Life In 19x19

Hi, I'm a beginner and I installed an android app with go problems and solutions, one of the problems is


white has to capture black, and one of the solutions is


please explain why is this a solution?

Does not look like a solution - are you sure it is supposed to be one?

The first solution is a common net. After that move black cannot get out.

Click Here To Show Diagram Code

[go]$$W Black is in atari
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X C . . .
$$ | . X O X 4 5 . .
$$ | . O O 2 1 . . .
$$ | . . . 3 . . X .
$$ | . . . . X . . .
$$ | . . . . . . . .[/go]

As for the second solution, it doesn't seem to work. It may also be net, but looser and more complicated. As Kageyama teaches in Lessons in the Fundamentals of Go, if there are two options to capture your opponent's stones, always choose the firmer of the two. The first solution should always be played in this situation.

Black 2 seems to be the move to get out. Without the marked black stone it doesn't work because of something like the cross-cut tesuji. Since that black stone is there, however, it does. White 3 doesn't seem to do anything to prevent black from connecting and it doesn't. Black 4 connects back to the marked stone.

Click Here To Show Diagram Code

[go]$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X . . . .
$$ | . X O X 3 . . .
$$ | . O O 4 2 1 . .
$$ | . . . . . . X .
$$ | . . . . B . . .
$$ | . . . . . . . .[/go]

If the marked stone is not there here is how the solution works. If black cross-cuts white just captures the black cutting stones.

Click Here To Show Diagram Code

[go]$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X C . . .
$$ | . X O X 6 7 . .
$$ | . O O 5 2 1 . .
$$ | . . . . 3 4 X .
$$ | . . . . . . . .
$$ | . . . . . . . .[/go]

If black tries to force his way out, white still captures the cutting stones.

Click Here To Show Diagram Code

[go]$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X 6 7 . .
$$ | . X O X C . . .
$$ | . O O 4 2 1 . .
$$ | . . . 5 3 . X .
$$ | . . . . . . . .
$$ | . . . . . . . .[/go]

moyoaji wrote:As for the second solution, it doesn't seem to work. It may also be net, but looser and more complicated. As Kageyama teaches in Lessons in the Fundamentals of Go, if there are two options to capture your opponent's stones, always choose the firmer of the two. The first solution should always be played in this situation.

Black 2 seems to be the move to get out. Without the marked black stone it doesn't work because of something like the cross-cut tesuji. Since that black stone is there, however, it does. White 3 doesn't seem to do anything to prevent black from connecting and it doesn't. Black 4 connects back to the marked stone.

$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X . . . .
$$ | . X O X 3 . . .
$$ | . O O 4 2 1 . .
$$ | . . . . . . X .
$$ | . . . . B . . .
$$ | . . . . . . . .

Click Here To Show Diagram Code

[go]$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X . . . .
$$ | . X O X 3 . . .
$$ | . O O 4 2 1 . .
$$ | . . . . . . X .
$$ | . . . . B . . .
$$ | . . . . . . . .[/go]

but, doesn't work if white plays 3 at 4 instead?

Click Here To Show Diagram Code

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

I think is fine. Its 3 and 4 that are out of order.

edit: maybe I'm wrong. It does look more complicated to read.

xed_over wrote:but, doesn't work if white plays 3 at 4 instead?

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

Click Here To Show Diagram Code

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

I think is fine. Its 3 and 4 that are out of order.

edit: maybe I'm wrong. It does look more complicated to read.

I don't think it works. I tried that and this is what I came up with for black.

Click Here To Show Diagram Code

[go]$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X . . . .
$$ | . X O X 4 8 0 .
$$ | . O O 3 2 1 9 .
$$ | . . . 7 5 6 X .
$$ | . . . . B . . .
$$ | . . . . . . . .[/go]

Black is out.

EDIT: Bill's solution below is even better. Black is out and white is probably dead on both sides after those white stones die. However, the ladder must work for black.

Click Here To Show Diagram Code

[go]$$W
$$ ------------------
$$ | . . . . . . . .
$$ | . X X . . . . .
$$ | . . X O O . X .
$$ | . X O X . . . .
$$ | . X O X 4 8 . .
$$ | . O O 3 2 1 9 0
$$ | . . . 7 5 6 X .
$$ | . . . . B . . .
$$ | . . . . . . . .[/go]

I don't recognize that Android app. Which is it?

Drew wrote:I don't recognize that Android app. Which is it?

Hactar Go Lite

thanks everyone for the replies !

Hi,

Thank you for pointing out the error; wrong variation was mistakenly marked as correct in this problem.
Next update will correct this.

- Lauri