MathDB
TOT 064 1984 Spring S-O5 S-A1 game with soldiers on a 20x20 table

Source:

August 19, 2019
game strategygameminimumcombinatoricssquare table

Problem Statement

(a) On each square of a squared sheet of paper of size 20×2020 \times 20 there is a soldier. Vanya chooses a number dd and Petya moves the soldiers to new squares in such a way that each soldier is moved through a distance of at least dd (the distance being measured between the centres of the initial and the new squares) and each square is occupied by exactly one soldier. For which dd is this possible? (Give the maximum possible dd, prove that it is possible to move the soldiers through distances not less than dd and prove that there is no greater dd for which this procedure may be carried out.) (b) Answer the same question as (a), but with a sheet of size 21×2121 \times 21.
(SS Krotov, Moscow)