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#include <string.h>
#include "priorityqueue.h"
#include "internal.h"
#define START_CAPA 127
PriorityQueue *pq_new(int capa, lt_ft less_than, free_ft free_elem)
{
PriorityQueue *pq = ALLOC(PriorityQueue);
pq->size = 0;
pq->capa = capa;
pq->mem_capa = (START_CAPA > capa ? capa : START_CAPA) + 1;
pq->heap = ALLOC_N(void *, pq->mem_capa);
pq->less_than_i = less_than;
/* need to set this yourself if you want to change it */
pq->free_elem_i = free_elem ? free_elem : &dummy_free;
return pq;
}
PriorityQueue *pq_clone(PriorityQueue *pq)
{
PriorityQueue *new_pq = ALLOC(PriorityQueue);
memcpy(new_pq, pq, sizeof(PriorityQueue));
new_pq->heap = ALLOC_N(void *, new_pq->mem_capa);
memcpy(new_pq->heap, pq->heap, sizeof(void *) * (new_pq->size + 1));
return new_pq;
}
void pq_clear(PriorityQueue *pq)
{
int i;
for (i = 1; i <= pq->size; i++) {
pq->free_elem_i(pq->heap[i]);
pq->heap[i] = NULL;
}
pq->size = 0;
}
void pq_free(PriorityQueue *pq)
{
free(pq->heap);
free(pq);
}
void pq_destroy(PriorityQueue *pq)
{
pq_clear(pq);
pq_free(pq);
}
/**
* This method is used internally by pq_push. It is similar to pq_down except
* that where pq_down reorders the elements from the top, pq_up reorders from
* the bottom.
*
* @param pq the PriorityQueue to reorder
*/
static void pq_up(PriorityQueue *pq)
{
void **heap = pq->heap;
void *node;
int i = pq->size;
int j = i >> 1;
node = heap[i];
while ((j > 0) && pq->less_than_i(node, heap[j])) {
heap[i] = heap[j];
i = j;
j = j >> 1;
}
heap[i] = node;
}
void pq_down(PriorityQueue *pq)
{
register int i = 1;
register int j = 2; /* i << 1; */
register int k = 3; /* j + 1; */
register int size = pq->size;
void **heap = pq->heap;
void *node = heap[i]; /* save top node */
if ((k <= size) && (pq->less_than_i(heap[k], heap[j]))) {
j = k;
}
while ((j <= size) && pq->less_than_i(heap[j], node)) {
heap[i] = heap[j]; /* shift up child */
i = j;
j = i << 1;
k = j + 1;
if ((k <= size) && pq->less_than_i(heap[k], heap[j])) {
j = k;
}
}
heap[i] = node;
}
void pq_push(PriorityQueue *pq, void *elem)
{
pq->size++;
if (pq->size >= pq->mem_capa) {
pq->mem_capa <<= 1;
REALLOC_N(pq->heap, void *, pq->mem_capa);
}
pq->heap[pq->size] = elem;
pq_up(pq);
}
PriorityQueueInsertEnum pq_insert(PriorityQueue *pq,
void *elem)
{
if (pq->size < pq->capa) {
pq_push(pq, elem);
return PQ_ADDED;
}
if (pq->size > 0 && pq->less_than_i(pq->heap[1], elem)) {
pq->free_elem_i(pq->heap[1]);
pq->heap[1] = elem;
pq_down(pq);
return PQ_INSERTED;
}
pq->free_elem_i(elem);
return PQ_DROPPED;
}
void *pq_top(PriorityQueue *pq)
{
return pq->size ? pq->heap[1] : NULL;
}
void *pq_pop(PriorityQueue *pq)
{
if (pq->size > 0) {
void *result = pq->heap[1]; /* save first value */
pq->heap[1] = pq->heap[pq->size]; /* move last to first */
pq->heap[pq->size] = NULL;
pq->size--;
pq_down(pq); /* adjust heap */
return result;
}
return NULL;
}
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