/// <summary>
/// Deletes the specified item from this heap.
/// </summary>
/// <param name="item">Item to be deleted.</param>
/// <exception cref="InvalidOperationException">
/// This heap is empty.
/// </exception>
public void Delete(IPriorityQueueItem <T> item)
{
if (this.IsEmpty())
{
throw new InvalidOperationException("This heap is empty.");
}
if (item is FibonacciHeapItem <T> )
{
FibonacciHeapItem <T> fibHeapItem = (FibonacciHeapItem <T>)item;
// Cut the edge joining the containing node x to its parent p.
FibonacciHeapNode <T> x = fibHeapItem.ContainingNode;
if (x.Parent == null)
{
// x is originally a root - just remove it from the list of roots.
if (x == this.minimumNode)
{
this.DeleteMin();
return;
}
else
{
x.LeftSibling.RightSibling = x.RightSibling;
x.RightSibling.LeftSibling = x.LeftSibling;
}
}
else
{
/*
* As x is not a root, remove it from the list of children of
* its parent and decrease its parent's rank.
*/
x.CutEdgeToParent(false, this);
/*
* Form a new list of roots by concatenating the list of children of
* x with the original list of roots.
*/
if (x.SomeChild != null)
{
this.minimumNode.RightSibling.LeftSibling = x.SomeChild.LeftSibling;
x.SomeChild.LeftSibling.RightSibling = this.minimumNode.RightSibling;
this.minimumNode.RightSibling = x.SomeChild;
x.SomeChild.LeftSibling = this.minimumNode;
}
}
this.count--;
}
else
{
throw new ArgumentException("Can work only on Fibonacci Heap items.", "item");
}
}
/// <summary>
/// Decreases the key of the specified item in this heap by subtracting
/// the passed non-negative real number <c>delta</c>.
/// </summary>
/// <param name="item">Item to decrease the key of.</param>
/// <param name="delta">Non-negative real number to be subtracted from the item's key.</param>
/// <exception cref="ArgumentOutOfRangeException">
/// <c>delta</c> is negative.
/// </exception>
/// <exception cref="InvalidOperationException">
/// This heap is empty.
/// </exception>
public void DecreaseKey(IPriorityQueueItem <T> item, double delta)
{
if (delta < 0)
{
throw new ArgumentOutOfRangeException("delta", "delta has to be non-negative.");
}
if (this.IsEmpty())
{
throw new InvalidOperationException("This heap is empty.");
}
if (item is FibonacciHeapItem <T> )
{
FibonacciHeapItem <T> fibHeapItem = (FibonacciHeapItem <T>)item;
// Subtract delta from the key of the passed item.
fibHeapItem.Key -= delta;
// Cut the edge joining the containing node x to its parent p.
FibonacciHeapNode <T> x = fibHeapItem.ContainingNode;
if (x.Parent != null)
{
/*
* If x is not a root, remove it from the list of children of
* its parent, decrease its parent's rank, and add it to the list
* of roots of this heap in order to preserve the heap order.
*/
x.CutEdgeToParent(true, this);
}
// Redefine the minimum node of this heap, if necessary.
if (fibHeapItem.Key < this.minimumNode.Item.Key)
{
this.minimumNode = x;
}
}
else
{
throw new ArgumentException("Can only work on Fibonacci Heap items.", "item");
}
}