No. of units | A | B | C | D | E | F | |
2 | |||||||
3 | 1 | 1 | |||||
4 | 2 | 3 | 1 | ||||
5 | 3 | 2 | |||||
6 | 4 | 3 | |||||
7 | 1 | 6 | |||||
8 | 2 | 5(Cx) | 7 | 1 | |||
9 | 7 | ||||||
10 | 8 | 2 | |||||
11 | 3 | 8(C) | 9 | ||||
12 | 5 | ||||||
13 | |||||||
14 | 6 | 10(C) | 11 | ||||
15 | 1 | ||||||
16 | 11(C) | 12 | |||||
17 | 3 | ||||||
18 | 16 | 16(A) | 16(A) | ||||
19 | |||||||
20 | |||||||
21 | |||||||
22 | 15 | ||||||
23 | 24 | ||||||
24 | 20 | 20(A) | 29 | 11 | |||
25 | 28 | 28(A,Cx) | 37 | ||||
26 | 96 | 96(A) | 96(A) | 4 | |||
27 | |||||||
28 | |||||||
29 | 12 | 19 | |||||
30 | 22 | ||||||
31 | |||||||
32 |
compiled by Thierry Le Gleuher & Alain Brobecker, march 2007
This page shows retrograde analysis problems where the solver is asked to find the last N single moves played to reach the position. The design objective is to maximize N and minimize the total number of units, M. Records are positions where one can improve neither of M or N, without worsening the other.
This is an extension of the "Last move" task, discussed in several webpages. Records are classified in the following six categories:
The number in the first column is M. Then there is one column per problem type, T. The non-blank cells show the records: the cell (M, T) contains the value of N.
When a record also applies to a less restrictive type, then the cell instead contains the letter referring to the least restrictive type.
In some cases, a record for Type C, apart from the last move, can also apply as a record for Type B: this is denoted C or Cx depending on whether the last move was a capture.
The problems here are also available from Alain as a pdf.