private BinaryTreeNode <T> FindNodeAndParent(T value, BinaryTreeNode <T> current, ref BinaryTreeNode <T> parent)
{
var comparison = value.CompareTo(current.Value);
while (comparison != 0)
{
if (comparison > 0) // value is bigger than current node search right subtree
{
parent = current;
current = current.RightChild;
}
else if (comparison < 0) // value is smaller than current node search left subtree
{
parent = current;
current = current.LeftChild;
}
if (current is null)
{
return(current);
}
else
{
comparison = value.CompareTo(current.Value);
}
}
return(current);
}
public BinarySearchTree(BinaryTreeNode <T> root) : base(root)
{
}
public void DeleteByValue(T value)
{
BinaryTreeNode <T> parent = null;
var toRemove = FindNodeAndParent(value, Root, ref parent);
var position = toRemove.CompareTo(parent);
// Case 1: if toRemove has no right child replace with leftChild
if (toRemove.RightChild is null)
{
if (position < 0)
{
parent.LeftChild = toRemove.LeftChild; // replace parent left child with left child of the node you want to remove;
}
else if (position > 0)
{
parent.RightChild = toRemove.LeftChild; // replace parent right child with left child of the node you want to remove;
}
else
{
throw new Exception("Current node is the same as its parent... You've got a bug! (or a single node tree)");
}
}
// Case 2: if toRemove right child has no left child replace with rightChild
else if (toRemove.RightChild.LeftChild is null)
{
if (position < 0)
{
parent.LeftChild = toRemove.RightChild; // replace parent right child with left child of the node you want to remove;
parent.LeftChild.LeftChild = toRemove.LeftChild ?? null;
}
else if (position > 0)
{
parent.RightChild = toRemove.RightChild; // replace parent right child with right child of the node you want to remove;
parent.RightChild.LeftChild = toRemove.LeftChild ?? null;
}
else
{
throw new Exception("Current node is the same as its parent... You've got a bug! (or a single node tree)");
}
}
// Case 3: if toRemove right child has left child replace with toRemove.rightChild's leftmost descendant
else if (toRemove.RightChild.LeftChild != null)
{
if (position < 0)
{
parent.LeftChild = FindLeftmostDescendant(toRemove.RightChild);
parent.LeftChild.LeftChild = toRemove.LeftChild ?? null;
parent.LeftChild.RightChild = toRemove.RightChild ?? null;
}
else if (position > 0)
{
var replacement = FindLeftmostDescendant(toRemove.RightChild);
FindParentNode(replacement).RemoveLeftChild();
parent.RightChild = replacement;
parent.RightChild.LeftChild = toRemove.LeftChild ?? null;
parent.RightChild.RightChild = toRemove.RightChild ?? null;
}
else
{
throw new Exception("Current node is the same as its parent... You've got a bug! (or a single node tree)");
}
}
_nodes.Remove(toRemove);
}