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graph.c
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graph.c
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/* graph.c
* Ageneric adjacency list graph data type.
*
* by: Steven Skiena
*
* 2015-05-02 19:26
* Altered by James Shi
*/
#include "bool.h"
#include "queue.h"
#include "graph.h"
void initialize_graph(graph *g, bool directed)
{
int i; /* counter */
g->nvertices = 0;
g->nedges = 0;
g->directed = directed;
for (i=0; i<MAXV; ++i) g->degree[i] = 0;
for (i=0; i<MAXV; ++i) g->edges[i] = NULL;
}
void read_graph(graph *g, bool directed)
{
int i;
int m; /* no. of edges */
int x, y; /* vertices x and y */
initialize_graph(g, directed);
printf("input the number of vertices and edges:");
scanf("%d %d", &(g->nvertices), &m);
for (i=0; i<m; ++i) {
printf("input two vertices of an edge:");
scanf("%d %d", &x, &y);
insert_graph(g, x, y, 1, directed); // set the weight to 1 for unweighted graph
}
}
// this function is not exist in Skiena's code
void read_weighted_graph(graph *g, bool directed)
{
int i;
int m; /* no. of edges */
int x, y; /* vertices x and y */
int weight; /* weight of edge (x, y) */
initialize_graph(g, directed);
printf("input the number of vertices and edges:");
scanf("%d %d", &(g->nvertices), &m);
for (i=0; i<m; ++i) {
printf("input two vertices of an edge:");
scanf("%d %d %d", &x, &y, &weight);
insert_graph(g, x, y, weight, directed);
}
}
void insert_graph(graph *g, int x, int y, int weight, bool directed)
{
edgenode *p; /* temperary pointer */
p = malloc(sizeof(edgenode));
p->weight = weight;
p->y = y;
p->next = g->edges[x];
g->edges[x] = p;
g->degree[x] ++;
if (directed == FALSE)
insert_graph(g, y, x, weight, TRUE);
else
g->nedges++;
}
void delete_graph(graph *g, int x, int y, bool directed)
{
int i; /* counter */
edgenode *p, *p_back; /* temporary pointers */
p = g->edges[x];
p_back = NULL;
while (p != NULL) {
if (p->y == y) {
g->degree[x] --;
if (p_back != NULL)
p_back->next = p->next;
else
g->edges[x] = p->next;
free (p);
if (directed == FALSE)
delete_graph(g, y, x, TRUE);
else
g->nedges --;
return ;
} else {
p = p->next;
}
}
printf("Warning: deletion(%d,%d) not found in g.\n", x, y);
}
void print_graph(graph *g)
{
int i;
edgenode *p;
for (i=1; i<=g->nvertices; ++i) {
printf("%d: ", i);
p = g->edges[i];
while (p != NULL) {
printf(" %d", p->y);
p = p->next;
}
printf("\n");
}
}
void print_weighted_graph(graph *g)
{
int i;
edgenode *p;
for (i=1; i<=g->nvertices; ++i) {
printf("node %d:\n", i);
p = g->edges[i];
while (p != NULL) {
printf("\t (%d, %d):%d\n", i, p->y, p->weight);
p = p->next;
}
printf("\n");
}
}
void find_path(int start, int end, int parents[])
{
if ((start == end) || (end == -1)) {
printf("%d\n", start);
} else {
find_path(start, parents[end], parents);
printf(" %d", end);
}
}