Maximum balanced subgraph problem parameterized above lower bound

  • Authors:
  • R. Crowston;G. Gutin;M. Jones;G. Muciaccia

  • Affiliations:
  • -;-;-;-

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2013

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Abstract

We consider graphs without loops or parallel edges in which every edge is assigned + or -. Such a signed graph is balanced if its vertex set can be partitioned into parts V"1 and V"2 such that all edges between vertices in the same part have sign + and all edges between vertices of different parts have sign - (one of the parts may be empty). It is well-known that every connected signed graph with n vertices and m edges has a balanced subgraph with at least m2+n-14 edges and this bound is tight. We consider the following parameterized problem: given a connected signed graph G with n vertices and m edges, decide whether G has a balanced subgraph with at least m2+n-14+k4 edges, where k is the parameter. We obtain an algorithm for the problem of runtime 8^k(kn)^O^(^1^). We also prove that for each instance (G,k) of the problem, in polynomial time, we can either solve (G,k) or produce an equivalent instance (G^',k^') such that k^'=