here To Show Diagram Code
[go]$$W Black to play
$$ -----------------------
$$ . . . . . . . 1 . O . .
$$ . . . . . O 3 B 2 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$W Black to play
$$ -----------------------
$$ . . . . . . . 1 . O . .
$$ . . . . . O 2 B 3 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]



I was about to post a solution but mine was wrong too... >.<

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Offline Jordus
 Post subject: Re: Classical problem
Post #4 Posted: Sun Feb 20, 2011 3:25 am 
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@Daniel Smith

i think :b2: defeats your :w1: ...

Click Here To Show Diagram Code
[go]$$W Black to play
$$ -----------------------
$$ . . . . . 5 2 1 3 O . .
$$ . . . . 6 O 4 B . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


only 1 eye if white captures blacks 3 stones because black will play @ 4.

Click Here To Show Diagram Code
[go]$$W :b6: @ 1 :b8: @1
$$ -----------------------
$$ . . . . . 7 2 1 4 O . .
$$ . . . . . O 3 B 5 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]

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Offline Sverre
 Post subject: Re: Classical problem
Post #5 Posted: Sun Feb 20, 2011 3:26 am 
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unkx80 wrote:
For those interested, here is a classical problem. For those who have not seen it before, it may be harder than its appearance.


Click Here To Show Diagram Code
[go]$$B I think ko is best.
$$ -----------------------
$$ . . . . . . 3 2 . O . .
$$ . . . . . O . 1 4 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$B If W gets the comb formation he lives, so we need a placement.
$$ -----------------------
$$ . . . . . 2 . . . O . .
$$ . . . . 1 O . . . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$B This looks tempting, but the liberty at a is inconvenient.
$$ -----------------------
$$ . . . . . . 2 1 . O . .
$$ . . . . 4 O . 3 . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X a X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$B And the other placement seems to force a ko.
$$ -----------------------
$$ . . . . . . 3 2 . O . .
$$ . . . . . O . 1 4 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$B Playing something like :b1: still ends up in ko.
$$ -----------------------
$$ . . . . . . 1 2 . O . .
$$ . . . . . O . 3 4 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


EDIT:
Forgot this variation, if I missed something it's probably somehow related to this :b1:.
Click Here To Show Diagram Code
[go]$$B The Black attachment is tricky, is this right?
$$ -----------------------
$$ . . . . 6 1 5 3 . O 7 .
$$ . . . . 2 O 8 4 . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


Last edited by Sverre on Sun Feb 20, 2011 3:36 am, edited 1 time in total.
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Offline tj86430
 Post subject: Re: Classical problem
Post #6 Posted: Sun Feb 20, 2011 3:35 am 
Gosei

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Jordus wrote:
@Daniel Smith

i think :b2: defeats your :w1: ...

Click Here To Show Diagram Code
[go]$$W Black to play
$$ -----------------------
$$ . . . . . 5 2 1 3 O . .
$$ . . . . 6 O 4 B . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]


only 1 eye if white captures blacks 3 stones because black will play @ 4.

Click Here To Show Diagram Code
[go]$$W :b6: @ 1 :b8: @1
$$ -----------------------
$$ . . . . . 7 2 1 4 O . .
$$ . . . . . O 3 B 5 O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]

This is what I had in mind

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Offline daniel_the_smith
 Post subject: Re: Classical problem
Post #7 Posted: Sun Feb 20, 2011 4:12 am 
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:oops:

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Offline explo
 Post subject: Re: Classical problem
Post #8 Posted: Sun Feb 20, 2011 4:59 am 
Dies with sente

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@ Jordus, Daniel and tj86430

3 should be at 5 in the second diagram, and white gets a ko. Black can do better than that.



Click Here To Show Diagram Code
[go]$$B Black to play
$$ -----------------------
$$ . . . 8 5 . 2 1 . O . .
$$ . . 7 6 4 O 9 3 . O X .
$$ . X . X X X O O O X X .
$$ . . . . . . X . X . . .
$$ . . . . . . . X . . . .
$$ . . . . . . . . . . . .[/go]

This post by explo was liked by: Sverre
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Offline unkx80
 Post subject: Re: Classical problem
Post #9 Posted: Sun Feb 20, 2011 2:00 pm 
Lives with ko

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Yes, explo got it.
Solution is unconditional death by bulky five.

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