void Redistrubute(TwoThreeTreeNode node, TwoThreeTreeNode p, int situation)
{
//there is two different situation if the parent has two nodes
if (p.NumberOfElements() == 1)
{
if (situation == 20)
{
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)
{
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)
{
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)
{
this.TakeElementFromTwoNextLeftSibling(p, node, 2);
}
else
{
this.TakeElementFromNextLeftSibling(p, node, 1);
}
}
}
}
public void Delete(int element)
{
TwoThreeTreeNode shouldFixed = (TwoThreeTreeNode)this.DeleteElement(element);
if (shouldFixed != null)
{
Fix(shouldFixed);
}
}
public void Fix(TwoThreeTreeNode node)
{
TwoThreeTreeNode p;
if (node.parent == null)
{
if (node.children[0] == null)
{
return;
}
root = node.children[0];
root.parent = null;
}
else
{
p = (TwoThreeTreeNode)node.parent;
int situation = HasChildWithTwoElement(p);
if (situation > -1)
{
Redistrubute(node, p, situation);
}
else
{
Merge(node);
}
if (node.parent.NumberOfElements() == 0)
{
Fix((TwoThreeTreeNode)node.parent);
}
}
}
void Redistrubute(TwoThreeTreeNode node, TwoThreeTreeNode p, int situation)
{
//there is two different situation if the parent has two nodes
if (p.NumberOfElements() == 1)
{
if (situation == 20)
{
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)
{
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)
{
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)
{
this.TakeElementFromTwoNextLeftSibling(p, node, 2);
}
else
{
this.TakeElementFromNextLeftSibling(p, node, 1);
}
}
}
}
//Recursively split to balance the tree
public override void Split(TreeNode twoThreeNode, int element)
{
TwoThreeTreeNode p;
if (twoThreeNode.parent == null)
{
p = new TwoThreeTreeNode();
}
else
{
p = (TwoThreeTreeNode) twoThreeNode.parent;
}
TwoThreeTreeNode n1 = new TwoThreeTreeNode();
TwoThreeTreeNode n2 = new TwoThreeTreeNode();
//finding the smallest, middle and large elements
int small, middle, large;
if (element < twoThreeNode.elements[0])
{
small = element;
middle = twoThreeNode.elements[0];
large = twoThreeNode.elements[1];
}
else if (element > twoThreeNode.elements[1])
{
small = twoThreeNode.elements[0];
middle = twoThreeNode.elements[1];
large = element;
}
else
{
small = twoThreeNode.elements[0];
middle = element;
large = twoThreeNode.elements[1];
}
//set smallest and largest keys to the n1 and n2 respectively
n1.elements[0] = small;
n2.elements[0] = large;
//Make p the parent node of n1 and n2
n1.parent = p;
n2.parent = p;
if (p.NumberOfElements() == 0)
{
p.children[0] = n1;
p.children[1] = n2;
this.root = p;
n1.isLeaf = true;
n2.isLeaf = true;
}
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;
}
n1.isLeaf = true;
n2.isLeaf = true;
}
else
{
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[0] > p.elements[0] && n1.elements[0] > 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;
}
}
//if it is not a leaf check
if (twoThreeNode.IsLeaf() == false)
{
twoThreeNode.children[0].parent = n1;
twoThreeNode.children[1].parent = n1;
twoThreeNode.children[2].parent = n2;
twoThreeNode.children[3].parent = n2;
n1.children[0] = twoThreeNode.children[0];
n1.children[1] = twoThreeNode.children[1];
n2.children[0] = twoThreeNode.children[2];
n2.children[1] = twoThreeNode.children[3];
n1.isLeaf = false;
n2.isLeaf = false;
}
if (p.NumberOfElements() == 2)
{
this.Split(p, middle);
if (n1.children[0] != null || n2.children[0] != null)
{
if (n1.children[0].IsLeaf() || n2.children[0].IsLeaf())
{
n1.isLeaf = false;
n2.isLeaf = false;
}
}
else
{
n1.isLeaf = true;
n2.isLeaf = true;
}
n1.parent.isLeaf = false;
n2.parent.isLeaf = false;
}
else if (p.NumberOfElements() == 1)
{
if (p.elements[0] < middle)
{
p.elements[1] = middle;
}
else
{
p.elements[1] = p.elements[0];
p.elements[0] = middle;
}
}
else
{
p.elements[0] = middle;
}
}
//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(TwoThreeTreeNode node)
{
TwoThreeTreeNode 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;
//this.root.children[2] = node.children[2];
}
else
{
p = (TwoThreeTreeNode) 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( (TwoThreeTreeNode) node.parent);
}
}
}
public override void Split(TreeNode twoThreeNode, int element)
{
TwoThreeTreeNode p;
if (twoThreeNode.parent == null)
{
p = new TwoThreeTreeNode();
}
else
{
p = (TwoThreeTreeNode)twoThreeNode.parent;
}
TwoThreeTreeNode n1 = new TwoThreeTreeNode();
TwoThreeTreeNode n2 = new TwoThreeTreeNode();
int small, middle, large;
if (element < twoThreeNode.elements[0])
{
small = element;
middle = twoThreeNode.elements[0];
large = twoThreeNode.elements[1];
}
else if (element > twoThreeNode.elements[1])
{
small = twoThreeNode.elements[0];
middle = twoThreeNode.elements[1];
large = element;
}
else
{
small = twoThreeNode.elements[0];
middle = element;
large = twoThreeNode.elements[1];
}
n1.elements[0] = small;
n2.elements[0] = large;
n1.parent = p;
n2.parent = p;
if (p.NumberOfElements() == 0)
{
p.children[0] = n1;
p.children[1] = n2;
root = p;
n1.isLeaf = true;
n2.isLeaf = true;
}
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;
}
n1.isLeaf = true;
n2.isLeaf = true;
}
else
{
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[0] > p.elements[0] && n1.elements[0] > 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;
}
}
if (twoThreeNode.IsLeaf() == false)
{
twoThreeNode.children[0].parent = n1;
twoThreeNode.children[1].parent = n1;
twoThreeNode.children[2].parent = n2;
twoThreeNode.children[3].parent = n2;
n1.children[0] = twoThreeNode.children[0];
n1.children[1] = twoThreeNode.children[1];
n2.children[0] = twoThreeNode.children[2];
n2.children[1] = twoThreeNode.children[3];
n1.isLeaf = false;
n2.isLeaf = false;
}
if (p.NumberOfElements() == 2)
{
Split(p, middle);
if (n1.children[0] != null || n2.children[0] != null)
{
if (n1.children[0].IsLeaf() || n2.children[0].IsLeaf())
{
n1.isLeaf = false;
n2.isLeaf = false;
}
}
else
{
n1.isLeaf = true;
n2.isLeaf = true;
}
n1.parent.isLeaf = false;
n2.parent.isLeaf = false;
}
else if (p.NumberOfElements() == 1)
{
if (p.elements[0] < middle)
{
p.elements[1] = middle;
}
else
{
p.elements[1] = p.elements[0];
p.elements[0] = middle;
}
}
else
{
p.elements[0] = middle;
}
}
public TwoThreeTree()
{
root = new TwoThreeTreeNode();
limit = 2;
initRoot();
}
public TwoThreeTreeNode()
{
elements = new int[2];
children = new TwoThreeTreeNode[4];
}