/* -*- mode: C -*- */
/*
IGraph library.
Copyright (C) 2014 Gabor Csardi <csardi.gabor@gmail.com>
334 Harvard street, Cambridge, MA 02139 USA
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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "igraph_interface.h"
#include "igraph_interrupt_internal.h"
#include "igraph_vector_ptr.h"
#include "igraph_iterators.h"
#include "igraph_adjlist.h"
#include "igraph_stack.h"
/**
* \function igraph_get_all_simple_paths
* List all simple paths from one source
*
* A path is simple, if its vertices are unique, no vertex
* is visited more than once.
*
* </para><para>
* Note that potentially there are exponentially many
* paths between two vertices of a graph, and you may
* run out of memory when using this function, if your
* graph is lattice-like.
*
* </para><para>
* This function currently ignored multiple and loop edges.
* \param graph The input graph.
* \param res Initialized integer vector, all paths are
* returned here, separated by -1 markers. The paths
* are included in arbitrary order, as they are found.
* \param from The start vertex.
* \param to The target vertices.
* \param cutoff Maximum length of path that is considered. If
* negative, paths of all lengths are considered.
* \param mode The type of the paths to consider, it is ignored
* for undirected graphs.
* \return Error code.
*
* Time complexity: O(n!) in the worst case, n is the number of
* vertices.
*/
int igraph_get_all_simple_paths(const igraph_t *graph,
igraph_vector_int_t *res,
igraph_integer_t from,
const igraph_vs_t to,
igraph_integer_t cutoff,
igraph_neimode_t mode) {
igraph_integer_t no_nodes = igraph_vcount(graph);
igraph_vit_t vit;
igraph_bool_t toall = igraph_vs_is_all(&to);
igraph_vector_char_t markto;
igraph_lazy_adjlist_t adjlist;
igraph_vector_int_t stack, dist;
igraph_vector_char_t added;
igraph_vector_int_t nptr;
int iteration;
if (from < 0 || from >= no_nodes) {
IGRAPH_ERROR("Invalid starting vertex", IGRAPH_EINVAL);
}
if (!toall) {
igraph_vector_char_init(&markto, no_nodes);
IGRAPH_FINALLY(igraph_vector_char_destroy, &markto);
IGRAPH_CHECK(igraph_vit_create(graph, to, &vit));
IGRAPH_FINALLY(igraph_vit_destroy, &vit);
for (; !IGRAPH_VIT_END(vit); IGRAPH_VIT_NEXT(vit)) {
VECTOR(markto)[ IGRAPH_VIT_GET(vit) ] = 1;
}
igraph_vit_destroy(&vit);
IGRAPH_FINALLY_CLEAN(1);
}
IGRAPH_CHECK(igraph_vector_char_init(&added, no_nodes));
IGRAPH_FINALLY(igraph_vector_char_destroy, &added);
IGRAPH_CHECK(igraph_vector_int_init(&stack, 100));
IGRAPH_FINALLY(igraph_vector_int_destroy, &stack);
IGRAPH_CHECK(igraph_vector_int_init(&dist, 100));
IGRAPH_FINALLY(igraph_vector_int_destroy, &dist);
IGRAPH_CHECK(igraph_lazy_adjlist_init(graph, &adjlist, mode,
/*simplify=*/ 1));
IGRAPH_FINALLY(igraph_lazy_adjlist_destroy, &adjlist);
IGRAPH_CHECK(igraph_vector_int_init(&nptr, no_nodes));
IGRAPH_FINALLY(igraph_vector_int_destroy, &nptr);
igraph_vector_int_clear(res);
igraph_vector_int_clear(&stack);
igraph_vector_int_clear(&dist);
igraph_vector_int_push_back(&stack, from);
igraph_vector_int_push_back(&dist, 0);
VECTOR(added)[from] = 1;
while (!igraph_vector_int_empty(&stack)) {
int act = igraph_vector_int_tail(&stack);
int curdist = igraph_vector_int_tail(&dist);
igraph_vector_t *neis = igraph_lazy_adjlist_get(&adjlist, act);
int n = igraph_vector_size(neis);
int *ptr = igraph_vector_int_e_ptr(&nptr, act);
igraph_bool_t any;
igraph_bool_t within_dist;
int nei;
if (iteration == 0) {
IGRAPH_ALLOW_INTERRUPTION();
}
within_dist = (curdist < cutoff || cutoff < 0);
if (within_dist) {
/* Search for a neighbor that was not yet visited */
any = 0;
while (!any && (*ptr) < n) {
nei = (int) VECTOR(*neis)[(*ptr)];
any = !VECTOR(added)[nei];
(*ptr) ++;
}
}
if (within_dist && any) {
/* There is such a neighbor, add it */
IGRAPH_CHECK(igraph_vector_int_push_back(&stack, nei));
IGRAPH_CHECK(igraph_vector_int_push_back(&dist, curdist + 1));
VECTOR(added)[nei] = 1;
/* Add to results */
if (toall || VECTOR(markto)[nei]) {
IGRAPH_CHECK(igraph_vector_int_append(res, &stack));
IGRAPH_CHECK(igraph_vector_int_push_back(res, -1));
}
} else {
/* There is no such neighbor, finished with the subtree */
int up = igraph_vector_int_pop_back(&stack);
igraph_vector_int_pop_back(&dist);
VECTOR(added)[up] = 0;
VECTOR(nptr)[up] = 0;
}
iteration++;
if (iteration >= 10000) {
iteration = 0;
}
}
igraph_vector_int_destroy(&nptr);
igraph_lazy_adjlist_destroy(&adjlist);
igraph_vector_int_destroy(&dist);
igraph_vector_int_destroy(&stack);
igraph_vector_char_destroy(&added);
IGRAPH_FINALLY_CLEAN(5);
if (!toall) {
igraph_vector_char_destroy(&markto);
IGRAPH_FINALLY_CLEAN(1);
}
return 0;
}