/// <summary>
/// Time complexity: O(log(n)).
/// </summary>
public T Extract()
{
if (heapForest.Head == null)
{
throw new Exception("Empty heap");
}
var minMaxTree = heapForest.Head;
var current = heapForest.Head;
//find minMaximum tree
while (current.Next != null)
{
current = current.Next;
if (comparer.Compare(minMaxTree.Data.Value, current.Data.Value) > 0)
{
minMaxTree = current;
}
}
//remove tree root
heapForest.Delete(minMaxTree);
var newHeapForest = new DoublyLinkedList <BinomialHeapNode <T> >();
//add removed roots children as new trees to forest
foreach (var child in minMaxTree.Data.Children)
{
child.Parent = null;
newHeapForest.InsertLast(child);
}
mergeSortedForests(newHeapForest);
meld();
removeMapping(minMaxTree.Data.Value, minMaxTree.Data);
Count--;
return(minMaxTree.Data.Value);
}
/// <summary>
/// Merge roots with same degrees in Forest
/// </summary>
private void Meld()
{
if (heapForest.Head == null)
{
return;
}
var cur = heapForest.Head;
var next = heapForest.Head.Next;
//TODO
while (next != null)
{
//case 1
//degrees are differant
//we are good to move ahead
if (cur.Data.Degree != next.Data.Degree)
{
cur = next;
next = cur.Next;
}
//degress of cur & next are same
else
{
//case 2 next degree equals next-next degree
if (next.Next != null &&
cur.Data.Degree == next.Next.Data.Degree)
{
cur = next;
next = cur.Next;
continue;
}
//case 3 cur value is less than next
if (cur.Data.Value.CompareTo(next.Data.Value) >= 0)
{
//add next as child of current
cur.Data.Children.Add(next.Data);
next.Data.Parent = cur.Data;
heapForest.Delete(next);
next = cur.Next;
continue;
}
//case 4 cur value is greater than next
if (cur.Data.Value.CompareTo(next.Data.Value) >= 0)
{
continue;
}
//add current as child of next
next.Data.Children.Add(cur.Data);
cur.Data.Parent = next.Data;
heapForest.Delete(cur);
cur = next;
next = cur.Next;
}
}
}