void slide_down(const vertex &v, const T &value)
{
/* Jeżeli jesteśmy w liściu to nie ma gdzie zjeżdzać. */
if (lchild(v) > n) {
array[v] = value;
return;
}
/* Jeżeli wierzchołek ma jednego syna to sprawa dosyć prosta. */
if (lchild(v) == n) {
if (value < array[lchild(v)]) {
array[v] = value;
} else {
array[v] = array[lchild(v)];
array[lchild(v)] = value;
}
return;
}
/* Jeżeli ma obu synów to sprawdzamy czy mniejszy zaburzy porządek. */
vertex m = array[lchild(v)] < array[rchild(v)] ? lchild(v) : rchild(v);
if (value > array[m]) {
array[v] = array[m];
slide_down(m, value);
} else {
array[v] = value;
}
}
/* Remove number from heap
Unspecified behavior if heap is empty
*/
int removeHeap(heap *aHeap) {
assert(aHeap != NULL);
assert(aHeap->size > 0);
aHeap->size--;
int retVal = aHeap->array[0];
aHeap->array[0] = aHeap->array[aHeap->size];
// Trickle down
int position = 0;
while (true) {
int left = lchild(position);
int right = rchild(position);
int largest = position;
if (left < aHeap->size && aHeap->array[left] > aHeap->array[largest]) {
largest = left;
}
if (right < aHeap->size && aHeap->array[right] > aHeap->array[largest]) {
largest = right;
}
if (largest == position) {
break;
} else {
int tmp = aHeap->array[position];
aHeap->array[position] = aHeap->array[largest];
aHeap->array[largest] = tmp;
position = largest;
}
}
return retVal;
}
/* 维持堆中以root为根的子堆的堆性质 */
static void heapify(int *heap, int root, int size, fun compare)
{
int left = lchild(root);
int right = rchild(root);
int most = root; /* 根、左子结点、右子结点中最大(大顶堆)或最小(小顶堆)的结点 */
if (left < size) /* 求出根、左子结点、右子结点中最大(大顶堆)或最小(小顶堆)的结点 */
most = !compare(heap[left], heap[most])? left: most;
if (right < size)
most = !compare(heap[right], heap[most])? right: most;
if (most != root) {
/* 最大/最小的结点应该在根上 */
swap(heap + most, heap + root);
/* 若有变动，则应对most为根的子堆也进行堆性质维护 */
heapify(heap, most, size, compare);
}
}
