//
// Swaps two nodes in the array
// Necessary since we need to update the indices of the nodes in the array (for decreaseKey)
//
private void Swap(int index1, int index2)
{
// Swap the nodes
HeapNode <int> temp = heap[index1];
heap[index1] = heap[index2];
heap[index2] = temp;
// Update the array indices
heap[index1].degree = index1;
heap[index2].degree = index2;
}
//
// Makes the given node priority the newKey value and updates the heap
// O(log n)
//
public void DecreaseKey(HeapNode <int> node, int newKey)
{
int index = node.degree;
node.key = newKey;
// Moves the value up the heap until a suitable point is determined
while (index > 0 && heap[ParentIndex(index)].key <= heap[index].key)
{
Swap(index, ParentIndex(index));
index = ParentIndex(index);
}
}
//
// Creates the Max-heap array and places the smallest value possible in array position 0
//
public MaxHeap(int sz)
{
heap = new HeapNode <int> [sz + 5]; // +5 for safety
Count = 0;
//
// Make index 0 a sentinel value
//
HeapNode <int> node = new HeapNode <int>(-1);
node.key = Double.PositiveInfinity;
heap[0] = node;
}
//
// Inserts an element (similar to Insertion; update the heap)
// O(log n)
//
public void Insert(HeapNode <int> node, int key)
{
// Add the node to the last open position
node.key = key;
node.degree = ++Count;
heap[Count] = node;
// Moves the value up the heap until a suitable point is determined
int current = Count;
while (heap[current].key >= heap[ParentIndex(current)].key)
{
Swap(current, ParentIndex(current));
current = ParentIndex(current);
}
}
public int degree; // number of children in Fibonacci Heap; index in the min-heap
public HeapNode(T data)
{
right = this;
left = this;
this.data = data;
}