void moveParent(Bnode parent, int position, Bnode child)
{
parent.children[position] = child;
if (child != null)
{
child.parent = parent;
}
}
void leftRotate(Bnode parent, int position)
{
Bnode left = parent.children[position];
Bnode right = parent.children[position + 1];
int newPosition = left.insert(parent.keys[position]);
moveParent(left, newPosition + 1, right.children[0]);
parent.keys[position] = right.keys[0];
right.children[0] = right.children[1];
right.delete(0);
}
public int findChild(Bnode child)
{
for (int i = 0; i <= n; i++)
{
if (children[i] == child)
{
return(i);
}
}
return(-1); //not found
}
public void getNodeCount(ref Bnode root)
{
if (root != null)
{
nodeCount++;
for (int i = 0; i < root.n + 1; i++)
{
getNodeCount(ref root.children[i]);
}
}
}
public Bnode(int m) //,int depth)
{ //m is order of multiway tree
this.size = m - 1;
this.n = 0;
this.keys = new int[this.size + 1]; //may overflow 1 key
this.children = new Bnode[this.size + 2];
this.children[0] = null;
this.parent = null;
//this.depth = depth;
}
void rightRotate(Bnode parent, int position)
{
Bnode left = parent.children[position];
Bnode right = parent.children[position + 1];
int newPosition = right.insert(parent.keys[position]);
right.children[1] = right.children[0];
moveParent(right, newPosition, left.children[left.n]);
parent.keys[position] = left.keys[left.n - 1];
left.n--;
}
public void inorder(ref Bnode root)
{
if (root != null)
{
for (int i = 0; i < root.n; i++)
{
inorder(ref root.children[i]);
Console.WriteLine("Keys : " + root.keys[i] + " n : " + root.n + " parent.keys[0] : " + (root.parent == null ? "-" : root.parent.keys[0].ToString())); // used when you're not sure visualization is correct
}
inorder(ref root.children[root.n]);
}
}
public void getMaxDepth(ref Bnode root, int depth = 0)
{
if (root != null)
{
if (depth > maxDepth)
{
maxDepth = depth;
}
for (int i = 0; i < root.n; i++)
{
getMaxDepth(ref root.children[i], depth + 1);
}
}
}
Bnode merge(Bnode parent, int position)
{
Bnode left = parent.children[position];
Bnode right = parent.children[position + 1];
int newPosition = left.insert(parent.keys[position]);
moveParent(left, newPosition + 1, right.children[0]);
for (int i = 0; i < right.n; i++)
{
newPosition = left.insert(right.keys[i]);
moveParent(left, newPosition + 1, right.children[i + 1]);
}
parent.delete(position);
return(left);
}
public void getFakeBNodes(ref Bnode root, int parentIndex = -1, int traverseWay = -1, int depth = 0)
{
if (root != null)
{
int nodeIndex = nodeCtr;
nodeCtr++;
// set traverse index
if (parentIndex == -1)
{
traverseIndex[nodeIndex] = new int[1];
traverseIndex[nodeIndex][0] = -1;
}
else
{
if (traverseIndex[parentIndex][0] == -1)
{
traverseIndex[nodeIndex] = new int[1];
traverseIndex[nodeIndex][0] = traverseWay;
}
else
{
traverseIndex[nodeIndex] = new int[traverseIndex[parentIndex].Count() + 1];
for (int i = 0; i < traverseIndex[parentIndex].Count(); i++)
{
traverseIndex[nodeIndex][i] = traverseIndex[parentIndex][i];
}
traverseIndex[nodeIndex][traverseIndex[nodeIndex].Count() - 1] = traverseWay;
}
}
// get childCount & recursive
int childCount = 0;
for (int i = 0; i < root.n + 1; i++)
{
if (root.children[i] != null)
{
childCount++;
getFakeBNodes(ref root.children[i], nodeIndex, i, depth + 1);
}
}
// add to fakeBNodes
fakeBNodes.Add(new FakeBNode(depth, root.n, root.keys, traverseIndex[nodeIndex], childCount));
}
}
public Node find(Bnode root, int key)
{
Bnode current = root;
while (current != null)
{
int position = current.findPosition(key);
if (position < current.n && current.keys[position] == key)
{
return(new Node(current, position)); //found
}
else
{
current = current.children[position];
}
}
return(null); //not found
}
public void delete(ref Bnode root, int key)
{
Node current = find(root, key);
if (current != null)
{
if (current.multiNode.children[current.position] != null)
{
//current is not leaf
//..
//find in-order predecessor
Bnode predecessor =
current.multiNode.children[current.position];
while (predecessor.children[predecessor.n] != null)
{
predecessor = predecessor.children[predecessor.n];
}
//...
//replace with the predecessor
current.multiNode.keys[current.position] =
predecessor.keys[predecessor.n - 1];
//try to delete leaf
current = new Node(predecessor, predecessor.n - 1);
}
//delete leaf
//...
current.multiNode.delete(current.position);
int minKeys = current.multiNode.size / 2;
if (current.multiNode == root && current.multiNode.n == 0)
{
root = null;
}
while (root != null && current.multiNode != root && current.multiNode.n < minKeys) //underflow
{
rebalanceAfterDeletion(ref root, ref current.multiNode, minKeys);
}
}
}
bool rebalanceAfterDeletion(ref Bnode root, ref Bnode current, int minKeys)
{
Bnode parent = current.parent;
int i = parent.findChild(current);
//case 1: look at left sibling
if (i > 0 && parent.children[i - 1].n > minKeys)
{
rightRotate(parent, i - 1);
return(true);
}
//case 2: look at right sibling
if (i > parent.n && parent.children[i + 1].n > minKeys)
{
leftRotate(parent, i);
return(true);
}
//...
//merge
if (i > 0)
{
current = merge(parent, i - 1); //case 3: merge to left sibling
}
else
{
current = merge(parent, i); //case 3: merge to right sibling
}
if (parent.n == 0 && parent == root)
{
root = current;
current.parent = null;
}
else
{
current = parent;
}
return(false);
}
public List <int> getFindTraverseIndex(Bnode root, int key)
{
Bnode current = root;
List <int> searchTraverseIndex = new List <int>();
while (current != null)
{
int position = current.findPosition(key);
if (position < current.n && current.keys[position] == key)
{
if (current == this.root)
{
searchTraverseIndex.Add(-1);
}
return(searchTraverseIndex); //found
}
else
{
current = current.children[position];
searchTraverseIndex.Add(position);
}
}
return(null); //not found
}
public void insert(ref Bnode root, int key)
{
int currentDepth = 0;
if (root == null)
{
root = new Bnode(m);//,0);
root.insert(key);
}
else
{
Bnode current = root;
while (true)
{
if (current.children[0] == null) //insert must be in leaf
{
int position = current.insert(key);
while (current.n > current.size) //overflow
//split the node
{
Object[] result = split(ref root, current, currentDepth);
//try to insert middle key to parent
Bnode newNode = (Bnode)result[0];
key = (int)result[1]; //separator
current = current.parent;
position = current.insert(key);
current.children[position + 1] = newNode;
}
break;
}
current = current.children[current.findPosition(key)];
currentDepth++;
}
}
}
// other
Object[] split(ref Bnode root, Bnode node, int currentDepth)
{
int mid = node.n / 2;
if (node.parent == null)
{
root = new Bnode(m);//, currentDepth);
root.children[0] = node;
node.parent = root;
}
Bnode newNode = new Bnode(m);//, currentDepth);
newNode.parent = node.parent;
int nk = 0;
for (int k = mid + 1; k < node.n; k++, nk++)
{
newNode.insert(node.keys[k]);
moveParent(newNode, nk, node.children[k]);
}
moveParent(newNode, nk, node.children[node.n]);
node.n = mid;
return(new Object[] { newNode, node.keys[mid] });
}
// CODE
#region
public Btree(int m)
{
root = new Bnode(m);//,0);
this.m = m;
}