XuanxuanQijingProblem98/Solution

 

=.

 

This is the best result for black: one-step ko for white and four-step ko for black.

 

If tries to make life for the black group, takes away both black eyes.

 

Another variation after . With white avoids the ko and wins the capturing race with 5 liberties vs. 3.

This last variation shouldn't exist. First, instead of at 1-1, to the left of instead kills black simply while leaving no black ko threats. However, white need not play locally at all; even if black got to play to the left of , white would take a liberty in the corner, and black would have no other move but throw a stone in at 1-1, which would create a three-move approach ko, practically meaning death for black.

I agreed, played at the left of is better than at 1-1. I have made the change. However, when providing a solution to a life-and-death problem, a result that avoids ko, no matter how many steps, is always preferable over ko. So I think a move does need to be played locally by white.