|igraph Reference Manual|
igraph_subcomponent— The vertices in the same component as a given vertex.
igraph_subgraph— Creates a subgraph with the specified vertices.
igraph_clusters— Calculates the (weakly or strongly) connected components in a graph.
igraph_is_connected— Decides whether the graph is (weakly or strongly) connected.
igraph_decompose— Decompose a graph into connected components.
igraph_biconnected_components— Calculate biconnected components
igraph_articulation_points— Find the articulation points in a graph.