Actually i was working towards BFS alog, then I came across this code for BFS.

It works fine and gives correct results.

I wanted to modify it but i dont follow the whole code.

I dont need the path for the traversal path but just wanna know if a particular is connected to the some other particular node(say if 1 is connected to 5 or so).

But i dont where i shd modify.....

the code is

Code:

# include <stdio.h>
# define size 20
# define T 1
# define F 0
struct Edge
{
int terminal;
struct Edge *next;
};
struct Vertex
{
int visit;
int vertex_no;
char info;
int path_length;
struct Edge *Edge_Ptr;
};
struct Q
{
int info;
struct Q *next;
};
void Table(int , int matrix [size][size], struct Vertex vert[size]);
struct Edge *Insert_Vertex (int , struct Edge *);
void BFS ( int , struct Vertex vert [size]);
void Input(int, int mat [size][size]);
void Output(int number, int mat [size][size]);
struct Q *Insert_Queue(int vertex_no, struct Q *first);
struct Q *Delete_Queue(int *vertex_no, struct Q *first);
/* Insert vertex into connectivity list */
struct Edge * Insert_Vertex (int vertex_no, struct Edge*first) {
struct Edge *new1, *current;
new1 = (struct Edge *) malloc(sizeof(struct Edge));
new1->terminal = vertex_no;
new1->next = NULL;
if (!first)
return (new1);
for (current = first; current->next; current = current->next);
current->next = new1;
return (first);
}
/* Insert vertices into queue */
struct Q * Insert_Queue(int vertex_no, struct Q *first)
{
struct Q *new1, *current;
new1 =(struct Q *) malloc(sizeof(struct Q));
new1->info = vertex_no;
new1->next = NULL;
if (!first)
return (new1);
for (current = first; current->next; current = current->next);
current->next = new1;
return (first);
}
struct Q * Delete_Queue(int *vertex_no, struct Q *first)
{
struct Q *previous;
if (!first)
return (NULL);
*vertex_no = first->info;
previous = first;
first = first->next;
free(previous);
return (first);
}
/* Initializing entries */
void Table(int vertex_num, int matrix [size][size],struct Vertex vert[size])
{
int i, j;
for (i = 0; i < vertex_num; i++)
{
vert [i].visit = F;
vert [i].vertex_no = i+1;
vert [i].info = 'A'+ i;
vert [i].path_length = 0;
vert [i].Edge_Ptr = NULL;
}
for (i =0; i < vertex_num ; i++)
for (j =0; j < vertex_num ; j++)
if (matrix [i][j] > 0 )
vert [i].Edge_Ptr = Insert_Vertex (j, vert [i].Edge_Ptr);
}
/* Computing path length */
void BFS ( int index, struct Vertex vert [size])
{
struct Q *queue = NULL;
struct Edge *Link;
vert [index].visit = T;
queue = Insert_Queue(index, queue);
while(queue)
{
queue = Delete_Queue(&index, queue);
for ( Link = vert [index].Edge_Ptr; Link; Link = Link->next)
{
if (vert [Link->terminal].visit == F)
{
vert[Link->terminal].visit = T;
vert[Link->terminal].path_length=vert[index].path_length+1;
queue = Insert_Queue(Link->terminal, queue);
}
}
}
}
/* Input function to read adjacency matrix */
void Input(int number, int mat [size][size])
{
int i, j;
printf("\n Input the adjacency matrix \n");
for (i =0; i < number; i++)
{
for (j=0; j < number; j ++)
{
scanf("%d", &mat [i][j]);
}
printf("\n");
}
}
/* Output function to display adjacency matrix */
void Output(int number, int mat [size][size])
{
int i, j;
printf("\n Adjacency matrix \n");
for (i =0; i < number; i++)
{
for (j=0; j < number; j ++)
{
printf(" %d", mat [i][j]);
}
printf("\n");
}
}
/* Function main */
int main()
{
int i, number, index;
int mat [size][size];
struct Vertex vert [size];
struct Edge *List;
printf("\n Input the number of vertices in the graph: ");
scanf("%d", &number);
Input(number, mat);
Output(number, mat);
Table(number, mat, vert);
printf("\n Input the starting vertex 0- %d :",number-1);
scanf("%d", &index);
BFS (index, vert);
printf("\n Path length of the vertex from %c", vert[index].info)
;
printf("\n Vertex Length Vertex Connectivity \n ");
for (i = 0; i < number; i++)
{
printf("\n %c %d ",vert[i].info, vert[i].path_length);
for (List= vert[i].Edge_Ptr; List; List = List->next)
{
printf(" ");
putchar(List->terminal+'A');
}
}
}

thanks.