From: Colin Paul Adams <colin <at> COLINA <dot> DEMON <dot> CO <dot> UK>
Date: 4 feb 2000
Subject: CHU: A18 and A21

My program gives the following solution to A18:

1. Ln x 8e x 9d,  K - 11a
2. +DK x! 6a,     C - 6a
3. Ln x 10c x 9b, +VM x 9b
4. +DK x 6a,      +VM - 9a
5. DH x 10b+,     R x 10b
6. +DK x 9a,      K - 11b
7. +DK x 12a,     K - 11c
8. FK - 11a,      R - 11b
9. FK x 11b Mate in 17

This is the same length as the suggested Solution.
As for the sideline given in the published solution:

1. Ln - 9d, K - 11a
2. +DK - 7a

then what does Black do after K - 12b? The line suggested after
1. ..., K - 12b is no longer possible. My program says (definitively)
that there is no solution, so the published solution is not correct.

For A21, my program basically plays the same line as in the published
solution (mating one/two moves earlier, as is pointed out in a
comment), but with a slightly different defence. For the record:

1. +VM - 7b,  K x 7b
2. DH - 7d+,  K - 8b
3. +DH - 8d,  K - 7b
4. +L x 9d,   GB x 9d
5. +DH x 9d,  K - 8b
6. DK - 8i,   FK - 8g (this is where the defence differs - I presume
this is not significant)
7. DK x 8g,   K - 9a
8. +DH - 12a, BT - 10a
9. +DH - 12d, K - 9b
10. DK - 8c+ Mate in 19
--
Colin Paul Adams
Preston Lancashire