horizontal and vertical segments intersected by curves
Source: Miklos Schweitzer 2020, Problem 4
December 1, 2020
geometrycombinatorics
Problem Statement
Consider horizontal and vertical segments in the plane that may intersect each other. Let denote their total number. Suppose that we have curves starting from the origin that are pairwise disjoint except for their endpoints. Assume that each curve intersects exactly two of the segments, a different pair for each curve. Prove that .