a tourist visits Complant (silk road combo)
Source: SRMC 2009
September 2, 2018
combinatorics
Problem Statement
A tourist going to visit the Complant, found that:
a) in this country cities, numbered by integers from to ,
b) two cities with numbers and are connected by a straight line if and only if the binary entries of numbers and they differ exactly in one digit,
c) during the stay of a tourist in that country roads will be closed for scheduled repairs.
Prove that a tourist can make a closed route along the existing roads of Complant, passing through each of its cities exactly once.