OD1P - May 22 Problem / Solution

Black To Play  

.. a at ^[1]

...b at ^[2]

...c at ^[3]

...d at ^[4]

...e at ^[5]

...f at ^[6] (Correct solution)

Black fails  

White connects, main black group is dead even if the three stones on left might escape.

Black plays at Q18  

Q18, Black dies in failure.

Black Start  

Black lives only if White plays this sequence follishly to allowing Blace to capture at a. White can play b as , , , or even to connect to White's two stones and thus kill the main Black group even if allowing Black's few stones on left to escape if they can. The longer White delays in playing b after , the better for Black.

Black Start  

signal9: I'm not 100% sure, but this looks pretty good to me.

Black Start  

unkx80: Nah... this is a failure diagram.

Order?  

YongCao? I think should play first, then .

Black Dies  

PeiweiCao? Black dies:

Black plays at O19  

Correct Solution

Black Start  

PeiweiCao? Now White has two choices:

Gregory at a or b. After either choice White must next choose whether to capture Black's two stones in the corner or four stones on the left leaving the other group to make the second eye for Black. In all scenarios, it seems to me that White will be better off after to capture it and the two supporting stones and to allow Black to live have the second eye in the corner. This makes the White wall on the left solid with no cutting points.

White Choice 1  

Black lives.

Gregory After White can play either at or (in which case letting Black play at ).

Or...

White Choice 2  

PeiweiCao? One of the two blocks of White will be eaten, and Black lives.

White Choice 2 (Continued)  

Jared: This could be called a "double sacrifice" set-up, with a "double-snapback-threat throw in"

PeiweiCao?: Consider white move 2 at p19 instead of m18, I believe that white p19 assures the death of the black corner.

Black Start  

unkx80: If , then the tesuji of and should ensure life.

Black Start  

Alexandros? Not a very good player here, but I think PeiweiCao?'s method fails to the following:

B Black Start  

Then, as I read it, if black picks this path: (with move 3 filling in the liberty)

Black Start  

unkx80: at ?

Gregory Yes, If Black plays at (of the previous diagram) then White has to choose between a and b to decide which group to capture and which to let live to make the second eye. The capture at a seems the obvious choice.

Black Start  

Alexandros?: I'm not sure if it's cheating in a problem, but White could play at in that case, and run into the wall at the other end of the board. Of course, this goes beyond the bounds given for the problem, so it may be wrong...

unkx80: By the usual conventions in life-and-death, we assume that the rest of the board is empty, so feel free to extend the diagram as you wish, so this is not cheating.

For your question of at , I leave it as an exercise: What is the gist of this problem? The tesuji has been mentioned on this page at least twice already...

Gregory If White plays at (of previouse diagram) then Black plays at P18 for double atari to capture the two White stones when White saves the three stones in the corner. However since Black is open on the top this is not so good for White.

Black Death?  

Boardwalk?: Doesn't kill black. Allowing for the run to the other edge of course.

unkx80: is a mistake, should be at .

Correct Solution  

BluPian0: A tricky snapback to find. Thanks goes to Violence for helping me find the solution.

While closes at top.  

Gregory In this variation on the solution of at O19, after , White takes in corner with leaving atari on the four Black stones forcing , so White can close the top with if needed.

Correct Solution?  

AVAVT: Hm... I doubt this is the proper solution. After what would you do?

Correct Solution?  

AVAVT: Oh Black can still live. I didn't notice .