/// <summary>
/// Initializes a new instance of the <see cref="AVLTree{T}"/> class.
/// Basic constructor.
/// </summary>
public AVLTree()
{
this._root = null;
}
/// <summary>
/// Clears nodes of the tree.
/// </summary>
public override void Clear()
{
this._root = null;
}
/// <summary>
/// Removes element from the tree.
/// </summary>
/// <param name="data">
/// Element to be removed.
/// </param>
/// <returns>
/// The remove.
/// </returns>
public override bool Remove(T data)
{
if (this._root == null)
{
return(false);
}
AVLTreeNode <T> current = this._root, parent = null;
int result = this._comparer.Compare(current.Values[0], data);
while (result != 0)
{
if (result > 0)
{
parent = current;
current = current.Left;
}
else
{
parent = current;
current = current.Right;
}
if (current == null)
{
return(false);
}
result = this._comparer.Compare(current.Values[0], data);
}
if (current.Right == null)
{
if (parent == null)
{
if (current.Left != null)
{
current.Left.Parent = parent;
}
this._root = current.Left;
}
else
{
result = this._comparer.Compare(parent.Values[0], current.Values[0]);
if (result > 0)
{
if (current.Left != null)
{
current.Left.Parent = parent;
}
parent.Left = current.Left;
}
else
{
if (current.Right != null)
{
current.Right.Parent = parent;
}
parent.Right = current.Right;
}
}
}
else if (current.Right.Left == null)
{
current.Right.Left = current.Left;
if (current.Left != null)
{
current.Left.Parent = current.Right;
}
if (parent == null)
{
if (current.Right != null)
{
current.Right.Parent = parent;
}
this._root = current.Right;
}
else
{
result = this._comparer.Compare(parent.Values[0], current.Values[0]);
if (result > 0)
{
if (current.Right != null)
{
current.Right.Parent = parent;
}
parent.Left = current.Right;
}
else
{
if (current.Right != null)
{
current.Right.Parent = parent;
}
parent.Right = current.Right;
}
}
}
else
{
AVLTreeNode <T> leftMost = current.Right, lmParent = current;
while (leftMost.Left != null)
{
lmParent = leftMost;
leftMost = lmParent.Left;
}
lmParent.Left = leftMost.Right;
leftMost.Left = current.Left;
leftMost.Right = current.Right;
if (lmParent.Left != null)
{
lmParent.Left.Parent = leftMost;
}
if (leftMost.Right != null)
{
leftMost.Right.Parent = lmParent;
}
if (current.Left != null)
{
current.Left.Parent = leftMost;
}
if (current.Right != null)
{
current.Right.Parent = leftMost;
}
if (parent == null)
{
leftMost.Parent = parent;
this._root = leftMost;
}
else
{
result = this._comparer.Compare(parent.Values[0], current.Values[0]);
if (result > 0)
{
leftMost.Parent = parent;
parent.Left = leftMost;
}
else
{
leftMost.Parent = parent;
parent.Right = leftMost;
}
}
}
current.Parent = current.Left = current.Right = null;
if (this._root != null)
{
while (this._root.Parent != null)
{
this._root = (AVLTreeNode <T>) this._root.Parent;
}
this._root.UpdateHeight();
this._root.Balance();
while (this._root.Parent != null)
{
this._root = (AVLTreeNode <T>) this._root.Parent;
}
}
return(true);
}
/// <summary>
/// Balances node.
/// </summary>
/// <returns>
/// The balance.
/// </returns>
public bool Balance()
{
if (this.Left != null)
{
this.Left.Balance();
}
if (this.Right != null)
{
this.Right.Balance();
}
this.UpdateHeight();
int leftHeight = 0;
int rightHeight = 0;
if (this.Left != null)
{
leftHeight = this.Left.Height;
}
if (this.Right != null)
{
rightHeight = this.Right.Height;
}
if (leftHeight - rightHeight > 1)
{
// right rotation
AVLTreeNode <T> z = this;
AVLTreeNode <T> y = this.Left;
AVLTreeNode <T> b = this.Left.Right;
bool zIsleftNode = z.Parent != null && ((AVLTreeNode <T>)z.Parent).Left == this;
z.Left = b;
if (b != null)
{
b.Parent = z;
}
y.Right = z;
if (y != null)
{
y.Parent = z.Parent;
if (y.Parent != null)
{
if (zIsleftNode)
{
((AVLTreeNode <T>)y.Parent).Left = y;
}
else
{
((AVLTreeNode <T>)y.Parent).Right = y;
}
}
}
z.Parent = y;
if (b != null)
{
b.UpdateHeight();
}
if (z != null)
{
z.UpdateHeight();
}
if (y != null)
{
y.UpdateHeight();
}
return(true);
}
if (rightHeight - leftHeight > 1)
{
// left rotation
AVLTreeNode <T> z = this;
AVLTreeNode <T> y = this.Right;
AVLTreeNode <T> b = this.Right.Left;
bool zIsleftNode = z.Parent != null && ((AVLTreeNode <T>)z.Parent).Left == this;
z.Right = b;
if (b != null)
{
b.Parent = z;
}
y.Left = z;
if (y != null)
{
y.Parent = z.Parent;
if (y.Parent != null)
{
if (zIsleftNode)
{
((AVLTreeNode <T>)y.Parent).Left = y;
}
else
{
((AVLTreeNode <T>)y.Parent).Right = y;
}
}
}
z.Parent = y;
if (b != null)
{
b.UpdateHeight();
}
if (z != null)
{
z.UpdateHeight();
}
if (y != null)
{
y.UpdateHeight();
}
return(true);
}
return(false);
}