// Dijkstra's algorithm: Compute the distance from a vertex
// This algorithm uses a priority queue (ordered by min distance)
// Returns 0 on success, negative value on error
int graph_shortest_path_from(graph_t* self, vertex_id_t from) {
b_heap_t* heap;
vertex_id_t current_id;
vertex_t* current_vertex;
adjacent_t* current_adjacent;
size_t distance = 0;
if (from >= self->size)
return -1;
heap = b_heap_new();
if (!heap)
return -1;
graph_recompute(self,
GRAPH_RECOMPUTE_REACHED_BIT | GRAPH_RECOMPUTE_DISTANCE_BIT);
self->v[from]->distance = 0;
// The heap initially contains just the first vertex, with a distance 0
// NOTE: The &from is because we must store pointers
printf("Pre-insert\n");
b_heap_insert(heap, &from, 0);
while (!b_heap_empty(heap)) {
printf("Pre-scan\n");
current_id = *((vertex_id_t*)b_heap_front(heap));
printf("Scanning: %zu\n", current_id);
b_heap_pop(heap);
current_vertex = self->v[current_id];
current_adjacent = current_vertex->adjacents_head;
if (current_vertex->reached)
continue;
current_vertex->reached = 1;
// Check all the neighbors, calculate distance to them
while (current_adjacent) {
distance = current_vertex->distance + current_adjacent->weight;
// If found a shorter path, add them to the queue
// Note that at this point an element can be multiple times in
// the queue, but since it's inserted with different priority
// the node will be processed at the correct time
if (self->v[current_adjacent->id]->distance > distance) {
self->v[current_adjacent->id]->distance = distance;
self->v[current_adjacent->id]->reached_from = current_id;
b_heap_insert(heap, &(current_adjacent->id), distance);
}
current_adjacent = current_adjacent->next;
}
}
b_heap_destroy(heap);
return 0;
}
b_heap_t* adjacents_binary_heap(graph_t* self) {
b_heap_t* ret = b_heap_new();
size_t i;
adjacent_t* current;
for (i = 0; i < self->size; ++i) {
current = self->v[i]->adjacents_head;
while (current) {
b_heap_insert(
ret, adjacent_auxiliar_new(i, current->id, current->weight),
current->weight);
current = current->next;
}
}
return ret;
}
int main()
{
b_heap *H=NULL,*x,*min;
int n,i;
printf("\nenter the no of elements to be inserted in heap..\n");
scanf("%d",&n);
for(i=0;i<n;i++)
{
x=(b_heap *)malloc(sizeof(b_heap));
printf("\n enter the value of key.. ");
scanf("%d",&x->key);
H=b_heap_insert(H,x);
printf("\n traversal of heap is... ");
b_heap_traverse(H);
printf("\n");
}
//printf("find the minimum key...\n");
min=b_heap_min(H);
printf("\n minimum key value is: %d",min->key);
getch();
}