/// <summary>
/// Rotates the tree rooted at this node in a clockwise manner and recolours the root and pivot nodes accordingly.
/// </summary>
/// <returns>The new root of the tree</returns>
internal RedBlackNode <T> RotateRight()
{
RedBlackNode <T> pivot = this.Left;
this.Left = pivot.Right;
pivot.Right = this;
//fix heights
pivot.ResetHeight();
this.ResetHeight();
pivot.Right.SetColour(Colour.Red);
pivot.SetColour(Colour.Black);
return(pivot);
}
/// <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)
{
int compareResult = root.Value.CompareTo(value);
if (compareResult == 0)
{
// Node has two children, replace with in order predecessor and then recursively delete predecessor
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)
{
--this.Count;
root.Left.ResetHeight();
if (IsNodeRed(root.Left)) // node to delete is black but has red child that can be recoloured
{
root.Left.SetColour(Colour.Black);
done = true;
}
root = root.Left;
}
// Node only has Right child
else if (root.Right != null)
{
--this.Count;
root.Right.ResetHeight();
if (IsNodeRed(root.Right)) // node to delete is black but has red child that can be recoloured
{
root.Right.SetColour(Colour.Black);
done = true;
}
root = root.Right;
}
else // deleting leaf - done if red
{
--this.Count;
done = IsNodeRed(root);
root = null;
}
}
if (compareResult > 0)
{
if (root.Left != null)
{
root.Left = Delete(root.Left, value, ref done);
if (!done)
{
root = this.DeleteRebalanceLeft(root, ref done);
}
}
else
{
throw new ValueNotFoundException();
}
}
else if (compareResult < 0)
{
if (root.Right != null)
{
root.Right = Delete(root.Right, value, ref done);
if (!done)
{
root = this.DeleteRebalanceRight(root, ref done);
}
}
else
{
throw new ValueNotFoundException();
}
}
return(root);
}