/// <summary>
/// PostOrder traversal the tree, left -> right -> root
/// </summary>
/// <param name="currentNode"></param>
/// <returns></returns>
public IEnumerable <Node <T, U> > PostOrder(Node <T, U> currentNode)
{
if (currentNode != null)
{
//recursively call left child
if (currentNode.HasLeftChild())
{
foreach (var node in PostOrder(currentNode.LeftChild))
{
yield return(node);
}
}
//recursively call right child
if (currentNode.HasRightChild())
{
foreach (var node in PostOrder(currentNode.RightChild))
{
yield return(node);
}
}
//parent
yield return(currentNode);
}
}
private void _Remove(Node <T, U> currentNode)
{
//is leaf
if (currentNode.IsLeaf())
{
//is left child
if (currentNode.IsLeftChild())
{
currentNode.Parent.LeftChild = null;
}
//is right child
else
{
currentNode.Parent.RightChild = null;
}
}
//is not leaf
else
{
//is left child
if (currentNode.IsLeftChild())
{
//has only left child
if (currentNode.HasLeftChild() && !currentNode.HasRightChild())
{
currentNode.Parent.LeftChild = currentNode.LeftChild;
currentNode.LeftChild.Parent = currentNode.Parent;
}
//has only right child
if (!currentNode.HasLeftChild() && currentNode.HasRightChild())
{
currentNode.Parent.LeftChild = currentNode.RightChild;
currentNode.RightChild.Parent = currentNode.Parent;
}
//has both children
else
{
}
}
//is right child
else
{
}
}
}
private void _Put(T key, U value, Node <T, U> currentNode, bool changeable = false)
{
//if key less than currentNode, _put to left
if (key.CompareTo(currentNode.Key) < 0)
{
if (currentNode.HasLeftChild())
{
_Put(key, value, currentNode.LeftChild);
}
else
{
currentNode.LeftChild = new Node <T, U>(key, value, parent: currentNode);
}
}
else if (key.CompareTo(currentNode.Key) > 0) //_put to right
{
if (currentNode.HasRightChild())
{
_Put(key, value, currentNode.RightChild);
}
else
{
currentNode.RightChild = new Node <T, U>(key, value, parent: currentNode);
}
}
else //equals to current key
{
if (!changeable)
{
throw new Exception("The Id already exists!");
}
else
{
currentNode.Payload = value;
}
}
}