public override void Split(TreeNode twoFourNode, int element)
{
TwoFourTreeNode p;
twoFourNode = (TwoFourTreeNode) twoFourNode;
if (twoFourNode.parent == null)
{
p = new TwoFourTreeNode();
}
else
{
p = (TwoFourTreeNode) twoFourNode.parent;
}
TwoFourTreeNode n1 = new TwoFourTreeNode();
TwoFourTreeNode n2 = new TwoFourTreeNode();
int[] elements = { element, twoFourNode.elements[0], twoFourNode.elements[1], twoFourNode.elements[2] };
int middle;
this.SortElements(elements, elements.Length);
n1.elements[0] = elements[0];
n1.elements[1] = elements[1];
n2.elements[0] = elements[3];
middle = elements[2];
n1.parent = p;
n2.parent = p;
if (p.NumberOfElements() == 0)
{
p.children[0] = n1;
p.children[1] = n2;
this.root = p;
}
else if (p.NumberOfElements() == 1)
{
if (n2.elements[0] < p.elements[0])
{
p.children[2] = p.children[1];
p.children[0] = n1;
p.children[1] = n2;
}
else
{
p.children[1] = n1;
p.children[2] = n2;
}
}
else if (p.NumberOfElements() == 2)
{
if (n2.elements[0] < p.elements[0] && n2.elements[0] < p.elements[1])
{
p.children[3] = p.children[2];
p.children[2] = p.children[1];
p.children[0] = n1;
p.children[1] = n2;
}
else if (n1.elements[1] > p.elements[0] && n1.elements[1] > p.elements[1])
{
p.children[2] = n1;
p.children[3] = n2;
}
else
{
p.children[3] = p.children[2];
p.children[1] = n1;
p.children[2] = n2;
}
}
else if (p.NumberOfElements() == 3)
{
if (n2.elements[0] < p.elements[0])
{
p.children[4] = p.children[3];
p.children[3] = p.children[2];
p.children[2] = p.children[1];
p.children[1] = n2;
p.children[0] = n1;
}
else if (n1.elements[0] > p.elements[0] && n2.elements[0] < p.elements[1])
{
p.children[4] = p.children[3];
p.children[3] = p.children[2];
p.children[2] = n2;
p.children[1] = n1;
}
else if (n1.elements[0] > p.elements[1] && n2.elements[0] < p.elements[2])
{
p.children[4] = p.children[3];
p.children[3] = n2;
p.children[2] = n1;
}
else
{
p.children[3] = n1;
p.children[4] = n2;
}
}
//if it is not a leaf check
if (twoFourNode.IsLeaf() == false)
{
twoFourNode.children[0].parent = n1;
twoFourNode.children[1].parent = n1;
twoFourNode.children[2].parent = n1;
twoFourNode.children[3].parent = n2;
twoFourNode.children[4].parent = n2;
n1.children[0] = twoFourNode.children[0];
n1.children[1] = twoFourNode.children[1];
n1.children[2] = twoFourNode.children[2];
n2.children[0] = twoFourNode.children[3];
n2.children[1] = twoFourNode.children[4];
}
if (p.NumberOfElements() == 3)
{
this.Split(p, middle);
}
else if (p.NumberOfElements() < this.limit)
{
p.elements[p.NumberOfElements()] = middle;
this.SortElements(p.elements, p.NumberOfElements());
}
}
void TakeElementFromThreeNextRightSibling(TwoFourTreeNode p, TwoFourTreeNode node)
{
node.elements[0] = p.elements[0];
p.elements[0] = p.children[1].elements[0];
p.children[1].elements[0] = p.elements[1];
p.elements[1] = p.children[2].elements[0];
p.children[2].elements[0] = p.elements[2];
p.elements[2] = p.children[3].elements[0];
if (p.children[3].NumberOfElements() == 2)
{
p.children[3].elements[0] = p.children[3].elements[1];
p.children[3].elements[1] = 0;
}
else if (p.children[3].NumberOfElements() == 3)
{
p.children[3].elements[0] = p.children[3].elements[1];
p.children[3].elements[1] = p.children[3].elements[2];
p.children[3].elements[2] = 0;
}
if (node.IsLeaf() == false)
{
node.children[1] = p.children[1].children[0];
p.children[1].children[0] = p.children[1].children[1];
p.children[1].children[1] = p.children[2].children[0];
p.children[2].children[0] = p.children[2].children[1];
p.children[2].children[1] = p.children[3].children[0];
if (p.children[3].NumberOfElements() == 1)
{
p.children[3].children[0] = p.children[3].children[1];
p.children[3].children[1] = p.children[3].children[2];
p.children[3].children[2] = null;
}
else if (p.children[3].NumberOfElements() == 2)
{
p.children[3].children[0] = p.children[3].children[1];
p.children[3].children[1] = p.children[3].children[2];
p.children[3].children[2] = p.children[3].children[3];
p.children[3].children[3] = null;
}
node.children[1].parent = node;
p.children[1].children[1].parent = p.children[1];
p.children[2].children[1].parent = p.children[2];
}
}
//completes the deletion when node n is empty by either, removing the root, redistributing values, or merging nodes.
//Note : if n is internal, it has only one child
public void Fix(TwoFourTreeNode node)
{
TwoFourTreeNode p;
if (node.parent == null) //No parent means it is root node
{
if (node.children[0] == null) { return; }
//remove root and set the children as a root
this.root = node.children[0];
this.root.parent = null;
}
else
{
p = (TwoFourTreeNode)node.parent;
//situation represents both the possibility of merge and the sibling with two elements
//if it returns -1, means there is no siblings with two elements
//if it is bigger than -1, means that index has the two elements
int situation = this.HasChildWithTwoElement(p);
//check for redistrubution is possible or not
if (situation > -1)
{
//redistrubute
this.Redistrubute(node, p, situation);
}
//redistrubuting not possible, thus merge
//for merging we have 5 different situation; 2 for parent with one element, 3 for parent with two element
else
{
this.Merge(node);
}
if (node.parent.NumberOfElements() == 0)
{
this.Fix(p);
}
}
}
void Redistrubute(TwoFourTreeNode node, TwoFourTreeNode p, int situation)
{
//there is two different situation if the parent has two nodes
if (p.NumberOfElements() == 1)
{
if (situation == 20 || situation == 30)
{
this.TakeElementFromNextLeftSibling(p, node, 0);
}
else
{
this.TakeElementFromNextRightSibling(p, node, 0);
}
}
//there is six different situation if the parent has three nodes
else if (p.NumberOfElements() == 2)
{
//Check for which children is empty
if (p.children[0].NumberOfElements() == 0)
{
//situation can be 1 or 2
if (situation == 21 || situation == 31)
{
this.TakeElementFromNextRightSibling(p, node, 0);
}
else
{
this.TakeElementFromTwoNextRightSibling(p, node, 0);
}
}
else if (p.children[1].NumberOfElements() == 0)
{
//situation can be 0 or 2
if (situation == 20 || situation == 30)
{
this.TakeElementFromNextLeftSibling(p, node, 0);
}
else
{
this.TakeElementFromNextRightSibling(p, node, 1);
}
}
else if (p.children[2].NumberOfElements() == 0)
{
//situation can be 0 or 1
if (situation == 20 || situation == 30)
{
this.TakeElementFromTwoNextLeftSibling(p, node, 2);
}
else
{
this.TakeElementFromNextLeftSibling(p, node, 1);
}
}
}
else if (p.NumberOfElements() == 3)
{
//Check for which children is empty
if (p.children[0].NumberOfElements() == 0)
{
//situation can be 1 2 or 3
switch (situation)
{
case 21:
this.TakeElementFromNextRightSibling(p, node, 0);
break;
case 31:
this.TakeElementFromNextRightSibling(p, node, 0);
break;
case 22:
this.TakeElementFromTwoNextRightSibling(p, node, 0);
break;
case 32:
this.TakeElementFromTwoNextRightSibling(p, node, 0);
break;
case 23:
this.TakeElementFromThreeNextRightSibling(p, node);
break;
case 33:
this.TakeElementFromThreeNextRightSibling(p, node);
break;
}
}
else if (p.children[1].NumberOfElements() == 0)
{
//situation can be 0 2 or 3
switch (situation)
{
case 20:
this.TakeElementFromNextLeftSibling(p, node, 0);
break;
case 30:
this.TakeElementFromNextLeftSibling(p, node, 0);
break;
case 22:
this.TakeElementFromNextRightSibling(p, node, 1);
break;
case 32:
this.TakeElementFromNextRightSibling(p, node, 1);
break;
case 23:
this.TakeElementFromTwoNextRightSibling(p, node, 1);
break;
case 33:
this.TakeElementFromTwoNextRightSibling(p, node, 1);
break;
}
}
else if (p.children[2].NumberOfElements() == 0)
{
//situation can be 0 1 or 3
switch (situation)
{
case 20:
this.TakeElementFromTwoNextLeftSibling(p, node, 2);
break;
case 30:
this.TakeElementFromTwoNextLeftSibling(p, node, 2);
break;
case 21:
this.TakeElementFromNextLeftSibling(p, node, 1);
break;
case 31:
this.TakeElementFromNextLeftSibling(p, node, 1);
break;
case 23:
this.TakeElementFromNextRightSibling(p, node, 2);
break;
case 33:
this.TakeElementFromNextRightSibling(p, node, 2);
break;
}
}
else
{
//situation can be 0 1 or 2
switch (situation)
{
case 20:
this.TakeElementFromThreeNextLeftSibling(p, node);
break;
case 30:
this.TakeElementFromThreeNextLeftSibling(p, node);
break;
case 21:
this.TakeElementFromTwoNextLeftSibling(p, node, 3);
break;
case 31:
this.TakeElementFromTwoNextLeftSibling(p, node, 3);
break;
case 22:
this.TakeElementFromNextLeftSibling(p, node, 2);
break;
case 32:
this.TakeElementFromNextLeftSibling(p, node, 2);
break;
}
}
}
}
