Sufficient Conditions for the
Existence of Perfect
Heterochromatic Matchings
in Colored Graphs
Lin Hu and Xueliang Li
Center for Combinatorics and LPMC,
Nankai University, Tianjin 300071, P.R. China
Abstract
Let G=(V,E) be an
(edge-)colored graph, i.e., G is assigned a mapping C:E
{1,2,...,r}, the set of colors. A matching
of G is called heterochromatic if its any two edges have
different colors. Unlike uncolored matchings for which the maximum
matching problem is solvable in polynomial time, the maximum
heterochromatic matching problem is NP-complete. This means that
to find both sufficient and necessary good conditions for the
existence of perfect heterochromatic matchings should be not easy.
In this paper, we obtain sufficient conditions of Hall-type and
Tutte-type for the existence of perfect heterochromatic matchings
in colored bipartite graphs and general colored graphs by showing
that a colored bipartite graph B=(X,Y) contains a
heterochromatic matching that saturates all vertices in X if
|Nc(S)|
|S| for all S
X, and a general
colored graph G contains a perfect heterochromatic matching if
|Nc(S)|
|S| for all S
V such that
0
|S|
|V|/2 and |N(S)\
S|
|S|. We also obtain a sufficient and necessary
condition of Berge-type to verify if a heterochromatic matching
M of G is maximum, i.e., if and only if there does not exist
any heterochromatic M-augmenting path system in G.