MathDB
Union of two neighbourhoods

Source: Own. Malaysian SST 2023 P8

August 27, 2023
combinatorics

Problem Statement

Given two positive integers mm and nn, find the largest kk in terms of mm and nn such that the following condition holds:
Any tree graph GG with kk vertices has two (possibly equal) vertices uu and vv such that for any other vertex ww in GG, either there is a path of length at most mm from uu to ww, or there is a path of length at most nn from vv to ww.
Proposed by Ivan Chan Kai Chin