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+/**
+ * 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);
+}
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