public BST()
{
Root = null;
}
public BNode(T value, BNode <T> left, BNode <T> right)
{
base.Value = value;
base.Neighbors = new List <Node <T> >(new[] { left, right });
}
public virtual void Clear()
{
Root = null;
}
public virtual BNode <T> Remove(T value)
{
if (IsEmpty())
{
return(null);
}
BNode <T> current = Root;
int parentDirection = 0;
while (true)
{
int direction = value.CompareTo(current.Value);
if (direction == 0)
{
break;
}
parentDirection = direction;
current = direction < 0 ? current.Left : current.Right;
if (current == null)
{
return(null);
}
}
if (current.Left == null && current.Right == null) // no children
{
if (current.Parent == null) // if root being removed
{
this.Root = null;
}
else // remove reference to current node from parent node
{
if (parentDirection < 0)
{
current.Parent.Left = null;
}
else
{
current.Parent.Right = null;
}
}
}
else if (current.Left != null && current.Right != null) // two children
{
BNode <T> successor = current.Right;
while (successor.Left != null)
{
successor = successor.Left; // find smallest value greater than current value
}
if (successor.Parent.Left == successor)
{
successor.Parent.Left = null; // remove successor from tree
}
else
{
successor.Parent.Right = null; // remove successor from tree
}
// connect parent and successor together
successor.Parent = current.Parent; // attach successor to same parent as current
if (current.Parent == null)
{
this.Root = successor;
}
else
{
if (parentDirection < 0)
{
current.Parent.Left = successor;
}
else
{
current.Parent.Right = successor;
}
}
// connect successor to children of removed node
successor.Left = current.Left;
successor.Right = current.Right;
if (current.Left != null)
{
current.Left.Parent = successor;
}
if (current.Right != null)
{
current.Right.Parent = successor;
}
}
else // one child
{
if (current.Parent == null)
{
this.Root = current.Left == null ? current.Left : current.Right;
}
else
{
BNode <T> successor = current.Right ?? current.Left;
// connect parent to successor
if (parentDirection > 0)
{
current.Parent.Right = successor;
}
else
{
current.Parent.Left = successor;
}
// connect successor to parent
successor.Parent = current.Parent;
}
}
return(current);
}
private BST(BNode <T> root)
{
this.Root = root;
}
