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Pqueue.cpp
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Pqueue.cpp
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#include <stdlib.h>
#include "pqueue.h"
pqueue_t* pqueue_create(pqueue_size_t capacity)
{
if (capacity <= 0)
capacity = DEFAULT_PQUEUE_SIZE;
pqueue_t* pqueue = (pqueue_t*)malloc(sizeof(*pqueue));
pqueue->container = (element_t*)malloc(sizeof(element_t)*(capacity + 1));
pqueue->capacity = capacity;
pqueue->size = 0;
return pqueue;
}
void pqueue_release(pqueue_t* pqueue)
{
free(pqueue->container);
free(pqueue);
}
#define PQUEUE_ASSIGN_ELEMENT_INDEX(element, index) \
if ((element).index_ptr) \
{ \
*((element).index_ptr) = (index); \
}
#define PQUEUE_COPY_ELEMENT(dest_element, src_element, dest_index) \
(dest_element) = (src_element); \
PQUEUE_ASSIGN_ELEMENT_INDEX((dest_element), (dest_index))
static void pqueue_up_shift(pqueue_t* pqueue, pqueue_size_t index)
{
if (index <= 1) return;
pqueue_size_t i, j;
element_t* container = pqueue->container;
element_t element = container[index];
for (i = index, j = i >> 1; j > 0 && compare_element(element, container[j]); i = j, j >>= 1)
{
PQUEUE_COPY_ELEMENT(container[i], container[j], i);
}
if (i == index) return;
PQUEUE_COPY_ELEMENT(container[i], element, i);
}
static int pqueue_realloc(pqueue_t* pqueue)
{
if (pqueue->capacity >= MAX_PQUEUE_SIZE)
return 0;
pqueue_size_t new_capacity = pqueue->capacity + pqueue->capacity > 2 + 1;
if (new_capacity > MAX_PQUEUE_SIZE)
new_capacity = MAX_PQUEUE_SIZE;
element_t* new_container = (element_t*)realloc(pqueue->container, new_capacity);
if (!new_container)
return 0;
pqueue->container = new_container;
pqueue->capacity = new_capacity;
return 1;
}
int pqueue_push(pqueue_t* pqueue, element_t element)
{
if (pqueue->size >= pqueue->capacity && !pqueue_realloc(pqueue))
return 0;
pqueue->container[++pqueue->size] = element;
PQUEUE_ASSIGN_ELEMENT_INDEX(element, pqueue->size);
pqueue_up_shift(pqueue, pqueue->size);
return 1;
}
static void pqueue_down_shift(pqueue_t* pqueue, pqueue_size_t index)
{
if (index >= pqueue->size) return;
element_t* container = pqueue->container;
element_t element = container[index];
element_t* last_element_ptr = &container[pqueue->size];
pqueue_size_t i, j;
for (i = index, j = i << 1; j <= pqueue->size; i = j, j <<= 1)
{
if (j != pqueue->size && compare_element(container[j + 1], container[j]))
j++;
if (compare_element(container[j], element))
{
if (compare_element(container[j], *last_element_ptr))
{
PQUEUE_COPY_ELEMENT(container[i], container[j], i);
}
else
{
PQUEUE_COPY_ELEMENT(container[i], *last_element_ptr, i);
i = pqueue->size;
break;
}
}
else
{
break;
}
}
if (i == index) return;
PQUEUE_COPY_ELEMENT(container[i], element, i);
}
element_t pqueue_pop(pqueue_t* pqueue)
{
element_t ret = { NULL, (priority_t)0, NULL };
if (pqueue->size == 0)
return ret;
element_t* container = pqueue->container;
element_t first_element = container[1];
element_t* last_element_ptr = &container[pqueue->size--];
pqueue_size_t i, j;
for (i = 1, j = i << 1; j <= pqueue->size; i = j, j <<= 1)
{
if (j != pqueue->size && compare_element(container[j + 1], container[j]))
j++;
if (compare_element(container[j], *last_element_ptr))
{
PQUEUE_COPY_ELEMENT(container[i], container[j], i);
}
else
{
break;
}
}
if (pqueue->size > 0)
{
PQUEUE_COPY_ELEMENT(container[i], *last_element_ptr, i);
}
PQUEUE_ASSIGN_ELEMENT_INDEX(first_element, 0);
return first_element;
}
int pqueue_change_priority(pqueue_t* pqueue, pqueue_size_t index, priority_t new_priority)
{
if (index < 1 || index > pqueue->size)
return 0;
element_t* element_ptr = &pqueue->container[index];
priority_t old_priority = element_ptr->priority;
element_ptr->priority = new_priority;
if (compare_priority(new_priority, old_priority))
pqueue_up_shift(pqueue, index);
else
pqueue_down_shift(pqueue, index);
return 1;
}