/// <summary>
/// Add a single node to the tree.
/// </summary>
/// <param name="key">Key value to add.</param>
public void Add(TKey key)
{
if (root is null)
{
root = new AvlTreeNode <TKey>(key);
}
else
{
root = Add(root, key);
}
Count++;
}
/// <summary>
/// Remove a node from the tree.
/// </summary>
/// <param name="key">Key value to remove.</param>
public void Remove(TKey key)
{
if (root is null)
{
throw new InvalidOperationException("Tree is empty!");
}
else if (!Contains(key))
{
throw new KeyNotFoundException($"Key {key} is not in the tree");
}
else
{
root = Remove(root, key);
Count--;
}
}
/// <summary>
/// Recursive function to remove node from tree.
/// </summary>
/// <param name="node">Node to check for key.</param>
/// <param name="key">Key value to remove.</param>
/// <returns>New node with key removed.</returns>
private AvlTreeNode <TKey>?Remove(AvlTreeNode <TKey> node, TKey key)
{
// Normal binary search tree removal
var compareResult = comparer.Compare(key, node.Key);
if (compareResult < 0)
{
node.Left = Remove(node.Left !, key);
}
else if (compareResult > 0)
{
node.Right = Remove(node.Right !, key);
}
else
{
if (node.Left is null && node.Right is null)
{
return(null);
}
/// <summary>
/// Recursively function to add a node to the tree.
/// </summary>
/// <param name="node">Node to check for null leaf.</param>
/// <param name="key">Key value to add.</param>
/// <returns>New node with key inserted.</returns>
private AvlTreeNode <TKey> Add(AvlTreeNode <TKey> node, TKey key)
{
// Regular binary search tree insertion
int compareResult = comparer.Compare(key, node.Key);
if (compareResult < 0)
{
if (node.Left is null)
{
var newNode = new AvlTreeNode <TKey>(key);
node.Left = newNode;
}
else
{
node.Left = Add(node.Left, key);
}
}
else if (compareResult > 0)
{
if (node.Right is null)
{
var newNode = new AvlTreeNode <TKey>(key);
node.Right = newNode;
}
else
{
node.Right = Add(node.Right, key);
}
}
else
{
throw new ArgumentException($"Key \"{key}\" already exists in tree!");
}
// Check all of the new node's ancestors for inbalance and perform
// necessary rotations
node.UpdateBalanceFactor();
return(Rebalance(node));
}