simplify case of 2 terminals

src/paths/steiner.cpp

@@ -207,28 +207,15 @@ igraph_error_t igraph_steiner_dreyfus_wagner(
         *res = 0.0;
         flag_terminals = true;
     } else if (no_of_terminals == 2) {
-        igraph_vector_int_t vertices;
-        igraph_real_t tree_weight = 0.0;
-        igraph_vector_int_t edges_res;
-
-        IGRAPH_VECTOR_INT_INIT_FINALLY(&vertices, 0);
-        IGRAPH_VECTOR_INT_INIT_FINALLY(&edges_res, 0);
-
         IGRAPH_CHECK(igraph_get_shortest_path_dijkstra(
-                    graph, &vertices, &edges_res, VECTOR(*terminals)[0],
+                    graph, NULL, res_tree, VECTOR(*terminals)[0],
                     VECTOR(*terminals)[1], pweights, IGRAPH_ALL));
-        igraph_integer_t tree_size = igraph_vector_int_size(&edges_res);
+        igraph_integer_t tree_size = igraph_vector_int_size(res_tree);
 
+        *res = 0.0;
         for (igraph_integer_t i = 0; i < tree_size; i++) {
-            tree_weight += VECTOR(*pweights)[VECTOR(edges_res)[i]];
+            *res += VECTOR(*pweights)[VECTOR(*res_tree)[i]];
         }
-        *res = tree_weight;
-
-        IGRAPH_CHECK(igraph_vector_int_append(res_tree, &edges_res));
-
-        igraph_vector_int_destroy(&vertices);
-        igraph_vector_int_destroy(&edges_res);
-        IGRAPH_FINALLY_CLEAN(2);
 
         flag_terminals = true;
     }