指标1：minimum vertex-cut By a vertex-cut in a graph G,we mean a set U of vertices of G such that G-U is disconnected.A vertex- cut of minimum cardinality in G is called a minimum vertex-cut.指标1：minimum vertex-cut By a vertex-cut in a graph G, we mean a set U of vertices of G such that G - U is disconnected. A vertex￾cut of minimum cardinality in G is called a minimum vertex-cut