VertexCoverByRounding

1. Let x be a min-cost fractional vertex cover.
2. Return the set S of vertices v having x(v) ≥ 1/2.

prove: The set S of vertices is a vertex cover.

prove: The cost of S is at most twice the minimum cost of any vertex cover.

prove: The IntegralityGap of the above integer linear program for min-cost vertex cover is 2.