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/*
IGraph library.
Copyright (C) 2021 The igraph development team <igraph@igraph.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include <igraph.h>
#include "test_utilities.h"
int main(void) {
igraph_t graph, spanning_tree;
igraph_vector_int_t tree_edges;
igraph_bool_t is_tree;
int err;
igraph_rng_seed(igraph_rng_default(), 987);
igraph_vector_int_init(&tree_edges, 0);
/* This is guaranteed to create a connected graph. */
igraph_barabasi_game(&graph, 100, 2, 2, NULL, 0, 1, IGRAPH_UNDIRECTED, IGRAPH_BARABASI_PSUMTREE, NULL);
err = igraph_random_spanning_tree(&graph, &tree_edges, 0);
IGRAPH_ASSERT(!err);
IGRAPH_ASSERT(igraph_vector_int_size(&tree_edges) == igraph_vcount(&graph) - 1);
err = igraph_subgraph_edges(&graph, &spanning_tree, igraph_ess_vector(&tree_edges), /* delete_vertices= */ 0);
IGRAPH_ASSERT(!err);
IGRAPH_ASSERT(igraph_vcount(&spanning_tree) == igraph_vcount(&graph));
igraph_is_tree(&spanning_tree, &is_tree, NULL, IGRAPH_ALL);
IGRAPH_ASSERT(is_tree);
igraph_destroy(&spanning_tree);
igraph_destroy(&graph);
/* Non-connected forest graph. There is only one solution. */
igraph_small(&graph, 4, IGRAPH_UNDIRECTED, 0,1, 2,3, -1);
/* Find a spanning tree of the component containing vertex 0 */
err = igraph_random_spanning_tree(&graph, &tree_edges, 0);
IGRAPH_ASSERT(!err);
IGRAPH_ASSERT(igraph_vector_int_size(&tree_edges) == 1);
IGRAPH_ASSERT(VECTOR(tree_edges)[0] == 0);
/* Find a spanning forest */
err = igraph_random_spanning_tree(&graph, &tree_edges, -1);
IGRAPH_ASSERT(!err);
IGRAPH_ASSERT(igraph_vector_int_size(&tree_edges) == 2);
IGRAPH_ASSERT(VECTOR(tree_edges)[0] == 0 && VECTOR(tree_edges)[1] == 1);
igraph_destroy(&graph);
igraph_vector_int_destroy(&tree_edges);
VERIFY_FINALLY_STACK();
return 0;
}
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