// ###############################################
// Private / Protected stuff
// ###############################################
/// <summary>
/// Actual insert method
/// </summary>
/// <param name="pre">Predecessor| Node append new TreeNode on</param>
/// <param name="dir">Direction| Side on which the new Node should be put</param>
/// <param name="node"></param>
/// <returns></returns>
private bool Insert(BinSearchTreeNode pre, Direction dir, DoubleLinkBinSearchTreeNode node)
{
switch (dir)
{
case Direction.Unset:
if (Root != null)
{
return(false);
}
Root = node;
break;
case Direction.Left:
if (pre.Left != null)
{
return(false);
}
pre.Left = node;
((DoubleLinkBinSearchTreeNode)pre.Left).Previous = (DoubleLinkBinSearchTreeNode)pre;
break;
case Direction.Right:
if (pre.Right != null)
{
return(false);
}
pre.Right = node;
((DoubleLinkBinSearchTreeNode)pre.Right).Previous = (DoubleLinkBinSearchTreeNode)pre;
break;
default:
throw new ArgumentOutOfRangeException(nameof(dir), dir, null);
}
return(true);
}
/// <summary>
/// Actual delete method.
/// </summary>
/// <param name="pre"></param>
/// <param name="a"></param>
/// <param name="dir"></param>
/// <returns></returns>
internal override (bool, BinSearchTreeNode) Delete(BinSearchTreeNode pre, BinSearchTreeNode a, Direction dir)
{
if (a == null)
{
return(false, pre);
}
if (a.Type == BinSearchTreeNode.NodeType.Symmetric)
{
return(DelSymPred(a));
}
var b = a.Left ?? a.Right;
if (pre == null)
{
Root = b;
if (b != null)
{
((DoubleLinkBinSearchTreeNode)Root).Previous = null;
}
return(true, Root);
}
if (dir == Direction.Left)
{
pre.Left = b;
if (b != null)
{
((DoubleLinkBinSearchTreeNode)pre.Left).Previous = (DoubleLinkBinSearchTreeNode)pre;
}
}
else
{
pre.Right = b;
if (b != null)
{
((DoubleLinkBinSearchTreeNode)pre.Right).Previous = (DoubleLinkBinSearchTreeNode)pre;
}
}
return(true, pre);
}
/// <summary>
/// Helper method.
/// Use to "remove" node when node has two children
/// Basic idea is to copy
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
protected override (bool, BinSearchTreeNode) DelSymPred(BinSearchTreeNode node)
{
// get symmetric predecessor
var symPred = (DoubleLinkBinSearchTreeNode)(MaxNode(node.Left)).Item2;
// get node bevor symPred
var preSymPre = symPred.Previous;
symPred.Previous = null;
// Steal value from symPred
var tmp = symPred.Value;
// Check if the Node bevor symPred is node
if (preSymPre.Value == node.Value)
{
// remove symPred
node.Left = node.Left.Left;
if (node.Left != null)
{
((DoubleLinkBinSearchTreeNode)node.Left).Previous = (DoubleLinkBinSearchTreeNode)node;
}
}
else
{
// remove symPred
preSymPre.Right = symPred.Left;
if (preSymPre.Right != null)
{
((DoubleLinkBinSearchTreeNode)preSymPre.Right).Previous = (DoubleLinkBinSearchTreeNode)preSymPre.Right;
}
}
node.Value = tmp;
return(true, preSymPre);
}
