/// <summary>
/// Adds a new node to the tree
/// </summary>
/// <param name="key">The node key</param>
/// <param name="value">The node data value</param>
/// <returns>Returns TRUE if a new node was added; returns FALSE if a node with the same key was found</returns>
public bool Add(TKey key, TValue value)
{
return(BinarySearchTreeNode <TKey, TValue> .Add(ref m_root, key, value, m_cmp));
}
/// <summary>
/// Removes a node from the tree
/// </summary>
/// <param name="key">The node key</param>
/// <returns>Returns TRUE if a node was removed; returns FALSE if a node with the same key was not found</returns>
public bool Remove(TKey key)
{
return(BinarySearchTreeNode <TKey, TValue> .Remove(ref m_root, key, m_cmp));
}
/// <summary>
/// Removes a node from the tree
/// </summary>
/// <param name="tree">The tree to remove a node</param>
/// <param name="key">The node key</param>
/// <param name="comparer">The key comparer</param>
/// <returns>Returns TRUE if a node was removed; returns FALSE if a node with the same key was not found</returns>
public static bool Remove(ref BinarySearchTreeNode <TKey, TValue> tree, TKey key, IComparer <TKey> comparer = null)
{
if (tree == null)
{
throw new ArgumentNullException(nameof(tree));
}
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
var cmp = comparer ?? Comparer <TKey> .Default;
var current = tree;
var parent = (BinarySearchTreeNode <TKey, TValue>)null;
int c;
// trace down the tree until we hit a NULL
while (current != null)
{
c = cmp.Compare(key, current.Value.Key);
if (c == 0)
{
break;
}
parent = current;
if (c < 0)
{
// current.Value.Key > key, search current's left subtree
current = current.Left;
}
else
{
// current.Value.Key < key, search current's right subtree
current = current.Right;
}
}
if (current == null)
{
// a node with the key was not found
return(false);
}
// if current has no right child, then current's left child becomes the node pointed to by the parent
if (current.Right == null)
{
if (parent == null)
{
tree = current.Left;
}
else
{
c = cmp.Compare(parent.Value.Key, current.Value.Key);
if (c > 0)
{
// parent.Value.Key > current.Value.Key, so make current's left child a left child of parent
parent.Left = current.Left;
}
else
{
// parent.Value.Key < current.Value.Key, so make current's left child a right child of parent
parent.Right = current.Left;
}
}
}
// if current's right child has no left child, then current's right child replaces current in the tree
else if (current.Right.Left == null)
{
current.Right.Left = current.Left;
if (parent == null)
{
tree = current.Right;
}
else
{
c = cmp.Compare(parent.Value.Key, current.Value.Key);
if (c > 0)
{
// parent.Value > current.Value, so make current's right child a left child of parent
parent.Left = current.Right;
}
else if (c < 0)
{
// parent.Value < current.Value, so make current's right child a right child of parent
parent.Right = current.Right;
}
}
}
// if current's right child has a left child, replace current with current's right child's left-most descendent
else
{
// We first need to find the right node's left-most child
var leftMost = current.Right.Left;
var leftMostParent = current.Right;
while (leftMost.Left != null)
{
leftMostParent = leftMost;
leftMost = leftMost.Left;
}
// the parent's left subtree becomes the leftMost's right subtree
leftMostParent.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 (parent == null)
{
tree = leftMost;
}
else
{
c = cmp.Compare(parent.Value.Key, current.Value.Key);
if (c > 0)
{
// parent.Value > current.Value, so make leftmost a left child of parent
parent.Left = leftMost;
}
else if (c < 0)
{
// parent.Value < current.Value, so make leftmost a right child of parent
parent.Right = leftMost;
}
}
}
// a node with the key was removed
return(true);
}
