In this paper, we give a short survey on discrete geometry on red and blue points in the plane, most of whose results were obtained in the past decade. We consider balanced subdivision problems, geometric graph problems, graph embedding problems, Gallai-type problems and others. In this paper, we give a short survey on discrete geometry on red and blue… (More)
Let G be a graph. The core of G, denoted by G ∆ , is the subgraph of G induced by the vertices of degree ∆(G), where ∆(G) denotes the maximum degree of G. A k-edge coloring of G is a function f : E(G) → L such that |L| = k and f (e 1) = f (e 2) for all two adjacent edges e 1 and e 2 of G. The chromatic index of G, denoted by χ (G), is the minimum number k… (More)
The tree partition number of an r-edge-colored graph G, denoted by t r (G), is the minimum number k such that whenever the edges of G are colored with r colors, the vertices of G can be covered by at most k vertex-disjoint monochromatic trees. We determine t 2 (K(n 1 , n 2 ,. .. , n k)) of the complete k-partite graph K(n 1 , n 2 ,. .. , n k). In… (More)
Given n red and n blue points in the plane and a planar straight line matching between the red and the blue points, the matching can be extended into a bipartite planar straight line spanning tree. That is, any red-blue planar matching can be completed into a crossing-free red-blue spanning tree. Such a tree can be constructed in O(n log n) time.
Let P 1 , ..., P k be a collection of disjoint point sets in 2 in general position. We prove that for each 1 ≤ i ≤ k we can find a plane spanning tree T i of P i such that the edges of T 1 , ..., T k intersect at most (k − 1)(n − k) + (k)(k−1) 2 , where n is the number of points in P 1 ∪ ... ∪ P k. If the intersection of the convex hulls of P 1 , ..., P k… (More)
Let X be a set of multicolored points in the plane such that no three points are collinear and each color appears on at most ⌈|X|/2⌉ points. We show the existence of a non-crossing properly colored geometric perfect matching on X (if |X| is even), and the existence of a non-crossing properly colored geometric spanning tree with maximum degree at most 3 on… (More)