/// <summary>
/// Rebalances the root after a black node was deleted in the right sub-tree
/// </summary>
/// <param name="root"></param>
/// <param name="done"></param>
/// <returns></returns>
private RedBlackNode <T> DeleteRebalanceRight(RedBlackNode <T> root, ref bool done)
{
RedBlackNode <T> parent = root;
RedBlackNode <T> sibling = root.Left;
// Rotation to reduce the red sibling case to the easier to handle black sibling case
if (IsNodeRed(sibling))
{
root = root.RotateRight();
sibling = parent.Left;
}
if (sibling != null)
{
if (!IsNodeRed(sibling.Left) && !IsNodeRed(sibling.Right))
{
if (IsNodeRed(parent))
{
done = true;
}
parent.SetColour(Colour.Black);
sibling.SetColour(Colour.Red);
}
else
{
bool parentIsRed = parent.IsRed;
bool sameRoot = root == parent;
if (IsNodeRed(sibling.Left))
{
parent = parent.RotateRight();
}
else
{
parent.Left = parent.Left.RotateLeft();
parent = parent.RotateRight();
}
parent.SetIsRed(parentIsRed);
parent.Left.SetColour(Colour.Black);
parent.Right.SetColour(Colour.Black);
if (sameRoot)
{
root = parent;
}
else
{
root.Right = parent;
}
done = true;
}
}
return(root);
}
/// <summary>
/// Deals with the case where after inserting a node to the left we have a red node as a left sub-child of its parent and has another red node as a right subchild.
/// </summary>
private RedBlackNode <T> Insert_Case3_LeftRightReds(RedBlackNode <T> root)
{
root.Left = root.Left.RotateLeft();
root = root.RotateRight();
return(root);
}
/// <summary>
/// Deals with the case where after an insert to the left we have two red nodes as left sub-children of each-other
/// </summary>
private RedBlackNode <T> Insert_Case2_TwoLeftReds(RedBlackNode <T> root)
{
if (IsNodeRed(root.Left.Left))
{
root = root.RotateRight();
}
else if (IsNodeRed(root.Left.Right))
{
root = Insert_Case3_LeftRightReds(root);
}
return(root);
}