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#include "structures/heap.h"
#include <stdlib.h>
#include <string.h>
#include "utils/memory.h"
Heap *heap_new(size_t element_size, int (*compare)(void *element1, void *element2), void (*element_cleanup)(void *element)) {
Heap *heap = safe_malloc(sizeof(Heap));
heap->data = safe_malloc(INIT_HEAP_CAPACITY * sizeof(void *));
heap->n_elements = 0;
heap->element_size = element_size;
heap->capacity = INIT_HEAP_CAPACITY;
heap->compare = compare;
heap->element_cleanup = element_cleanup;
return heap;
}
// return index of parent in heap
size_t parent(size_t i) {
return (i - 1) / 2;
}
// return index of left child in heap
size_t left(size_t i) {
return 2 * i + 1;
}
// return index of right child in heap
size_t right(size_t i) {
return 2 * i + 2;
}
// swap two elements
void swap(void **p_el1, void **p_el2) {
void *tmp = *p_el1;
*p_el1 = *p_el2;
*p_el2 = tmp;
}
// expand heap exponentially to fit el_count elements
void expand_heap(Heap *heap, size_t el_count) {
while (heap->capacity < el_count)
heap->capacity = (heap->capacity << 1) | 1;
heap->data = safe_realloc(heap->data, heap->capacity * sizeof(void *));
}
void heap_insert(Heap *heap, void *element) {
// expand heap if capacity is too small
if (heap->n_elements >= heap->capacity)
expand_heap(heap, heap->n_elements + 1);
// insert into the last position
size_t i = heap->n_elements;
heap->data[i] = safe_malloc(heap->element_size);
memcpy(heap->data[i], element, heap->element_size);
heap->n_elements++;
// heapify up
while (i > 0 && heap->compare(heap->data[i], heap->data[parent(i)])) {
swap(&heap->data[i], &heap->data[parent(i)]);
i = parent(i);
}
}
void *heap_top_get(Heap *heap) {
return heap->n_elements <= 0 ? NULL : heap->data[0];
}
void free_heap_element(Heap *heap, size_t index) {
if (heap->element_cleanup)
heap->element_cleanup(heap->data[index]);
free(heap->data[index]);
}
void heap_top_remove(Heap *heap) {
if (heap->n_elements <= 0)
return;
free_heap_element(heap, 0);
// move last element to root
heap->data[0] = heap->data[--heap->n_elements];
// heapify down
size_t i = 0;
int changed;
do {
size_t l = left(i);
size_t r = right(i);
size_t to_be_parent = i;
if (l < heap->n_elements && heap->compare(heap->data[l], heap->data[to_be_parent]))
to_be_parent = l;
if (r < heap->n_elements && heap->compare(heap->data[r], heap->data[to_be_parent]))
to_be_parent = r;
if ((changed = to_be_parent != i)) {
swap(&heap->data[to_be_parent], &heap->data[i]);
i = to_be_parent;
}
} while (changed);
}
void heap_free(Heap *heap) {
if (!heap)
return;
for (size_t i = 0; i < heap->n_elements; i++) {
free_heap_element(heap, i);
}
free(heap->data);
free(heap);
}
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