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Capturing Race Exercise 7 Solution
    Keywords: Problem

[Diagram]
Black first

This isn't interesting I guess...


[Diagram]
White first

White 1 is the tesuji to delay Black's approach move at a. After White 3, having a shortage of liberties, Black is unable to play at a.


[Diagram]
White first.

If Black captures with 4, White 5 wins the capturing race by one move.


Bonus question: How many liberties (approach moves) does White have?

If Black plays first, White has 1 liberty left.

If White plays first, she threatens to capture 2 stones and live, gaining an infinite number of liberties, so Black must reply. Now White has 3 liberties.

As a combinatorial game?, White's liberties look like this:

     { -1 || -3 | -infinity }

(As with scores, we use negative numbers for White values.)

This is not a number, it is a game. White has a 2 liberty sente, with a liberty count of -3. Black's reverse sente gains 2 liberties instead of the usual 1.



This is a copy of the living page "Capturing Race Exercise 7 Solution" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.