private BinarySearchTreeNode <T> FindNodeAndParent(T value, out BinarySearchTreeNode <T> parent)
{
if (_count == 0)
{
throw new InvalidOperationException("Binary Search Tree is empty!");
}
parent = null;
BinarySearchTreeNode <T> pointer = _root;
while (pointer != null)
{
//go to left
if (pointer.CompareTo(value) > 0)
{
parent = pointer;
pointer = pointer.Left;
}
//go to right
else if (pointer.CompareTo(value) < 0)
{
parent = pointer;
pointer = pointer.Right;
}
//match!
else
{
break;
}
}
return(pointer);
}
private void Add(BinarySearchTreeNode <T> node, BinarySearchTreeNode <T> parent)
{
//go to left
if (parent.CompareTo(node.Value) > 0)
{
if (parent.Left == null)
{
parent.Left = node;
}
else
{
Add(node, parent.Left);
}
}
//go to right
else
{
if (parent.Right == null)
{
parent.Right = node;
}
else
{
Add(node, parent.Right);
}
}
}
/// <summary>
/// Removes a node by specifying its value.
/// </summary>
/// <param name="value">Any generic type that implements IComparable of T interface.</param>
/// <returns>True if deleted. Otherwise false.</returns>
/// <exception cref="InvalidOperationException">Binary Search Tree is empty.</exception>
public bool Remove(T value)
{
if (_count == 0)
{
throw new InvalidOperationException("Binary Search Tree is empty!");
}
BinarySearchTreeNode <T> parent = null;
BinarySearchTreeNode <T> node = FindNodeAndParent(value, out parent);
if (node == null)
{
return(false);
}
//decrement first!
_count--;
if (node.Right == null)
{
//it's a root!!
if (parent == null)
{
_root = node.Left;
}
else
{
//it's left
if (parent.CompareTo(value) > 0)
{
parent.Left = node.Left;
}
else
{
parent.Right = node.Left;
}
}
}
else if (node.Right.Left == null)
{
node.Right.Left = node.Left;
if (parent == null)
{
_root = node.Right;
}
else
{
if (parent.CompareTo(value) > 0)
{
parent.Left = node.Right;
}
else
{
parent.Right = node.Right;
}
}
}
else
{
BinarySearchTreeNode <T> parentLeftEnd = node.Right;
BinarySearchTreeNode <T> leftEnd = node.Right.Left;
while (leftEnd.Left != null)
{
parentLeftEnd = leftEnd;
leftEnd = leftEnd.Left;
}
parentLeftEnd.Left = leftEnd.Right;
leftEnd.Left = node.Left;
leftEnd.Right = node.Right;
if (parent == null)
{
_root = leftEnd;
}
else
{
if (parent.CompareTo(value) > 0)
{
parent.Left = leftEnd;
}
else
{
parent.Right = leftEnd;
}
}
}
node = null;
return(true);
}