/// <summary>
/// Removes all the empty levels leftover in the Skip List
/// </summary>
protected void clearEmptyLevels()
{
if (this.levels > 1) //more than one level, don't want to remove bottom level
{
SkipListNode <T> currentNode = this.topLeft;
while (currentNode != this.bottomLeft) //do not remove the bottom level
{
if (currentNode.IsHeader() && currentNode.Next.IsFooter())
{
SkipListNode <T> belowNode = currentNode.Below;
//Remove the empty level
//Update pointers
topLeft = currentNode.Below;
//Remove links
currentNode.Next.Dispose();
currentNode.Dispose();
//Update counters
this.levels--;
currentNode = belowNode; //scan down
}
else
{
break; //a single non-emtpy level means the rest of the levels are not empty
}
}
}
}
/// <summary>
/// Removes a value or node from the Skip List
/// </summary>
public virtual bool Remove(SkipListNode <T> valueNode)
{
if (valueNode == null)
{
return(false);
}
else
{
//Make sure node is top-level node in it's tower
if (valueNode.Above != null)
{
valueNode = this.FindHighest(valueNode);
}
//---Delete nodes going down the tower
SkipListNode <T> currentNodeDown = valueNode;
while (currentNodeDown != null)
{
//Remove right-left links
SkipListNode <T> previousNode = currentNodeDown.Previous;
SkipListNode <T> nextNode = currentNodeDown.Next;
//Link the previous and next nodes to each other
previousNode.Next = nextNode;
nextNode.Previous = previousNode;
SkipListNode <T> belowNode = currentNodeDown.Below; //scan down
currentNodeDown.Dispose(); //unlink previous
currentNodeDown = belowNode;
}
//update counter
this.size--;
//Clean up the Skip List by removing levels that are now empty
this.clearEmptyLevels();
return(true);
}
}