/// <summary>
/// do a right rotation
/// </summary>
/// <param name="rightSibling"></param>
/// <param name="leftSibling"></param>
private void rightRotate(BPTreeNode <T> leftSibling, BPTreeNode <T> rightSibling)
{
var parentIndex = getNextSeparatorIndex(leftSibling);
//move parent value to right
InsertAt(rightSibling.Keys, 0, rightSibling.Parent.Keys[parentIndex]);
rightSibling.KeyCount++;
insertChild(rightSibling, 0, leftSibling.Children[leftSibling.KeyCount]);
if (rightSibling.Children[1] != null &&
rightSibling.Children[1].IsLeaf)
{
rightSibling.Keys[0] = rightSibling.Children[1].Keys[0];
}
//move rightmost element in left sibling to parent
rightSibling.Parent.Keys[parentIndex] = leftSibling.Keys[leftSibling.KeyCount - 1];
//remove rightmost element of left sibling
removeAt(leftSibling.Keys, leftSibling.KeyCount - 1);
leftSibling.KeyCount--;
removeChild(leftSibling, leftSibling.KeyCount + 1);
if (rightSibling.IsLeaf)
{
rightSibling.Keys[0] = rightSibling.Parent.Keys[parentIndex];
}
}
/// <summary>
/// Locate the node in which the item to delete exist
/// </summary>
/// <param name="node"></param>
/// <param name="value"></param>
/// <returns></returns>
private BPTreeNode <T> findDeletionNode(BPTreeNode <T> node, T value)
{
//if leaf then its time to insert
if (node.IsLeaf)
{
for (int i = 0; i < node.KeyCount; i++)
{
if (value.CompareTo(node.Keys[i]) == 0)
{
return(node);
}
}
}
else
{
//if not leaf then drill down to leaf
for (int i = 0; i < node.KeyCount; i++)
{
//current value is less than new value
//drill down to left child of current value
if (value.CompareTo(node.Keys[i]) < 0)
{
return(findDeletionNode(node.Children[i], value));
}
//current value is grearer than new value
//and current value is last element
else if (node.KeyCount == i + 1)
{
return(findDeletionNode(node.Children[i + 1], value));
}
}
}
return(null);
}
/// <summary>
/// do a left rotation
/// </summary>
/// <param name="leftSibling"></param>
/// <param name="rightSibling"></param>
private void leftRotate(BPTreeNode <T> leftSibling, BPTreeNode <T> rightSibling)
{
var parentIndex = getNextSeparatorIndex(leftSibling);
//move root to left
leftSibling.Keys[leftSibling.KeyCount] = leftSibling.Parent.Keys[parentIndex];
leftSibling.KeyCount++;
setChild(leftSibling, leftSibling.KeyCount, rightSibling.Children[0]);
if (leftSibling.Children[leftSibling.KeyCount] != null &&
leftSibling.Children[leftSibling.KeyCount].IsLeaf)
{
leftSibling.Keys[leftSibling.KeyCount - 1] = leftSibling.Children[leftSibling.KeyCount].Keys[0];
}
//move right to parent
leftSibling.Parent.Keys[parentIndex] = rightSibling.Keys[0];
//remove right
removeAt(rightSibling.Keys, 0);
rightSibling.KeyCount--;
removeChild(rightSibling, 0);
if (rightSibling.IsLeaf)
{
rightSibling.Parent.Keys[parentIndex] = rightSibling.Keys[0];
}
if (leftSibling.IsLeaf && leftSibling.Parent.Children[0] != leftSibling)
{
parentIndex = getPrevSeparatorIndex(leftSibling);
leftSibling.Parent.Keys[parentIndex] = leftSibling.Keys[0];
}
}
/// <summary>
/// optionally recursively update outdated index with new min of right node
/// after deletion of a value
/// </summary>
/// <param name="node"></param>
/// <param name="deleteKey"></param>
/// <param name="nextMin"></param>
private void updateIndex(BPTreeNode <T> node, T deleteKey, bool spiralUp)
{
if (node == null)
{
return;
}
if (node.IsLeaf || node.Children[0].IsLeaf)
{
updateIndex(node.Parent, deleteKey, spiralUp);
return;
}
for (int i = 0; i < node.KeyCount; i++)
{
if (node.Keys[i].CompareTo(deleteKey) == 0)
{
node.Keys[i] = findMinNode(node.Children[i + 1]).Keys[0];
}
}
if (spiralUp)
{
updateIndex(node.Parent, deleteKey, true);
}
}
/// <summary>
/// get left sibling node
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
private BPTreeNode <T> getLeftSibling(BPTreeNode <T> node)
{
if (node.Index == 0)
{
return(null);
}
return(node.Parent.Children[node.Index - 1]);
}
private void setChild(BPTreeNode <T> parent, int childIndex, BPTreeNode <T> child)
{
parent.Children[childIndex] = child;
if (child != null)
{
child.Parent = parent;
child.Index = childIndex;
}
}
/// <summary>
/// return the node containing min value which will be a leaf at the left most
/// </summary>
/// <param name="AsBPTreeNode"></param>
/// <returns></returns>
private BPTreeNode <T> findMinNode(BPTreeNode <T> node)
{
//if leaf return node
if (node.IsLeaf)
{
return(node);
}
//step in to left most child
return(findMinNode(node.Children[0]));
}
/// <summary>
/// get the right sibling node
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
private BPTreeNode <T> getRightSibling(BPTreeNode <T> node)
{
var parent = node.Parent;
if (node.Index == parent.KeyCount)
{
return(null);
}
return(parent.Children[node.Index + 1]);
}
/// <summary>
/// return the node containing max value which will be a leaf at the right most
/// </summary>
/// <param name="AsBPTreeNode"></param>
/// <returns></returns>
private BPTreeNode <T> findMaxNode(BPTreeNode <T> node)
{
//if leaf return node
if (node.IsLeaf)
{
return(node);
}
//step in to right most child
return(findMaxNode(node.Children[node.KeyCount]));
}
private void removeChild(BPTreeNode <T> parent, int childIndex)
{
removeAt(parent.Children, childIndex);
//update indices
for (int i = childIndex; i <= parent.KeyCount; i++)
{
if (parent.Children[i] != null)
{
parent.Children[i].Index = i;
}
}
}
public bool MoveNext()
{
if (i + 1 < current.KeyCount)
{
i++;
return(true);
}
current = current.Next;
i = 0;
return(current != null && current.KeyCount > 0);
}
/// <summary>
/// Balance a node which is short of Keys by rotations or merge
/// </summary>
/// <param name="node"></param>
private void balance(BPTreeNode <T> node, T deleteKey)
{
if (node == Root)
{
return;
}
if (node.KeyCount >= minKeysPerNode)
{
updateIndex(node, deleteKey, true);
return;
}
var rightSibling = getRightSibling(node);
if (rightSibling != null &&
(rightSibling.KeyCount) > minKeysPerNode)
{
leftRotate(node, rightSibling);
var minNode = findMinNode(node);
updateIndex(node, deleteKey, true);
return;
}
var leftSibling = getLeftSibling(node);
if (leftSibling != null &&
(leftSibling.KeyCount) > minKeysPerNode)
{
rightRotate(leftSibling, node);
updateIndex(node, deleteKey, true);
return;
}
if (rightSibling != null)
{
sandwich(node, rightSibling, deleteKey);
}
else
{
sandwich(leftSibling, node, deleteKey);
}
}
/// <summary>
/// Inserts and element to B-Tree
/// </summary>
/// <param name="newValue"></param>
public void Insert(T newValue)
{
if (Root == null)
{
Root = new BPTreeNode <T>(maxKeysPerNode, null);
Root.Keys[0] = newValue;
Root.KeyCount++;
Count++;
BottomLeftNode = Root;
return;
}
var leafToInsert = findInsertionLeaf(Root, newValue);
insertAndSplit(ref leafToInsert, newValue, null, null);
Count++;
}
/// <summary>
/// Get next separator key of this child Node in parent
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
private int getNextSeparatorIndex(BPTreeNode <T> node)
{
var parent = node.Parent;
if (node.Index == 0)
{
return(0);
}
else if (node.Index == parent.KeyCount)
{
return(node.Index - 1);
}
else
{
return(node.Index);
}
}
private void insertChild(BPTreeNode <T> parent, int childIndex, BPTreeNode <T> child)
{
InsertAt(parent.Children, childIndex, child);
if (child != null)
{
child.Parent = parent;
}
//update indices
for (int i = childIndex; i <= parent.KeyCount; i++)
{
if (parent.Children[i] != null)
{
parent.Children[i].Index = i;
}
}
}
/// <summary>
/// Insert to a node that is not full
/// </summary>
/// <param name="node"></param>
/// <param name="newValue"></param>
/// <param name="newValueLeft"></param>
/// <param name="newValueRight"></param>
private void insertNonFullNode(ref BPTreeNode <T> node, T newValue,
BPTreeNode <T> newValueLeft, BPTreeNode <T> newValueRight)
{
var inserted = false;
//if left is not null
//then right should'nt be null
if (newValueLeft != null)
{
newValueLeft.Parent = node;
newValueRight.Parent = node;
}
//insert in sorted order
for (int i = 0; i < node.KeyCount; i++)
{
if (newValue.CompareTo(node.Keys[i]) < 0)
{
InsertAt(node.Keys, i, newValue);
node.KeyCount++;
//Insert children if any
setChild(node, i, newValueLeft);
insertChild(node, i + 1, newValueRight);
inserted = true;
break;
}
}
//newValue is the greatest
//element should be inserted at the end then
if (!inserted)
{
node.Keys[node.KeyCount] = newValue;
node.KeyCount++;
setChild(node, node.KeyCount - 1, newValueLeft);
setChild(node, node.KeyCount, newValueRight);
}
}
public BPTreeEnumerator(BPTree <T> tree)
{
bottomLeftNode = tree.BottomLeftNode;
current = bottomLeftNode;
}
public void Reset()
{
current = bottomLeftNode;
i = -1;
}
public void Dispose()
{
current = null;
bottomLeftNode = null;
i = -1;
}
internal BPTreeNode(int maxKeysPerNode, BPTreeNode <T> parent)
: base(maxKeysPerNode)
{
Parent = parent;
Children = new BPTreeNode <T> [maxKeysPerNode + 1];
}
/// <summary>
/// Insert and split recursively up until no split is required
/// </summary>
/// <param name="node"></param>
/// <param name="newValue"></param>
private void insertAndSplit(ref BPTreeNode <T> node, T newValue,
BPTreeNode <T> newValueLeft, BPTreeNode <T> newValueRight)
{
//add new item to current node
//this increases the height of B+ tree by one by adding a new root at top
if (node == null)
{
node = new BPTreeNode <T>(maxKeysPerNode, null);
Root = node;
}
//if node is full
//then split node
//and insert new median to parent
if (node.KeyCount == maxKeysPerNode)
{
//divide the current node values + new Node as left & right sub nodes
var left = new BPTreeNode <T>(maxKeysPerNode, null);
var right = new BPTreeNode <T>(maxKeysPerNode, null);
//connect leaves via linked list for faster enumeration
if (node.IsLeaf)
{
left.Next = right;
right.Prev = left;
if (node.Next != null)
{
right.Next = node.Next;
node.Next.Prev = right;
}
if (node.Prev != null)
{
left.Prev = node.Prev;
node.Prev.Next = left;
}
else
{
//left most bottom node
BottomLeftNode = left;
}
}
//median of current Node
var currentMedianIndex = node.GetMedianIndex();
//init currentNode under consideration to left
var currentNode = left;
var currentNodeIndex = 0;
//new Median also takes new Value in to Account
var newMedian = default(T);
var newMedianSet = false;
var newValueInserted = false;
//keep track of each insertion
int insertionCount = 0;
//insert newValue and existing values in sorted order
//to left & right nodes
//set new median during sorting
for (int i = 0; i < node.KeyCount; i++)
{
//if insertion count reached new median
//set the new median by picking the next smallest value
if (!newMedianSet && insertionCount == currentMedianIndex)
{
newMedianSet = true;
//median can be the new value or node.keys[i] (next node key)
//whichever is smaller
if (!newValueInserted && newValue.CompareTo(node.Keys[i]) < 0)
{
//median is new value
newMedian = newValue;
newValueInserted = true;
if (newValueLeft != null)
{
setChild(currentNode, currentNode.KeyCount, newValueLeft);
}
//now fill right node
currentNode = right;
currentNodeIndex = 0;
if (newValueRight != null)
{
setChild(currentNode, 0, newValueRight);
}
i--;
insertionCount++;
continue;
}
else
{
//median is next node
newMedian = node.Keys[i];
//now fill right node
currentNode = right;
currentNodeIndex = 0;
continue;
}
}
//pick the smaller among newValue & node.Keys[i]
//and insert in to currentNode (left & right nodes)
//if new Value was already inserted then just copy from node.Keys in sequence
//since node.Keys is already in sorted order it should be fine
if (newValueInserted || node.Keys[i].CompareTo(newValue) < 0)
{
currentNode.Keys[currentNodeIndex] = node.Keys[i];
currentNode.KeyCount++;
//if child is set don't set again
//the child was already set by last newValueRight or last node
if (currentNode.Children[currentNodeIndex] == null)
{
setChild(currentNode, currentNodeIndex, node.Children[i]);
}
setChild(currentNode, currentNodeIndex + 1, node.Children[i + 1]);
}
else
{
currentNode.Keys[currentNodeIndex] = newValue;
currentNode.KeyCount++;
setChild(currentNode, currentNodeIndex, newValueLeft);
setChild(currentNode, currentNodeIndex + 1, newValueRight);
i--;
newValueInserted = true;
}
currentNodeIndex++;
insertionCount++;
}
//could be that thew newKey is the greatest
//so insert at end
if (!newValueInserted)
{
currentNode.Keys[currentNodeIndex] = newValue;
currentNode.KeyCount++;
setChild(currentNode, currentNodeIndex, newValueLeft);
setChild(currentNode, currentNodeIndex + 1, newValueRight);
}
if (node.IsLeaf)
{
InsertAt(right.Keys, 0, newMedian);
right.KeyCount++;
}
//insert overflow element (newMedian) to parent
var parent = node.Parent;
insertAndSplit(ref parent, newMedian, left, right);
}
//newValue have room to fit in this node
//so just insert in right spot in asc order of keys
else
{
insertNonFullNode(ref node, newValue, newValueLeft, newValueRight);
}
}
/// <summary>
/// merge two adjacent siblings to one node
/// </summary>
/// <param name="leftSibling"></param>
/// <param name="rightSibling"></param>
/// <param name="deleteKey"></param>
private void sandwich(BPTreeNode <T> leftSibling, BPTreeNode <T> rightSibling, T deleteKey)
{
var separatorIndex = getNextSeparatorIndex(leftSibling);
var parent = leftSibling.Parent;
var newNode = new BPTreeNode <T>(maxKeysPerNode, leftSibling.Parent);
//if leaves are merged then update the Next & Prev pointers
if (leftSibling.IsLeaf)
{
if (leftSibling.Prev != null)
{
newNode.Prev = leftSibling.Prev;
leftSibling.Prev.Next = newNode;
}
else
{
BottomLeftNode = newNode;
}
if (rightSibling.Next != null)
{
newNode.Next = rightSibling.Next;
rightSibling.Next.Prev = newNode;
}
}
var newIndex = 0;
for (int i = 0; i < leftSibling.KeyCount; i++)
{
newNode.Keys[newIndex] = leftSibling.Keys[i];
if (leftSibling.Children[i] != null)
{
setChild(newNode, newIndex, leftSibling.Children[i]);
}
if (leftSibling.Children[i + 1] != null)
{
setChild(newNode, newIndex + 1, leftSibling.Children[i + 1]);
}
newIndex++;
}
//special case when left sibling is empty
if (leftSibling.KeyCount == 0 && leftSibling.Children[0] != null)
{
setChild(newNode, newIndex, leftSibling.Children[0]);
}
if (!rightSibling.IsLeaf)
{
newNode.Keys[newIndex] = parent.Keys[separatorIndex];
newIndex++;
}
for (int i = 0; i < rightSibling.KeyCount; i++)
{
newNode.Keys[newIndex] = rightSibling.Keys[i];
if (rightSibling.Children[i] != null)
{
setChild(newNode, newIndex, rightSibling.Children[i]);
//when a left leaf is added as right leaf
//we need to push parent key as first node of new leaf
if (i == 0 && rightSibling.Children[i].IsLeaf &&
rightSibling.Children[i].Keys[0].CompareTo(newNode.Keys[newIndex - 1]) != 0)
{
InsertAt(rightSibling.Children[i].Keys, 0, newNode.Keys[newIndex - 1]);
rightSibling.Children[i].KeyCount++;
}
}
if (rightSibling.Children[i + 1] != null)
{
setChild(newNode, newIndex + 1, rightSibling.Children[i + 1]);
}
newIndex++;
}
//special case when left sibling is empty
if (rightSibling.KeyCount == 0 && rightSibling.Children[0] != null)
{
setChild(newNode, newIndex, rightSibling.Children[0]);
if (newNode.Children[newIndex].IsLeaf)
{
newNode.Keys[newIndex - 1] = newNode.Children[newIndex].Keys[0];
}
}
newNode.KeyCount = newIndex;
setChild(parent, separatorIndex, newNode);
removeAt(parent.Keys, separatorIndex);
parent.KeyCount--;
removeChild(parent, separatorIndex + 1);
if (newNode.IsLeaf && newNode.Parent.Children[0] != newNode)
{
separatorIndex = getPrevSeparatorIndex(newNode);
newNode.Parent.Keys[separatorIndex] = newNode.Keys[0];
}
updateIndex(newNode, deleteKey, false);
if (parent.KeyCount == 0 &&
parent == Root)
{
Root = newNode;
Root.Parent = null;
if (Root.KeyCount == 0)
{
Root = null;
}
return;
}
if (parent.KeyCount < minKeysPerNode)
{
balance(parent, deleteKey);
}
updateIndex(newNode, deleteKey, true);
}