/// <summary>
/// delete node from parent
/// </summary>
/// <param name="node"></param>
private void DeleteChild(PairingHeapNode <T> node)
{
//if this node is the child head pointer of parent
if (node.IsHeadChild)
{
var parent = node.Previous;
//use close sibling as new parent child pointer
if (node.Next != null)
{
node.Next.Previous = parent;
}
parent.ChildrenHead = node.Next;
}
else
{
//just do regular deletion from linked list
node.Previous.Next = node.Next;
if (node.Next != null)
{
node.Next.Previous = node.Previous;
}
}
}
/// <summary>
/// makes the smaller node parent of other and returns the Parent
/// </summary>
/// <param name="node1"></param>
/// <param name="node2"></param>
private PairingHeapNode <T> Meld(PairingHeapNode <T> node1,
PairingHeapNode <T> node2)
{
if (node2 != null)
{
node2.Previous = null;
node2.Next = null;
}
if (node1 == null)
{
return(node2);
}
node1.Previous = null;
node1.Next = null;
if (node1.Value.CompareTo(node2.Value) <= 0)
{
AddChild(ref node1, node2);
return(node1);
}
else
{
AddChild(ref node2, node1);
return(node2);
}
}
/// <summary>
/// O(n), Amortized O(log(n))
/// Melds all the nodes to one single Root Node
/// </summary>
/// <param name="headNode"></param>
private void Meld(PairingHeapNode <T> headNode)
{
if (headNode == null)
{
return;
}
var passOneResult = new List <PairingHeapNode <T> >();
var current = headNode;
if (current.Next == null)
{
headNode.Next = null;
headNode.Previous = null;
passOneResult.Add(headNode);
}
else
{
while (true)
{
if (current == null)
{
break;
}
if (current.Next != null)
{
var next = current.Next;
var nextNext = next.Next;
passOneResult.Add(Meld(current, next));
current = nextNext;
}
else
{
var lastInserted = passOneResult[passOneResult.Count - 1];
passOneResult[passOneResult.Count - 1] = Meld(lastInserted, current);
break;
}
}
}
var passTwoResult = passOneResult[passOneResult.Count - 1];
if (passOneResult.Count == 1)
{
Root = passTwoResult;
return;
}
for (int i = passOneResult.Count - 2; i >= 0; i--)
{
current = passOneResult[i];
passTwoResult = Meld(passTwoResult, current);
}
Root = passTwoResult;
}
/// <summary>
/// Insert a new Node
/// </summary>
/// <param name="newItem"></param>
/// <returns></returns>
public PairingHeapNode <T> Insert(T newItem)
{
var newNode = new PairingHeapNode <T>(newItem);
Root = Meld(Root, newNode);
Count++;
return(newNode);
}
public void Compare_CheckAscending_ReturnPositive()
{
var minHeap = new PairingNodeComparer <int>(Sorting.Descending, Comparer <int> .Default);
var node1 = new PairingHeapNode <int>(10);
var node2 = new PairingHeapNode <int>(20);
var items = minHeap.Compare(node1.Value, node2.Value);
items.Should().Be(1);
}
/// <summary>
/// Update heap after a node value was decremented
/// </summary>
/// <param name="node"></param>
public void DecrementKey(PairingHeapNode <T> node)
{
if (node == Root)
{
return;
}
DeleteChild(node);
Root = Meld(Root, node);
}
/// <summary>
/// Add new child to parent node
/// </summary>
/// <param name="parent"></param>
/// <param name="child"></param>
private void AddChild(ref PairingHeapNode <T> parent, PairingHeapNode <T> child)
{
if (parent.ChildrenHead == null)
{
parent.ChildrenHead = child;
child.Previous = parent;
return;
}
var head = parent.ChildrenHead;
child.Previous = head;
child.Next = head.Next;
if (head.Next != null)
{
head.Next.Previous = child;
}
head.Next = child;
}
public void PairingHeap()
{
var heap = _pairingHeap;
var heapIndex = _pairingHeapNodes;
var priorities = _priorities;
for (int i = 0; i < Size; i++)
{
PairingHeapNode <int, int> node = heap.Add(priorities[i], i);
heapIndex[i] = node;
}
for (int i = 0; i < Size; i++)
{
heap.Update(heapIndex[i], -priorities[i]);
}
while (heap.Count > 0)
{
heap.Pop();
}
}
/// <summary>
/// Merge another heap with this heap
/// </summary>
/// <param name="PairingHeap"></param>
public void Merge(PairingMinHeap <T> PairingHeap)
{
Root = Meld(Root, PairingHeap.Root);
Count = Count + PairingHeap.Count;
}