public void Clear()
{
_head = null;
_count = 0;
RemoveNode?.Invoke("Work Clear Method");
}
public bool Remove(T value)
{
BinaryTreeNode <T> current;
BinaryTreeNode <T> parent;
// Search the NODE for removal.
current = FindWithParent(value, out parent);
if (current == null)
{
return(false);
}
_count--;
// The first option: the deleted node does not have a right descendant.
if (current.Right == null)
{
// Remove the root
if (parent == null)
{
_head = current.Left;
RemoveNode?.Invoke("The head changed");
}
else
{
int result = parent.CompareTo(current.Value);
if (result > 0)
{
//If the value of the parent node is greater
//than the value of the node being deleted,
//make the left descendant of the current node
// to the left descendant of the parent node.
parent.Left = current.Left;
RemoveNode?.Invoke("make the left descendant of the current node to the left descendant of the parent node");
}
else if (result < 0)
{
// If the value of the parent node is less than the value
//of the node being deleted, make the left descendant
//of the current node the right descendant of the
//parent node.
parent.Right = current.Left;
RemoveNode?.Invoke("make the left descendant of the current node to the right descendant of the parent node");
}
}
}
// The second option: the deleted node has a right descendant, which has no left descendant.
else if (current.Right.Left == null)
{
current.Right.Left = current.Left;
// Remove the root
if (parent == null)
{
_head = current.Right;
RemoveNode?.Invoke("The head changed");
}
else
{
int result = parent.CompareTo(current.Value);
if (result > 0)
{
// If the value of the parent node is greater than the value of the node being deleted -
// make the right descendant of the current node the left descendant of the parent node.
parent.Left = current.Right;
RemoveNode?.Invoke("make the right descendant of the current node the left descendant of the parent node");
}
else if (result < 0)
{
// If the value of the parent node is less than the value of the node being deleted -
// make the right descendant of the current node the right descendant of the parent node.
parent.Right = current.Right;
RemoveNode?.Invoke("make the right descendant of the current node the right descendant of the parent node");
}
}
}
// The third option: the deleted node has a right descendant that has a left descendant.
else
{
BinaryTreeNode <T> leftmostParent = current.Right;
BinaryTreeNode <T> leftmost = current.Right.Left;
// search for the leftmost descendant
while (leftmost.Left != null)
{
leftmostParent = leftmost;
leftmost = leftmost.Left;
}
// The right subtree of the leftmost node becomes the left subtree of its parent node.
leftmostParent.Left = leftmost.Right;
RemoveNode?.Invoke("The right subtree of the leftmost node becomes the left subtree of its parent node");
// Assign the leftmost node as the left descendant - the left descendant of the deleted node,
// and as the right descendant is the right descendant of the node to be deleted.
leftmost.Left = current.Left;
leftmost.Right = current.Right;
RemoveNode?.Invoke("Assign the leftmost node as the left descendant - the left descendant of the deleted node," +
"and as the right descendant is the right descendant of the node to be deleted. ");
if (parent == null)
{
_head = leftmost;
RemoveNode?.Invoke("The head changed");
}
else
{
int result = parent.CompareTo(current.Value);
if (result > 0)
{
// If the value of the parent node (parent) is greater than the value of the node being deleted (current) -
// make the leftmost descendant of the deleted node (leftmost) - the left descendant of its parent (parent).
parent.Left = leftmost;
RemoveNode?.Invoke("make the leftmost descendant of the deleted node (leftmost) - the left descendant of its parent (parent).");
}
else if (result < 0)
{
// If the value of the parent node (parent) is less than the value of the node being deleted (current) -
// make the leftmost descendant of the deleted node (leftmost) - the right descendant of its parent (parent).
parent.Right = leftmost;
RemoveNode?.Invoke("make the leftmost descendant of the deleted node(leftmost) -the right descendant of its parent(parent).");
}
}
}
return(true);
}
