private void LeftRotation()
{
// a
// \
// b
// \
// c
//
// becomes
// b
// / \
// a c
AVLTreeNode <TNode> newRoot = Right;
// replace the current root with the new root
ReplaceRoot(newRoot);
// take ownership of right's left child as right (now parent)
Right = newRoot.Left;
// the new root takes this as it's left
newRoot.Left = this;
}
/// <summary>
/// Removes the specified value from the tree if found
/// </summary>
/// <param name="value">The node value to find</param>
/// <returns>True if found and removed, otherwise, false</returns>
public bool Remove(T value)
{
AVLTreeNode <T> current = Find(value);
if (current == null)
{
// Not found
return(false);
}
// Grab the parent of the node to be removed
AVLTreeNode <T> treeToBalance = current.Parent;
// Decrement the count
Count--;
// If Current has no right child, current's left node replaces current
if (current.Right == null)
{
if (current.Parent == null)
{
Head = current.Left;
if (Head != null)
{
Head.Parent = null;
}
}
else
{
int result = current.Parent.CompareTo(current.Value);
if (result > 0)
{
// If parent value is greater than current value,
// make the current left child a left child of parent
current.Parent.Left = current.Left;
}
else if (result < 0)
{
// If parent value is less than the current value,
// make the current left child a right child of parent
current.Parent.Right = current.Left;
}
}
}
else if (current.Right.Left == null)
{
// Current's right child has no left child, current's right child replaces current
current.Right.Left = current.Left;
if (current.Parent == null)
{
Head = current.Right;
if (Head != null)
{
Head.Parent = null;
}
}
else
{
int result = current.Parent.CompareTo(current.Value);
if (result > 0)
{
// If parent value is greater than the current value,
// make the current right child a left child of parent
current.Parent.Left = current.Right;
}
else if (result < 0)
{
// If parent value is less than the current value
// make the current right child a right child of parent
current.Parent.Right = current.Right;
}
}
}
else
{
// Current's right child has a left child
// Replace current with current's right child's leftmost child
// Get the right's leftmost child
AVLTreeNode <T> leftmost = current.Right.Left;
while (leftmost.Left != null)
{
leftmost = leftmost.Left;
}
// The parent's left subtree becomes the leftmost's right subtree
leftmost.Parent.Left = leftmost.Right;
// Assign leftmost's child nodes
leftmost.Left = current.Left;
leftmost.Right = current.Right;
if (current.Parent == null)
{
Head = leftmost;
if (Head != null)
{
Head.Parent = null;
}
}
else
{
int result = current.Parent.CompareTo(current.Value);
if (result > 0)
{
// If parent value is greater than current value
// make leftmost the parent's left child
current.Parent.Left = leftmost;
}
else if (result < 0)
{
// If parent value is less than current value
// make leftmost the the parent's right child
current.Parent.Right = leftmost;
}
}
}
// Rebalance
if (treeToBalance != null)
{
treeToBalance.Balance();
}
else
{
if (Head != null)
{
Head.Balance();
}
}
return(true);
}
public void Clear()
{
Head = null;
Count = 0;
}
/// <summary>
/// AVLTreeNode constructor
/// </summary>
/// <param name="value">The value of the node</param>
/// <param name="parent">The parent node of the node</param>
/// <param name="tree">The tree the node is contained in</param>
public AVLTreeNode(TNode value, AVLTreeNode <TNode> parent, AVLTree <TNode> tree)
{
Value = value;
Parent = parent;
_tree = tree;
}
/// <summary>
/// Removes the first occurance of the specified value from the tree.
/// </summary>
/// <param name="value">The value to remove</param>
/// <returns>True if the value was removed, false otherwise</returns>
public bool Remove(T value)
{
AVLTreeNode <T> current;
current = Find(value);
if (current == null)
{
return(false);
}
AVLTreeNode <T> treeToBalance = current.Parent;
Count--;
// Case 1: If current has no right child, then current's left replaces current
if (current.Right == null)
{
if (current.Parent == null)
{
Head = current.Left;
if (Head != null)
{
Head.Parent = null;
}
}
else
{
int result = current.Parent.CompareTo(current.Value);
if (result > 0)
{
// if parent value is greater than current value
// make the current left child a left child of parent
current.Parent.Left = current.Left;
}
else if (result < 0)
{
// if parent value is less than current value
// make the current left child a right child of parent
current.Parent.Right = current.Left;
}
}
}
// Case 2: If current's right child has no left child, then current's right child
// replaces current
else if (current.Right.Left == null)
{
current.Right.Left = current.Left;
if (current.Parent == null)
{
Head = current.Right;
if (Head != null)
{
Head.Parent = null;
}
}
else
{
int result = current.Parent.CompareTo(current.Value);
if (result > 0)
{
// if parent value is greater than current value
// make the current right child a left child of parent
current.Parent.Left = current.Right;
}
else if (result < 0)
{
// if parent value is less than current value
// make the current right child a right child of parent
current.Parent.Right = current.Right;
}
}
}
// Case 3: If current's right child has a left child, replace current with current's
// right child's left-most child
else
{
// find the right's left-most child
AVLTreeNode <T> leftmost = current.Right.Left;
while (leftmost.Left != null)
{
leftmost = leftmost.Left;
}
// the parent's left subtree becomes the leftmost's right subtree
leftmost.Parent.Left = leftmost.Right;
// assign leftmost's left and right to current's left and right children
leftmost.Left = current.Left;
leftmost.Right = current.Right;
if (current.Parent == null)
{
Head = leftmost;
if (Head != null)
{
Head.Parent = null;
}
}
else
{
int result = current.Parent.CompareTo(current.Value);
if (result > 0)
{
// if parent value is greater than current value
// make leftmost the parent's left child
current.Parent.Left = leftmost;
}
else if (result < 0)
{
// if parent value is less than current value
// make leftmost the parent's right child
current.Parent.Right = leftmost;
}
}
}
if (treeToBalance != null)
{
treeToBalance.Balance();
}
else
{
if (Head != null)
{
Head.Balance();
}
}
return(true);
}
