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Schlagwörter:
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Zusammenfassung:
The problem of finding the minimum size 2-connected subgraph is
a classical problem in network design. It is known to be NP-hard even on
cubic planar graphs and Max-SNP hard.
We study the generalization of this problem, where requirements of 1 or 2
edge or vertex disjoint paths are specified between every pair of vertices,
and the aim is to find a minimum subgraph satisfying these requirements.
For both problems we give $3/2$-approximation algorithms. This improves on
the straightforward $2$-approximation algorithms for these problems, and
generalizes earlier results for 2-connectivity.
We also give analyses of the classical local optimization heuristics for
these two network design problems.