/**
* Shortest Path solution implemented using the Dijkstra algorithm
*/
int dijkstra(Graph *graph, int source, pri_queue priq,
Energy *distance, int previous[], Energy shortest_distance)
{
int vertex, adjacent, v;
Energy alt;
int *visited = calloc(graph->list_size, sizeof(int));
for(v = 0; v < graph->list_size; distance[v++] = ENERGY_MAX);
previous[source] = NONE;
distance[source] = graph->vertexes[source].pixel->energy;
visited[source] = 1;
priq_purge(priq);
priq_push(priq, source, distance[source]);
int dest = NONE;
while(priq_size(priq))
{
vertex = priq_pop(priq);
v = 0;
adjacent = graph->vertexes[vertex].adj[v++];
if(adjacent == NONE)
{
dest = vertex;
break;
}
#ifdef OPT_GRAPH_SHORTEST_PATH_BREAK
else
if (distance[vertex] >= shortest_distance)
{
dest = BREAK;
break;
}
#endif
do
{
if(adjacent >= 0 && !visited[adjacent])
{
alt = distance[vertex] +
graph->vertexes[adjacent].pixel->energy;
if(alt < distance[adjacent])
{
distance[adjacent] = alt;
previous[adjacent] = vertex;
priq_push(priq, adjacent, alt);
}
}
adjacent = graph->vertexes[vertex].adj[v++];
} while(adjacent != NONE);
visited[vertex] = 1;
}
free(visited);
return dest;
}
int main()
{
int i, p;
const char *c, *tasks[] ={
"Clear drains", "Feed cat", "Make tea", "Solve RC tasks", "Tax return" };
int pri[] = { 3, 4, 5, 1, 2 };
/* make two queues */
pri_queue q = priq_new(0), q2 = priq_new(0);
/* push all 5 tasks into q */
for (i = 0; i < 5; i++)
priq_push(q, tasks[i], pri[i]);
/* pop them and print one by one */
while ((c = priq_pop(q, &p)))
printf("%d: %s\n", p, c);
/* put a million random tasks in each queue */
for (i = 0; i < 1 << 20; i++) {
p = rand() / ( RAND_MAX / 5 );
priq_push(q, tasks[p], pri[p]);
p = rand() / ( RAND_MAX / 5 );
priq_push(q2, tasks[p], pri[p]);
}
printf("\nq has %d items, q2 has %d items\n", priq_size(q), priq_size(q2));
/* merge q2 into q; q2 is empty */
priq_combine(q, q2);
printf("After merge, q has %d items, q2 has %d items\n",
priq_size(q), priq_size(q2));
/* pop q until it's empty */
for (i = 0; (c = priq_pop(q, 0)); i++);
printf("Popped %d items out of q\n", i);
return 0;
}
/**
* Priority queue invariant check.
* Complexity always O(2n)
* @return If NULL -> Ok. Else an error msg.
*/
const char* priq_invariant(Priq q)
{
if(!q)
return "NULL POINTER EXCEP: Pcue base struct undefinded";
if(!q->cmp)
return "NULL POINTER EXCEP: Pcue compare function undefinded";
if(!q->top && priq_size(q) != 0)
return "WRONG STRUCTURE: top = NULL but size > 0";
if(q->top && priq_size(q) == 0)
return "WRONG STRUCTURE: top != NULL but size = 0";
if(!_priq_heap_inv(q->top, q->cmp))
return "WRONG STRUCTURE: heap invariant failed";
if(q->size != _priq_count_contend(q->top))
return "WRONG STRUCTURE: size != real #contend";
return NULL;
}
