// this code is used from project 6
MinHeap extractMin(MinHeap *heap){
if(heapsize == 0) return NULL;
int index=0;
MinHeap n = malloc(sizeof(MinHeap));
int a;
n = heap[0];
heapsize--;
for (a=1; a<=heapsize ;a++) {
if(heap[a]->value < n->value){
n = heap[a]; // find the small node
index = a;
}
}
heap[0] = heap[heapsize];
// change node with its new position
position[heap[0]->id]=heapsize;
position[heap[heapsize]->id]=0;
Min_Heapify(heap, 0); // call min heapify function with parent node (0)
return n;
}
void Min_Heapify(LinkedList *s, int i)
{
int leftChild = 2 * i, rightChild = 2 * i + 1, min = -1;
if (leftChild <= s->GetLength&&s->GetPointData(leftChild) < s->GetPointData(i))
min = leftChild;
else
{
min = i;
}
if (rightChild <= s->GetLength&&s->GetPointData(rightChild) < s->GetPointData(min))
{
min = rightChild;
}
if (min != i)
{
//交换s->GetPointData(i)和s->GetPointData(min)
Min_Heapify(s,min);
}
}
// this code is used from project 3
void Min_Heapify(MinHeap *heap, int id){ // sort sub trees to decide parent by exchanging leaf and root
int l = Left(id);
int r = Right(id);
int smallest;
if(l <= heapsize && heap[l]->value < heap[id]->value){
smallest = l;
}else{
smallest = id;
}
if(r <= heapsize && heap[r]->value < heap[smallest]->value){
smallest = r;
}
if(smallest != id){ // decide smallest one and exchange with leaf
position[heap[smallest]->id] = id;
position[heap[id]->id] = smallest;
MinHeap temp = heap[id]; heap[id] = heap[smallest]; heap[smallest] = temp;
Min_Heapify(heap, smallest);
}
}
