neal@rochester.UUCP (Neal Gafter) (01/30/86)
<atari, line eater>
Here is the answer to the problem sent Jan 29, and another "easy"
Tesuji problem.
=76=14=================================================
ANSWER
A B C D E F G H J K L M N O P Q R S T
10 + + + O + + + + + . + + + + + . + + + 10
9 + + + + + + + + + + + + + + + + + + + 9
8 + + + O + + + + + + + + + + + + + + + 8
7 + + + + + + + + + + + + + + + + + + + 7
6 + + O + + O X + + + + + + + + X + + + 6
5 + + + + + + + X + + + + + + + + + + + 5
4 + + + X O O O X + O + + + + + X + + + 4
3 + + + X X O X O O + + + + O + + + + + 3
2 + + + + + X X + + + + + + + + + + + + 2
1 + + + + + + + + + + + + + + + + + + + 1
A B C D E F G H J K L M N O P Q R S T
X's move. The four O stones (f4 and attached) can be captured by X. The
move for the task is X:e6. This move makes miai of f5 and f7, and the
four stones cannot escape. The probable sequence of moves locally will be:
X:e6 O:f7 X:f5
miai: a term describing two points on the board which have the property
that if one player moves on one of these points the other player will move
on the other.
For those wondering why O still can't escape, the continuation would be:
O:e5 (atari) X:d5 (atari) O:g5 (captures 1) X:f5 (captures 6)
This situation, in which by capturing a player puts some of his own
stones into atari, is called a snapback. It is a basic Tesuji to
sacrifice a stone to force this situation, as in this problem.
=123=12================================================
PROBLEM
A B C D E F G H J K L M N O P Q R S T
10 . . . + . . . . . + . . . . . + . . . 10
9 . . . . . . . . . . . . . . . . . . . 9
8 . O O . . . . . . . . . . . . . . . . 8
7 . X . . . . . . . . . . . . . . . . . 7
6 X O O . . . . . . . . . . . . . X . . 6
5 . X O O . . . . . . . . . . . . . . . 5
4 . X X O . . . . . + . . . O . O . . . 4
3 . . O X X X . . . X . . . . . . . . . 3
2 . . O . O X . . . . . . . . . . . . . 2
1 . . . . . . . . . . . . . . . . . . . 1
A B C D E F G H J K L M N O P Q R S T
X to move. There seems to be a fight in the lower left hand corner.
There is a pitfall here involving a ko which X must avoid. Can you see
the solution and also the pitfall?
ko: a repetetive situation in which by capturing a single stone, the
stone which is played is put into atari. There is a special rule
covering ko which says that the board position may never repeat,
so a move called a "ko threat" must be played before a recapture.
I will post the answer in about a week. Any responses should be sent to
me by mail.
--
Neal Gafter
Arpa: neal@Rochester.arpa
UUCP: ...{rocksvax|allegra|seismo|decvax}!rochester!neal
USnail: Department of Computer Science, U. of Rochester, N.Y. 14627
phone: (716) 275 - 2569 (office) or (716) 275 - 5377 (lab)