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Given an undirected connected graph, our goal is to remove some edges to make the graph disconnected. The constraint is that each node of the graph can not lose more than $m$ edges incident to it. I want to find the minimum $m$ for which the goal is achievable. Is there any efficient algorithm to compute this minimum $m$ (and/or which edges to remove)? Or is it NP-complete?

flag	asked Dec 1 2009 at 0:15 Sheldoniz 83●4

David Eppstein · Accepted Answer · 2009-12-01 01:32:52Z UTC

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It appears to be NP-complete even when m=1: see The Complexity of the Matching-Cut Problem, Maurizio Patrignani and Maurizio Pizzonia, WG 2001, http://dx.doi.org/10.1007/3-540-45477-2_26

answered Dec 1 2009 at 1:32

David Eppstein
9,233●1●21●41

It's even NP-complete with m = 1 and restricted to planar graphs, see portal.acm.org/citation.cfm?id=1598870. This also gives some classes of graphs for which there is a polynomial-time algorithm, though I suspect the constants can be huge (bounded tree-width?!). – Harrison Brown Dec 1 2009 at 6:03

Carter Tazio Schonwald · Answer 2 · 2009-12-01 07:49:17Z UTC

According to wikipedia, if your only constraint is minimizing the number of edges removes, it's easy. Now whether those algorithms are approriate for solving your problem as stated exactly or approximately, thats another question entirely. I'd guess that it's certainly easy (in at least one of an exact or approximate sense) as long as the graphs have some nice sparseness or geometric structure such as being planar or k regular.

A graph connectivity problem (restated)

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