Life In 19x19

Can someone please help me to understand this solution?

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ . . . . . . . O . |
$$ . . . O O X O X X |
$$ . . . O X O 1 2 X |
$$ . . . O X 3 O O X |
$$ . . . O . X X X . |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

I guessing it should mean that the five white stones in surrounded by black are dead. But couldn't white still play Q19?

I thought it might turn out like this but not sure how probable this is:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ . . . . . 4 . O . |
$$ . . . O O . O X X |
$$ . . . O X O 6 2 X |
$$ . . . O X 3 O O X |
$$ . . . O . X X X 5 |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

Also, can someone tell me if this is supposed to be a common life and death shape?

Source

(Sorry I can't seem to get the coordinates to display on the right side of the board)

In your second diagram, Black should play at

libcat wrote:I guessing it should mean that the five white stones in surrounded by black are dead. But couldn't white still play Q19?

Big picture: the focus isn't on capturing a few white stones, it's on whether the black group can live. Capturing stones is just a means to an end.

Details: what jlt said :-)

libcat wrote:Also, can someone tell me if this is supposed to be a common life and death shape?

Not a common L&D shape as such. But the throw-in (sacrificing a black stone at R17) is a common technique, so stronger players would see the key move at a glance (and then maybe spend a few seconds reading to check that it works in this context).

Picture worth 100 words:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ . . . . . 4 . O . |
$$ . . . O O . O X X |
$$ . . . O X O 5 . X |
$$ . . . O X 3 . . X |
$$ . . . O . X X X . |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

xela wrote:Big picture: the focus isn't on capturing a few white stones, it's on whether the black group can live. Capturing stones is just a means to an end.

Worth repeating.

Just to add my 2¢.

libcat wrote:Can someone please help me to understand this solution?

$$Bc
$$ ------------------
$$ . . . . . . . O . |
$$ . . . O O X O X X |
$$ . . . O X O 1 2 X |
$$ . . . O X 3 O O X |
$$ . . . O . X X X . |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ . . . . . . . O . |
$$ . . . O O X O X X |
$$ . . . O X O 1 2 X |
$$ . . . O X 3 O O X |
$$ . . . O . X X X . |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

I guessing it should mean that the five white stones in surrounded by black are dead. But couldn't white still play Q19?

You are right that if connects at 1, Black could capture the resulting clump of 6 White stones. They would be more than dead. You are also right that should capture the single Black stone by playing at Q-19.

libcat wrote:I thought it might turn out like this but not sure how probable this is:

$$Wcm4
$$ ------------------
$$ . . . . . 1 . O . |
$$ . . . O O B O X X |
$$ . . . O X O 3 W X |
$$ . . . O X B W W X |
$$ . . . O . X X X 2 |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$Wcm4
$$ ------------------
$$ . . . . . 1 . O . |
$$ . . . O O B O X X |
$$ . . . O X O 3 W X |
$$ . . . O X B W W X |
$$ . . . O . X X X 2 |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

(Diagram edited by me.)

If Black fills at , it is possible that White will save his stones by filling at . should capture the stones by playing at 6. In fact, capturing the White stones was the point of the original throw-in.

BTW, life and death problems often occur in restricted spaces, because with enough space it is usually easy to live. Typically, but not always, they will involve a potential 1 pt. eye, because that's the smallest eye you can make, and space is at a premium. In this problem, where is Black's potential one point eye? At 5. It is typically important for Black not to fill that eye. (!)

Click Here To Show Diagram Code

[go]$$Wcm4 Black is dead
$$ ------------------
$$ . . . . . W . O . |
$$ . . . O O . O X X |
$$ . . . O X O . W X |
$$ . . . O X B W W X |
$$ . . . O . X X X 2 |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

In fact, after fills the potential one point eye, the Black group is dead as it lies, given alternating local play. Even if Black captures the three White stones that are in atari, White can kill, as you may verify.

Woah, this forum is great!

@JLT / Xela / Uberdude
Thanks - I was staring at the screen for ages and still couldn't see it.
Okay I'm going check out 'throw-ins'.

Bill Spight wrote: BTW, life and death problems often occur in restricted spaces, because with enough space it is usually easy to live. Typically, but not always, they will involve a potential 1 pt. eye, because that's the smallest eye you can make, and space is at a premium. In this problem, where is Black's potential one point eye? At 5. It is typically important for Black not to fill that eye. (!)

$$Wcm4 Black is dead
$$ ------------------
$$ . . . . . W . O . |
$$ . . . O O . O X X |
$$ . . . O X O . W X |
$$ . . . O X B B W X |
$$ . . . O . X X X 2 |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$Wcm4 Black is dead
$$ ------------------
$$ . . . . . W . O . |
$$ . . . O O . O X X |
$$ . . . O X O . W X |
$$ . . . O X B B W X |
$$ . . . O . X X X 2 |
$$ . . . . O . . X X |
$$ . . . . . O . O . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |[/go]

In fact, after fills the potential one point eye, the Black group is dead as it lies, given alternating local play. Even if Black captures the three White stones that are in atari, White can kill, as you may verify.

Thanks for the explanation, it's helped to convince me that I was a bit daft to put Black at :/

In fact, for most of the time when trying to solve this, I actually completely forgot about the 1 pt eye that you mentioned!

I look forward to getting more smiley-filled help posts from you in the future

libcat wrote:Woah, this forum is great!

Totally agree. Keep on posting interesting questions for us :-)