public ITwoThree <T> Insert(T item, IComparer <T> comparer, out ITwoThree <T> splitLeft, out ITwoThree <T> splitRight, out T splitValue)
{
// Default split values.
splitLeft = splitRight = null;
splitValue = default(T);
// Get side to insert node.
var side = GetSide(item, comparer);
// Values are equal, no need to change tree.
if (IsSame(side))
{
return(this);
}
// Insert value into proper node.
T pv;
ITwoThree <T> pl, pr;
var child = GetChild(side);
var node = child.Insert(item, comparer, out pl, out pr, out pv);
// Insert propagated single node.
if (node != null)
{
return(node == child ? this : NewChangedNode(node, side));
}
// Insert propagated two nodes and value, meaning it split.
// Sinde this is 3-node, we are at full capacity and need to split too.
switch (side)
{
case Side.Left:
splitLeft = new TwoNode <T>(pv, pl, pr);
splitRight = new TwoNode <T>(Second, Middle, Right);
splitValue = First;
break;
case Side.Middle:
splitLeft = new TwoNode <T>(First, Left, pl);
splitRight = new TwoNode <T>(Second, pr, Right);
splitValue = pv;
break;
case Side.Right:
splitLeft = new TwoNode <T>(First, Left, Middle);
splitRight = new TwoNode <T>(pv, pl, pr);
splitValue = Second;
break;
}
return(null);
}
private ITwoThree <T> RedistributeOrMerge(T value, ITwoThree <T> left, ITwoThree <T> right, Side removedSide, out bool removed)
{
removed = false;
if (removedSide == Side.Right)
{
if (left is ThreeNode <T> )
{
// Right redistribute case.
var red = (ThreeNode <T>)left;
var l = new TwoNode <T>(red.First, red.Left, red.Middle);
var r = new TwoNode <T>(value, red.Right, right);
return(new TwoNode <T>(red.Second, l, r));
}
// Right merge case.
var m = (TwoNode <T>)left;
removed = true;
return(new ThreeNode <T>(m.Value, value, m.Left, m.Right, right));
}
if (removedSide == Side.Left)
{
if (right is ThreeNode <T> )
{
// Left redistribute case.
var led = (ThreeNode <T>)right;
var l = new TwoNode <T>(value, left, led.Left);
var r = new TwoNode <T>(led.Second, led.Middle, led.Right);
return(new TwoNode <T>(led.First, l, r));
}
// Left merge case.
var m = (TwoNode <T>)right;
removed = true;
return(new ThreeNode <T>(value, m.Value, left, m.Left, m.Right));
}
throw new InvalidOperationException();
}
private static ITwoThree <T> RedistributeRight(T first, T second, ITwoThree <T> left, ITwoThree <T> middle, ITwoThree <T> right)
{
// Case A
if (left is TwoNode <T> && middle is TwoNode <T> )
{
var sm = (TwoNode <T>)middle;
var l = left;
var r = new ThreeNode <T>(sm.Value, second, sm.Left, sm.Right, right);
return(new TwoNode <T>(first, l, r));
}
// Case B
if (middle is ThreeNode <T> )
{
var sm = (ThreeNode <T>)middle;
var l = left;
var m = new TwoNode <T>(sm.First, sm.Left, sm.Middle);
var r = new TwoNode <T>(second, sm.Right, right);
return(new ThreeNode <T>(first, sm.Second, l, m, r));
}
// Case C
if (left is ThreeNode <T> && middle is TwoNode <T> )
{
var sl = (ThreeNode <T>)left;
var sm = (TwoNode <T>)middle;
var l = new TwoNode <T>(sl.First, sl.Left, sl.Middle);
var m = new TwoNode <T>(first, sl.Right, sm.Left);
var r = new TwoNode <T>(second, sm.Right, right);
return(new ThreeNode <T>(sl.Second, sm.Value, l, m, r));
}
throw new InvalidOperationException();
}
private static ITwoThree <T> RedistributeMiddle(T first, T second, ITwoThree <T> left, ITwoThree <T> middle, ITwoThree <T> right)
{
// Case A
if (left is TwoNode <T> && right is TwoNode <T> )
{
var sl = (TwoNode <T>)left;
var l = new ThreeNode <T>(sl.Value, first, sl.Left, sl.Right, middle);
var r = right;
return(new TwoNode <T>(second, l, r));
}
// Case B
if (right is ThreeNode <T> )
{
var sr = (ThreeNode <T>)right;
var l = left;
var m = new TwoNode <T>(second, middle, sr.Left);
var r = new TwoNode <T>(sr.Second, sr.Middle, sr.Right);
return(new ThreeNode <T>(first, sr.First, l, m, r));
}
// Case C
if (left is ThreeNode <T> && right is TwoNode <T> )
{
var sl = (ThreeNode <T>)left;
var l = new TwoNode <T>(sl.First, sl.Left, sl.Middle);
var m = new TwoNode <T>(first, sl.Right, middle);
var r = right;
return(new ThreeNode <T>(sl.Second, second, l, m, r));
}
throw new InvalidOperationException();
}