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 Post subject: Question about a tesuji-problem
Post #1 Posted: Sat Jun 27, 2015 3:00 pm 
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In Lee Changho's Selected Tesuji Problems, I've encountered a tesuji-problem which, I think, has two solutions (a and b):


Black to play
Click Here To Show Diagram Code
[go]$$
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . , . . . . . , |
$$ | . X X O . . . . . . |
$$ | . O X O . . . . . . |
$$ | a . O X O . . . . . |
$$ | . O O X O . . . . . |
$$ | b O X X O . . . . . |
$$ | X O X , O . . . . , |
$$ | . X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ | . . . . . . . . . . |
$$ ---------------------[/go]


'a' was the solution given in the book, and I agree with that, but I think 'b' is also the right move.

My question is whether this problem has two solutions or not.

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 Post subject: Re: Question about a tesuji-problem
Post #2 Posted: Sat Jun 27, 2015 6:40 pm 
Gosei
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My two cents, in a relatively bad currency:

'b' is, in isolation just worse than 'a' if black later decides to sacrifice.

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 Post subject: Re: Question about a tesuji-problem
Post #3 Posted: Sun Jun 28, 2015 7:02 am 
Oza
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BadukStone wrote:
In Lee Changho's Selected Tesuji Problems, I've encountered a tesuji-problem which, I think, has two solutions (a and b):


Black to play
Click Here To Show Diagram Code
[go]$$
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . , . . . . . , |
$$ | . X X O . . . . . . |
$$ | . O X O . . . . . . |
$$ | a . O X O . . . . . |
$$ | . O O X O . . . . . |
$$ | b O X X O . . . . . |
$$ | X O X , O . . . . , |
$$ | . X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ | . . . . . . . . . . |
$$ ---------------------[/go]


'a' was the solution given in the book, and I agree with that, but I think 'b' is also the right move.

My question is whether this problem has two solutions or not.

It appears to have at least 3. :)

Interestingly, the Web Go Board extension that I use took your original asymmetrical 10x11 diagram and turned it into a 10x10 (a previously undiscoverd bug?), changing the problem to the situation below. This appears to have only one solution. What is it?
:study:
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | . X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | a . O X O . . . . . |
$$ | . O O X O . . . . . |
$$ | b O X X O . , . . . |
$$ | X O X . O . . . . . |
$$ | . X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ ---------------------[/go]

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 Post subject: Re: Question about a tesuji-problem
Post #4 Posted: Sun Jun 28, 2015 7:11 am 
Oza
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Great catch, Dave!

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 Post subject: Re: Question about a tesuji-problem
Post #5 Posted: Sun Jun 28, 2015 8:48 am 
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Very good, Dave! Better problem than the book!

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 Post subject: Re: Question about a tesuji-problem
Post #6 Posted: Sun Jun 28, 2015 9:00 am 
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Loons wrote:
My two cents, in a relatively bad currency:

'b' is, in isolation just worse than 'a' if black later decides to sacrifice.


Thanks, that makes sense now that I think about it. :scratch:

ez4u wrote:
This appears to have only one solution. What is it?
:study:


I think :b1: (b) is wrong this time, because the throw-in at :w2: works now:

( :b5: at :w2: )
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | . X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | . . O X O . . . . . |
$$ | 4 O O X O . . . . . |
$$ | 1 O X X O . , . . . |
$$ | X O X 6 O . . . . . |
$$ | 2 X X O . . . . . . |
$$ | 3 . O O . . . . . . |
$$ ---------------------[/go]

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 Post subject: Re: Question about a tesuji-problem
Post #7 Posted: Sun Jun 28, 2015 9:32 am 
Oza
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BadukStone wrote:
Loons wrote:
My two cents, in a relatively bad currency:

'b' is, in isolation just worse than 'a' if black later decides to sacrifice.


Thanks, that makes sense now that I think about it. :scratch:

ez4u wrote:
This appears to have only one solution. What is it?
:study:


I think :b1: (b) is wrong this time, because the throw-in at :w2: works now:

( :b5: at :w2: )
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | . X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | . . O X O . . . . . |
$$ | 4 O O X O . . . . . |
$$ | 1 O X X O . , . . . |
$$ | X O X 6 O . . . . . |
$$ | 2 X X O . . . . . . |
$$ | 3 . O O . . . . . . |
$$ ---------------------[/go]

You are on the right track! So what is the right answer?

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 Post subject: Re: Question about a tesuji-problem
Post #8 Posted: Sun Jun 28, 2015 10:31 am 
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So I believe that :b1: must be at the same spot as in the book:

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

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 Post subject: Re: Question about a tesuji-problem
Post #9 Posted: Sun Jun 28, 2015 12:49 pm 
Gosei
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Click Here To Show Diagram Code
[go]$$Bc Same problem as before?
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | . X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | 1 . O X O . . . . . |
$$ | . O O X O . . . . . |
$$ | . O X X O . , . . . |
$$ | X O X . O . . . . . |
$$ | 2 X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ ---------------------[/go]


Click Here To Show Diagram Code
[go]$$Bc Increasing liberties
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | 5 X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | 2 . O X O . . . . . |
$$ | 4 O O X O . . . . . |
$$ | 3 O X X O . , . . . |
$$ | X O X . O . . . . . |
$$ | 1 X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ ---------------------[/go]

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 Post subject: Re: Question about a tesuji-problem
Post #10 Posted: Sun Jun 28, 2015 1:36 pm 
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SoDesuNe wrote:
Click Here To Show Diagram Code
[go]$$Bc Same problem as before?
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | . X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | 1 . O X O . . . . . |
$$ | . O O X O . . . . . |
$$ | . O X X O . , . . . |
$$ | X O X . O . . . . . |
$$ | 2 X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ ---------------------[/go]

Click Here To Show Diagram Code
[go]$$Bc Increasing liberties
$$ ---------------------
$$ | . . X . . . . . . . |
$$ | . . . . . . . . . . |
$$ | 5 X X O . . . . . . |
$$ | . O X O . . , . . . |
$$ | 2 . O X O . . . . . |
$$ | 4 O O X O . . . . . |
$$ | 3 O X X O . , . . . |
$$ | X O X . O . . . . . |
$$ | 1 X X O . . . . . . |
$$ | . . O O . . . . . . |
$$ ---------------------[/go]

You're right, I overlooked this variation. :-?

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

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