feat: is_biconnected()

DESCRIPTION

@@ -70,5 +70,5 @@ Config/testthat/start-first: vs-es, scan, vs-operators, weakref,
     watts.strogatz.game
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.3.0.9000
+RoxygenNote: 7.3.1
 SystemRequirements: gmp, libxml2, glpk (>= 4.57)

NAMESPACE

@@ -536,6 +536,7 @@ export(is.separator)
 export(is.simple)
 export(is.weighted)
 export(is_acyclic)
+export(is_biconnected)
 export(is_bipartite)
 export(is_chordal)
 export(is_connected)

R/aaa-auto.R

@@ -215,6 +215,21 @@ realize_degree_sequence_impl <- function(out.deg, in.deg=NULL, allowed.edge.type
   res
 }
 
+realize_bipartite_degree_sequence_impl <- function(degrees1, degrees2, allowed.edge.types=c("simple", "loops", "multi", "all"), method=c("smallest", "largest", "index")) {
+  # Argument checks
+  degrees1 <- as.numeric(degrees1)
+  degrees2 <- as.numeric(degrees2)
+  allowed.edge.types <- switch(igraph.match.arg(allowed.edge.types),
+    "simple"=0L, "loop"=1L, "loops"=1L, "multi"=6L, "multiple"=6L, "all"=7L)
+  method <- switch(igraph.match.arg(method), "smallest"=0L, "largest"=1L, "index"=2L)
+
+  on.exit( .Call(R_igraph_finalizer) )
+  # Function call
+  res <- .Call(R_igraph_realize_bipartite_degree_sequence, degrees1, degrees2, allowed.edge.types, method)
+
+  res
+}
+
 circulant_impl <- function(n, shifts, directed=FALSE) {
   # Argument checks
   n <- as.numeric(n)
@@ -2257,6 +2272,17 @@ bridges_impl <- function(graph) {
   res
 }
 
+is_biconnected_impl <- function(graph) {
+  # Argument checks
+  ensure_igraph(graph)
+
+  on.exit( .Call(R_igraph_finalizer) )
+  # Function call
+  res <- .Call(R_igraph_is_biconnected, graph)
+
+  res
+}
+
 cliques_impl <- function(graph, min=0, max=0) {
   # Argument checks
   ensure_igraph(graph)

R/components.R

@@ -274,6 +274,32 @@ bridges <- bridges_impl
 biconnected_components <- biconnected_components_impl
 
 
+#' Check biconnectedness
+#'
+#' Tests whether a graph is biconnected.
+#'
+#' A graph is biconnected if the removal of any single vertex (and its adjacent
+#' edges) does not disconnect it.
+#'
+#' igraph does not consider single-vertex graphs biconnected.
+#'
+#' Note that some authors do not consider the graph consisting of
+#' two connected vertices as biconnected, however, igraph does.
+#'
+#' @param graph The input graph. Edge directions are ignored.
+#' @return Logical, `TRUE` if the graph is biconnected.
+#' @seealso [articulation_points()], [biconnected_components()],
+#' [is_connected()], [vertex_connectivity()]
+#' @keywords graphs
+#' @examples
+#'
+#' is_biconnected(make_graph("bull"))
+#' is_biconnected(make_graph("dodecahedron"))
+#' @family components
+#' @export
+is_biconnected <- is_biconnected_impl
+
+
 #' @rdname components
 #' @export
 largest_component <- function(graph, mode = c("weak", "strong")) {

src/rinterface.c

@@ -788,6 +788,44 @@ SEXP R_igraph_realize_degree_sequence(SEXP out_deg, SEXP in_deg, SEXP allowed_ed
   return(r_result);
 }
 
+/*-------------------------------------------/
+/ igraph_realize_bipartite_degree_sequence   /
+/-------------------------------------------*/
+SEXP R_igraph_realize_bipartite_degree_sequence(SEXP degrees1, SEXP degrees2, SEXP allowed_edge_types, SEXP method) {
+                                        /* Declarations */
+  igraph_t c_graph;
+  igraph_vector_int_t c_degrees1;
+  igraph_vector_int_t c_degrees2;
+  igraph_edge_type_sw_t c_allowed_edge_types;
+  igraph_realize_degseq_t c_method;
+  SEXP graph;
+
+  SEXP r_result;
+                                        /* Convert input */
+  R_SEXP_to_vector_int_copy(degrees1, &c_degrees1);
+  IGRAPH_FINALLY(igraph_vector_int_destroy, &c_degrees1);
+  R_SEXP_to_vector_int_copy(degrees2, &c_degrees2);
+  IGRAPH_FINALLY(igraph_vector_int_destroy, &c_degrees2);
+  c_allowed_edge_types = (igraph_edge_type_sw_t) Rf_asInteger(allowed_edge_types);
+  c_method = (igraph_realize_degseq_t) Rf_asInteger(method);
+                                        /* Call igraph */
+  IGRAPH_R_CHECK(igraph_realize_bipartite_degree_sequence(&c_graph, &c_degrees1, &c_degrees2, c_allowed_edge_types, c_method));
+
+                                        /* Convert output */
+  IGRAPH_FINALLY(igraph_destroy, &c_graph);
+  PROTECT(graph=R_igraph_to_SEXP(&c_graph));
+  IGRAPH_I_DESTROY(&c_graph);
+  IGRAPH_FINALLY_CLEAN(1);
+  igraph_vector_int_destroy(&c_degrees1);
+  IGRAPH_FINALLY_CLEAN(1);
+  igraph_vector_int_destroy(&c_degrees2);
+  IGRAPH_FINALLY_CLEAN(1);
+  r_result = graph;
+
+  UNPROTECT(1);
+  return(r_result);
+}
+
 /*-------------------------------------------/
 / igraph_circulant                           /
 /-------------------------------------------*/
@@ -6222,6 +6260,30 @@ SEXP R_igraph_bridges(SEXP graph) {
   return(r_result);
 }
 
+/*-------------------------------------------/
+/ igraph_is_biconnected                      /
+/-------------------------------------------*/
+SEXP R_igraph_is_biconnected(SEXP graph) {
+                                        /* Declarations */
+  igraph_t c_graph;
+  igraph_bool_t c_res;
+  SEXP res;
+
+  SEXP r_result;
+                                        /* Convert input */
+  R_SEXP_to_igraph(graph, &c_graph);
+                                        /* Call igraph */
+  IGRAPH_R_CHECK(igraph_is_biconnected(&c_graph, &c_res));
+
+                                        /* Convert output */
+  PROTECT(res=NEW_LOGICAL(1));
+  LOGICAL(res)[0]=c_res;
+  r_result = res;
+
+  UNPROTECT(1);
+  return(r_result);
+}
+
 /*-------------------------------------------/
 / igraph_cliques                             /
 /-------------------------------------------*/