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Offline oren
 Post subject: Interesting go problem from Daiki Komatsu twitter
Post #1 Posted: Wed Nov 02, 2016 11:17 am 
Oza
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https://twitter.com/daiki__0417/status/ ... 0487126018

How many moves does white need to live inside?
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Offline Kirby
 Post subject: Re: Interesting go problem from Daiki Komatsu twitter
Post #2 Posted: Wed Nov 02, 2016 12:47 pm 
Honinbo

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Nice problem... One of the comments seems to suggest 7, but I don't see it, yet.

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Offline HermanHiddema
 Post subject: Re: Interesting go problem from Daiki Komatsu twitter
Post #3 Posted: Wed Nov 02, 2016 1:35 pm 
Gosei
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Copyable diagram, for those who want to post an attempt:
Click Here To Show Diagram Code
[go]$$ How many :white: to live?
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . . . X |
$$ . X . . . . . |
$$ . X . . . . . |
$$ . X . X . . . |
$$ . X X X X X X |
$$ . . . . . . . |[/go]


My solution:

Click Here To Show Diagram Code
[go]$$ 7 stones needed
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . O O X |
$$ . X . . . . O |
$$ . X . O . O . |
$$ . X . X . O O |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

This post by HermanHiddema was liked by: Kirby
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Offline Uberdude
 Post subject: Re: Interesting go problem from Daiki Komatsu twitter
Post #4 Posted: Wed Nov 02, 2016 2:33 pm 
Judan

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I was thinking it might be a bit of a trick question in that you can use fewer white moves by also adding black moves as below, but such shapes probably require too much connection. Could be a nice idea for composing another problem though.
Click Here To Show Diagram Code
[go]$$B
$$ . . . . . . .
$$ . . O O O O .
$$ . O . O . O .
$$ . O O O O . .
$$ . . . . . . .[/go]

vs
Click Here To Show Diagram Code
[go]$$B
$$ . . . . . . .
$$ . . O O O O .
$$ . O X . X O .
$$ . O O O O . .
$$ . . . . . . .[/go]
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Offline Cassandra
 Post subject: Re: Interesting go problem from Daiki Komatsu twitter
Post #5 Posted: Wed Nov 02, 2016 3:07 pm 
Lives in sente
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Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X O O O . X |
$$ . X O . O O . |
$$ . X . O . O . |
$$ . X . X O O . |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

The minimum size for a living group in the centre with "closed borders" is 10 stones.
>>> No chance to create an "open borders" shape with less stones.

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . O O X |
$$ . X . . O . O |
$$ . X . . O O . |
$$ . X . X . O O |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

The minimum size for a living group at the edge of the board with "closed borders" is 8 stones.

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . O O X |
$$ . X . . O . O |
$$ . X . . P O . |
$$ . X . X . O O |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

The marked white covers a potential cutting point.

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . O O X |
$$ . X . . O . O |
$$ . X . O . O . |
$$ . X . X . O O |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

No option left for Black to cut.

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . O O X |
$$ . X . . P . O |
$$ . X . O . O . |
$$ . X . X . O O |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

The marked stone is not necessary any longer.

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . |
$$ . X X X X X X |
$$ . X . . O O X |
$$ . X . . . . O |
$$ . X . O . O . |
$$ . X . X . O O |
$$ . X X X X X X |
$$ . . . . . . . |[/go]

>>> 7 stones

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Igo Hatsuyōron #120 (really solved by KataGo)
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