private RedBlackNode <T> DeleteRebalanceLeft(RedBlackNode <T> root, ref bool done)
{
// Rotation to reduce the red sibling case to the easier to handle black sibling case
RedBlackNode <T> parent = root;
RedBlackNode <T> sibling = root.Right;
if (IsNodeRed(sibling))
{
root = root.RotateLeft();
sibling = parent.Right;
}
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.Right))
{
parent = parent.RotateLeft();
}
else
{
parent.Right = parent.Right.RotateRight();
parent = parent.RotateLeft();
}
parent.SetIsRed(parentIsRed);
parent.Left.SetColour(Colour.Black);
parent.Right.SetColour(Colour.Black);
if (sameRoot)
{
root = parent;
}
else
{
root.Left = parent;
}
done = true;
}
}
return(root);
}
/// <summary>
/// Deals with the case where after inserting a node to the right we have a red node as a right sub-child of its parent and has another red node as a left subchild.
/// </summary>
private RedBlackNode <T> Insert_Case3_RightLeftReds(RedBlackNode <T> root)
{
root.Right = root.Right.RotateRight();
root = root.RotateLeft();
return(root);
}
/// <summary>
/// Deals with the case where after an insert to the right we have two red nodes as right sub-children of each-other
/// </summary>
private RedBlackNode <T> Insert_Case2_TwoRightReds(RedBlackNode <T> root)
{
if (IsNodeRed(root.Right.Right))
{
root = root.RotateLeft();
}
else if (IsNodeRed(root.Right.Left))
{
root = Insert_Case3_RightLeftReds(root);
}
return(root);
}