MathDB
Flights between cities (Turkey 2004)

Source:

November 19, 2010
combinatorics proposedcombinatorics

Problem Statement

Two-way flights are operated between 8080 cities in such a way that each city is connected to at least 77 other cities by a direct flight and any two cities are connected by a finite sequence of flights. Find the smallest kk such that for any such arrangement of flights it is possible to travel from any city to any other city by a sequence of at most kk flights.