/// <summary>
/// This Function is for Recursive Deletion.
/// </summary>
/// <param name="current">Current node</param>
/// <param name="key">Key</param>
/// <returns>Avl Node</returns>
private AVLNode <TKey, TValue> RecursiveRemove(AVLNode <TKey, TValue> current, TKey key)
{
AVLNode <TKey, TValue> parent;
if (current == null)
{
return(null);
}
else
{
// Left subtree.
if (key.CompareTo(current.Key) < 0)
{
current.LeftNode = RecursiveRemove(current.LeftNode, key);
if (BalanceFactor(current) == -2)//here
{
if (BalanceFactor(current.RightNode) <= 0)
{
current = RotateRight(current);
}
else
{
current = DoubleRight(current);
}
}
}
// Right subtree
else if (key.CompareTo(current.Key) > 0)
{
current.RightNode = RecursiveRemove(current.RightNode, key);
if (BalanceFactor(current) == 2)
{
if (BalanceFactor(current.LeftNode) >= 0)
{
current = RotateLeft(current);
}
else
{
current = DoubleLeft(current);
}
}
}
// When target is found.
else
{
if (current.RightNode != null)
{
// Deleting its inorder successor.
parent = current.RightNode;
while (parent.LeftNode != null)
{
parent = parent.LeftNode;
}
current.Key = parent.Key;
current.RightNode = RecursiveRemove(current.RightNode, parent.Key);
// Rebalancing.
if (BalanceFactor(current) == 2)
{
if (BalanceFactor(current.LeftNode) >= 0)
{
current = RotateLeft(current);
}
else
{
current = DoubleLeft(current);
}
}
}
// When current.left != null.
else
{
return(current.LeftNode);
}
}
}
return(current);
}