public void AssertValidTree()
{
if (Root != null)
{
RedBlackNode <T> previousNode = null;
foreach (var node in InOrderNodeIterator)
{
if (previousNode != null && previousNode.Value.CompareTo(node.Value) >= 0)
{
throw new MeshNavException("Invalid Red Black Tree");
}
previousNode = node;
}
}
AssertValidTree(Root, out _);
}
/// <summary>
/// Moves a black root node down to it's two children and colours the root red
/// </summary>
/// <param name="root"></param>
private static void MoveBlackDown(RedBlackNode <T> root)
{
root.SetColor(Color.Red);
root.Left.SetColor(Color.Black);
root.Right.SetColor(Color.Black);
}
/// <summary>
/// Returns true if the node is red. Returns false if the node is black or null.
/// </summary>
private static bool IsNodeRed(RedBlackNode <T> node)
{
return(node != null && node.IsRed);
}
/// <summary>
/// Deletes the given value from the tree at the given root and ensures red-black tree properties are maintained ny
/// recolouring nodes and rotations
/// </summary>
/// <param name="root">The root node of the tree</param>
/// <param name="value">The value to delete</param>
/// <param name="done">A flag determining if more rebalancing and recolouring is necessary</param>
/// <returns>The new root of the tree as it may have changed</returns>
private RedBlackNode <T> Delete(RedBlackNode <T> root, T value, ref bool done)
{
var compareResult = root.Value.CompareTo(value);
if (compareResult == 0)
{
if (root.Left != null && root.Right != null)
{
compareResult = 1;
root.Value = root.InOrderPredecessor.Value;
value = root.Value;
root.ResetHeight();
}
// Node only has left child
else if (root.Left != null)
{
--Count;
root.Left.ResetHeight();
if (IsNodeRed(root.Left)) // node to delete is black but has red child that can be recoloured
{
root.Left.SetColor(Color.Black);
done = true;
}
root = root.Left;
}
// Node only has Right child
else if (root.Right != null)
{
--Count;
root.Right.ResetHeight();
if (IsNodeRed(root.Right)) // node to delete is black but has red child that can be recoloured
{
root.Right.SetColor(Color.Black);
done = true;
}
root = root.Right;
}
else // deleting leaf - done if red
{
--Count;
done = IsNodeRed(root);
root = null;
}
}
// ReSharper disable PossibleNullReferenceException
if (compareResult > 0)
{
if (root.Left != null)
{
root.Left = Delete(root.Left, value, ref done);
if (!done)
{
root = DeleteRebalanceLeft(root, ref done);
}
}
else
{
throw new MeshNavException("Value not found");
}
}
else if (compareResult < 0)
{
if (root.Right != null)
{
root.Right = Delete(root.Right, value, ref done);
if (!done)
{
root = DeleteRebalanceRight(root, ref done);
}
}
else
{
throw new MeshNavException("Value not found");
}
}
// ReSharper restore PossibleNullReferenceException
return(root);
}