Abstract
In this article we provide hardness results and approximation algorithms for the following three natural degree-constrained subgraph problems, which take as input an undirected graph G=(V,E). Let d>=2 be a fixed integer. The Maximumd-degree-bounded Connected Subgraph (MDBCS"d) problem takes as additional input a weight function @w:E->R^+, and asks for a subset E^'@?E such that the subgraph induced by E^' is connected, has maximum degree at most d, and @?"e"@?"E"^"'@w(e) is maximized. The Minimum Subgraph of Minimum Degree>=d (MSMD"d) problem involves finding a smallest subgraph of G with minimum degree at least d. Finally, the Dual Degree-densek-Subgraph (DDDkS) problem consists in finding a subgraph H of G such that |V(H)|@?k and the minimum degree in H is maximized.