/**
* 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 3 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
* <http://www.gnu.org/licenses/>.
*
* (c) Vincenzo Nicosia 2009-2017 -- <v.nicosia@qmul.ac.uk>
*
* This file is part of NetBunch, a package for complex network
* analysis and modelling. For more information please visit:
*
* http://www.complex-networks.net/
*
* If you use this software, please add a reference to
*
* V. Latora, V. Nicosia, G. Russo
* "Complex Networks: Principles, Methods and Applications"
* Cambridge University Press (2017)
* ISBN: 9781107103184
*
***********************************************************************
*
* This program finds the (size of the) strongly connected components
* of a directed graph given as input. We use the Kosaraju-Sharir
* algorithm, which performs two DFS scans of the graph, the first
* time using the original DFS algorithm on the graph, and the second
* time using the transposed graph and a slightly modified version of
* "components", which traverses the nodes of the graph in descending
* order of finishing time.
*
*
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "utils.h"
void usage(char *argv[]){
printf("********************************************************************\n"
"** **\n"
"** -*- strong_conn -*- **\n"
"** **\n"
"** Find the strongly connected components of a directed graph **\n"
"** and print on output their size and/or the list of nodes **\n"
"** belonging to each component. The first parameter 'graph_in' **\n"
"** is the name of the file containing the edge list of the **\n"
"** graph. **\n"
"** **\n"
"** If 'graph_in' is equal to '-' (dash), read the edge list **\n"
"** from standard input (STDIN). **\n"
"** **\n"
"** The program prints on output the SIZE of each strongly **\n"
"** connected component of the graph, one per line: **\n"
"** **\n"
"** size_1 **\n"
"** size_2 **\n"
"** size_3 **\n"
"** **\n"
"** The sizes are in no particular order. **\n"
"** **\n"
"** If 'SHOW' is given as second argument, the list of nodes **\n"
"** belonging to each component is printed as well, in the **\n"
"** format: **\n"
"** **\n"
"** size_1: node_1 node_2 node_3 .... **\n"
"** size_2: node_1 node_2 node_3 .... **\n"
"** size_3: node_1 node_2 node_3 .... **\n"
"** **\n"
"** **\n"
"********************************************************************\n"
" This is Free Software - You can use and distribute it under \n"
" the terms of the GNU General Public License, version 3 or later\n\n"
" Please visit http://www.complex-networks.net for more information\n\n"
" (c) Vincenzo Nicosia 2010-2017 (v.nicosia@qmul.ac.uk)\n"
"********************************************************************\n\n"
);
printf("Usage: %s <graph_in> [SHOW]\n\n" , argv[0]);
}
int dfs(unsigned int i, unsigned int *J_slap, unsigned int *r_slap,
unsigned int N, unsigned int nc,
unsigned int *ic, unsigned int *f,
char reset){
static unsigned int time = 0;
unsigned int j, s;
if(reset){
time = 0;
}
ic[i] = nc;
s = 1;
for(j=r_slap[i]; j<r_slap[i+1]; j++){
if (ic[J_slap[j]] == 0){
s += dfs(J_slap[j], J_slap, r_slap, N, nc, ic, f, 0);
}
}
f[time] = i;
time += 1;
return s;
}
/**
*
* Find all the components of the given graph
*
*/
int components(unsigned int *J_slap, unsigned int *r_slap,
unsigned int N, unsigned int **ic,
unsigned int **f, unsigned int **sizes){
unsigned int nc, s;
unsigned int i;
*ic = malloc(N * sizeof(unsigned int));
*f = malloc(N * sizeof(unsigned int));
*sizes = malloc(N * sizeof(unsigned int));
for(i=0; i<N; i++){
(*ic)[i] = 0;
(*f)[i] = 0;
}
nc = 0;
for(i=0; i<N; i++){
while( (*ic) [i] != 0 && i < N)
i += 1;
if (i == N)
break;
nc += 1;
if (nc ==1){
s = dfs(i, J_slap, r_slap, N, nc, *ic, *f, 1);
}
else{
s = dfs(i, J_slap, r_slap, N, nc, *ic, *f, 0);
}
//printf("s: %d\n", s);
(*sizes)[nc] = s;
}
return nc;
}
/**
*
* Find the components of the transposed graph, where the nodes are
* visited in descending order of their finishing time
*
*/
int components_rev(unsigned int *J_slap, unsigned int *r_slap,
unsigned int N, unsigned int **ic,
unsigned int *f, unsigned int **f_T, unsigned int **sizes){
unsigned int nc, s;
unsigned int idx;
int i;
*ic = malloc(N * sizeof(unsigned int));
*f_T = malloc(N * sizeof(unsigned int));
*sizes = malloc((N+1) * sizeof(unsigned int));
for(i=0; i<N; i++){
(*ic)[i] = 0;
}
nc = 0;
for(i=N-1; i>=0; i--){
idx = f[i];
while( i >0 && (*ic) [idx] != 0 ){
i -= 1;
idx = f[i];
}
if (i < 0)
break;
nc += 1;
if (nc == 1){
s = dfs(idx, J_slap, r_slap, N, nc, *ic, *f_T, 1);
}
else{
s = dfs(idx, J_slap, r_slap, N, nc, *ic, *f_T, 1);
}
(*sizes)[nc] = s;
}
return nc;
}
int main(int argc, char *argv[]){
FILE *filein;
unsigned int N, K, N1, N2;
unsigned int *I, *J, *J_slap, *r_slap, *J_slap_T, *r_slap_T;
unsigned int *ic, *f, *sizes, *ic_T, *f_T, *sizes_T;
unsigned int i, j, nc_T;
char show = 0;
if (argc < 2){
usage(argv);
exit(1);
}
if (argc == 3 && !my_strcasecmp("SHOW", argv[2])){
show = 1;
}
if (!strcmp(argv[1], "-")){
/* take the input from STDIN */
filein = stdin;
}
else {
filein = openfile_or_exit(argv[1], "r", 2);
}
I = J = NULL;
K = read_ij(filein, &I, &J);
J_slap = J_slap_T = NULL;
r_slap = r_slap_T = NULL;
/* obtain the SLAP representation of the graph */
N1 = convert_ij2slap(I, J, K, &r_slap, &J_slap);
/* obtain the SLAP representation of the transposed graph */
N2 = convert_ij2slap(J, I, K, &r_slap_T, &J_slap_T);
N = N1 >= N2 ? N1 : N2;
components(J_slap, r_slap, N, &ic, &f, &sizes);
fclose(filein);
nc_T = components_rev(J_slap_T, r_slap_T, N, &ic_T, f, &f_T, &sizes_T);
for(i=1; i<=nc_T; i++){
printf("%d", sizes_T[i]);
if (show){
printf(":");
for(j=0; j<N; j++){
if (ic_T[j] == i){
printf(" %d", j);
}
}
printf("\n");
}
else{
printf("\n");
}
}
free(J_slap);
free(r_slap);
free(J_slap_T);
free(r_slap_T);
free(ic);
free(f);
free(sizes);
free(ic_T);
free(f_T);
free(sizes_T);
free(I);
free(J);
}