KCoreComponents

KCoreComponents[g,k] gives the k-core components of the underlying simple graph of g.

KCoreComponents[g,k,"In"] gives the k-core components with vertex in-degrees at least k.

KCoreComponents[g,k,"Out"] gives the k-core components with vertex out-degrees at least k.

KCoreComponents[{v->w,…},…] uses rules v->w to specify the graph g. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.