public static IRedBlack <T> MakeRoot <T>(this IRedBlack <T> node)
{
if (node.IsRedNode())
{
return(new RedBlackNode <T>(true, node.Value, node.Left, node.Right));
}
return(node);
}
/// <summary>
/// Balances the given subtree.
/// </summary>
/// <typeparam name="T">Type of values stored in the tree.</typeparam>
/// <param name="isBlack">Is checked node black?</param>
/// <param name="value">Value stored in the node.</param>
/// <param name="left">New left node.</param>
/// <param name="right">New right node.</param>
/// <returns>Propagated node.</returns>
public static IRedBlack <T> Balance <T>(bool isBlack, T value, IRedBlack <T> left, IRedBlack <T> right)
{
if (isBlack && left.IsRedNode() && left.Left.IsRedNode())
{
var l = Black(left.Left.Value, left.Left.Left, left.Left.Right);
var r = Black(value, left.Right, right);
return(Red(left.Value, l, r));
}
if (isBlack && left.IsRedNode() && left.Right.IsRedNode())
{
var l = Black(left.Value, left.Left, left.Right.Left);
var r = Black(value, left.Right.Right, right);
return(Red(left.Right.Value, l, r));
}
if (isBlack && right.IsRedNode() && right.Left.IsRedNode())
{
var l = Black(value, left, right.Left.Left);
var r = Black(right.Value, right.Left.Right, right.Right);
return(Red(right.Left.Value, l, r));
}
if (isBlack && right.IsRedNode() && right.Right.IsRedNode())
{
var l = Black(value, left, right.Left);
var r = Black(right.Right.Value, right.Right.Left, right.Right.Right);
return(Red(right.Value, l, r));
}
// Tree is already balanced.
return(new RedBlackNode <T>(isBlack, value, left, right));
}
