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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 computes the distance from a given node to all the
* other nodes of an undirected graph, using the Breadth-First Search
* algorithm.
*
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "utils.h"
void usage(char *argv[]){
printf("********************************************************************\n"
"** **\n"
"** -*- shortest -*- **\n"
"** **\n"
"** Compute the distance from the given 'node' to all the other **\n"
"** nodes of an undirected graph. The first parameter 'graph_in' **\n"
"** is the name of the file containing the edge list of the **\n"
"** graph. The second parameter 'node' is the label of the node **\n"
"** for which we want to compute the distances to all the other **\n"
"** nodes. **\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 a row of values: **\n"
"** **\n"
"** d0 d1 d2 d3 d4...... **\n"
"** **\n"
"** where d0 is the distance between 'node' and '0', 'd1' is the **\n"
"** distance between 'node' and '1', and so on. **\n"
"** **\n"
"** If the third parameter is equal to 'SHOW', the program will **\n"
"** dump all the shortest paths from 'node' to all the other **\n"
"** nodes on the standard error (STDERR). **\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 2009-2017 (v.nicosia@qmul.ac.uk)\n"
"********************************************************************\n\n"
);
printf("Usage: %s <graph_in> <node> [SHOW]\n\n" , argv[0]);
}
/*
* Add 'k' to a list of predecessors
*/
void add_predecessor(unsigned int **pred, unsigned int k){
(*pred)[0] += 1;
*pred = realloc(*pred, ((*pred)[0] + 1) * sizeof(unsigned int));
(*pred)[ (*pred)[0] ] = k;
}
/*
*
* This is the implementation of the Breadth-First Search algorithm
* (BFS) to compute the shortest paths, and the distances, between a
* given node 'i' and all the other nodes of a graph.
*
*/
unsigned int** compute_shortest_paths(unsigned int N, unsigned int *J_slap, unsigned int *r_slap,
unsigned int i, unsigned int **dist){
unsigned int j, k, cur_node;
unsigned int *marked, **preds;
unsigned int d;
unsigned int n, nd, ndp;
*dist = malloc(N * sizeof(unsigned int));
marked = malloc(N * sizeof(unsigned int));
preds = malloc(N * sizeof(unsigned int *));
for(j=0; j<N; j ++){
(*dist)[j] = N;
preds[j] = malloc(sizeof(unsigned int));
preds[j][0] = 0; /* The list of predecessors is empty! */
}
(*dist)[i] = 0;
marked[0] = i;
d = 0;
n = 0;
nd = 1;
ndp = 0;
while (d<N && nd > 0){
for(k = n; k< n+nd; k ++){
cur_node = marked[k];
for (j=r_slap[cur_node]; j<r_slap[cur_node +1] ; j++){
if ( (*dist)[ J_slap[j] ] == d+1){
add_predecessor((unsigned int **)(preds + J_slap[j]), cur_node);
}
if ( (*dist)[ J_slap[j] ] == N){
(*dist)[ J_slap[j] ] = d+1;
marked[n + nd + ndp] = J_slap[j];
add_predecessor(preds + J_slap[j], cur_node);
ndp +=1;
}
}
}
n = n + nd;
nd = ndp;
ndp = 0;
d += 1;
}
free(marked);
return preds;
}
/*
* Dump on output the distances between 'node' and all the other nodes
* of the graph
*
*/
void dump_dists(unsigned int *dists, unsigned int N){
unsigned int i;
for (i=0; i<N; i++){
printf("%d ", dists[i]);
}
printf("\n");
}
/*
* recursively show the shortest paths from 'node' to all the other
* nodes ot the graph
*
*/
void recursive_show_paths(unsigned int **preds, unsigned int N, unsigned int k,
char *buff, int pos, FILE *fileout){
int i;
char lbuff[10];
if (preds[k][0] == 0){
sprintf(buff + pos, "%5d\n", k);
fprintf(fileout, "%s", buff );
return;
}
sprintf(lbuff, "%5d ", k);
strncpy(buff + pos, lbuff, 7);
for(i=1; i<= preds[k][0]; i ++){
recursive_show_paths(preds, N, preds[k][i], buff, pos + 7, fileout);
}
return;
}
/*
*
* This function calls recursive_show_paths() for each of the nodes of
* the graph, to dump the shortest paths between 'node' and all the
* other nodes of the graph.
*
*/
void show_paths(unsigned int **preds, unsigned int N, FILE *fileout){
int j;
char buff[256];
for (j = 0; j<N; j++){
if (preds[j][0] > 0)
recursive_show_paths(preds, N, j, buff, 0, fileout);
}
}
int main(int argc, char *argv[]){
unsigned int *J_slap=NULL, *r_slap=NULL;
unsigned int K, N, i;
unsigned int **preds, *dists=NULL;
FILE *filein;
if (argc < 3){
usage(argv);
exit(1);
}
if (!strcmp(argv[1], "-")){
/* take the input from STDIN */
filein = stdin;
}
else {
filein = openfile_or_exit(argv[1], "r", 2);
}
read_slap(filein, &K, &N, &J_slap, &r_slap);
i = atoi(argv[2]);
if (i>N){
printf("Node id '%d' does not exist!!!! Exiting....\n", i);
exit(3);
}
fclose(filein);
preds = compute_shortest_paths(N, J_slap, r_slap, i, &dists);
dump_dists(dists, N);
/* check if we should dump the shortest paths on stderr */
if (argc > 3 && !strcmp(argv[3], "SHOW")){
show_paths(preds, N, stderr);
}
/* Cleanup */
for (i=0; i<N; i++){
free(preds[i]);
}
free(preds);
free(dists);
free(J_slap);
free(r_slap);
}
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