Basic lines in rectangular partition
Source: China Mathematical Olympiad 2017 Q3
November 23, 2016
rectanglecombinatorial geometrycombinatoricsChina
Problem Statement
Consider a rectangle partitioned into smaller rectangles such that the sides of each smaller rectangle is parallel to one of the sides of the original rectangle. Call the corners of each rectangle a vertex. For any segment joining two vertices, call it basic if no other vertex lie on it. (The segments must be part of the partitioning.) Find the maximum/minimum possible number of basic segments over all possible partitions of .