/// <summary>
/// Transplants one subtree with another subtree.
/// </summary>
/// <param name="first"> First subtree.</param>
/// <param name="second"> Second subtree.</param>
private void Transplant(NodeRB <TKey, TValue> firstSubTree, NodeRB <TKey, TValue> secondSubTree)
{
//if first subtree has no parent then make the second subtree the root of the tree
if (firstSubTree.Parent == nilNode)
{
this.root = secondSubTree;
}
//else if first subtree is a left child
//then make second subtree the left child of first subtree's parent
else if (firstSubTree == firstSubTree.Parent.Left)
{
firstSubTree.Parent.Left = secondSubTree;
}
//otherwise if first subtree is a right child
//then make second subtree the right child of first subtree's parent
else
{
firstSubTree.Parent.Right = secondSubTree;
}
//first subtree's parent becomes second subtree's parent
secondSubTree.Parent = firstSubTree.Parent;
}
/// <summary>
/// Gets the node with the passed key,if it exists.
/// </summary>
/// <param name="key"> Key. </param>
/// <returns> Returns the node with the specified key,if it exist,and null;otherwise.</returns>
private NodeRB <TKey, TValue> GetRBNode(TKey key)
{
//variable for storing CompareTo value
int comparison;
NodeRB <TKey, TValue> tempNode = this.root;
while (tempNode != nilNode)
{
//comparing keys
comparison = key.CompareTo(tempNode.Key);
//if the key is greater go to the right
if (comparison > 0)
{
tempNode = tempNode.Right;
}
//else if key is less then go to the left
else if (comparison < 0)
{
tempNode = tempNode.Left;
}
//if key is equal to tempNode key then the node is found
//return the found node
else
{
return(tempNode);
}
}
//return null if the node with the given key is not found
return(null);
}
/// <summary>
/// Creates new instance of red-black tree node
/// </summary>
/// <param name="key"> Key of node.</param>
/// <param name="value"> Value of node.</param>
/// <param name="color"> Color of node.</param>
/// <param name="parent"> Parent of node.</param>
/// <param name="left"> Left child of node.</param>
/// <param name="right"> Right child of node.</param>
public NodeRB(TKey key, TValue value, NodeColor color = NodeColor.Black,
NodeRB <TKey, TValue> parent = null, NodeRB <TKey, TValue> left = null, NodeRB <TKey, TValue> right = null)
{
this.Key = key;
this.Value = value;
this.Color = color;
this.Left = left;
this.Right = right;
this.Parent = parent;
}
/// <summary>
/// Gets the element containing minimum key in the given subtree.
/// </summary>
/// <param name="node"> Node.</param>
/// <returns> Returns the element containing minimum key in the given subtree. </returns>
private static NodeRB <TKey, TValue> MinimumKeyNode(NodeRB <TKey, TValue> node)
{
NodeRB <TKey, TValue> temp = node;
//moving to the leftmost node in the given tree
//because in binary search tree the minimal key is in the leftmost node
while (temp.Left != nilNode)
{
temp = temp.Left;
}
return(temp);
}
/// <summary>
/// Gets the collection of all elements in the dictionary.
/// </summary>
/// <returns> Returns the collection of all elements in the dictionary.</returns>
private List <NodeRB <TKey, TValue> > GetAllElements()
{
List <NodeRB <TKey, TValue> > list = new List <NodeRB <TKey, TValue> >();
NodeRB <TKey, TValue> tempNode = this.root, predecessor;
//doing inorder traversal using James Hiram Morris algorithm
while (tempNode != nilNode)
{
//if the node's left child is nilNode
//then add node to collection and move to the right
if (tempNode.Left == nilNode)
{
list.Add(tempNode);
tempNode = tempNode.Right;
}
//otherwise need to find the inorder predecessor of the tempNode
else
{
predecessor = tempNode.Left;
while (predecessor.Right != nilNode && predecessor.Right != nilNode)
{
predecessor = predecessor.Right;
}
//if inorder predecessor doesn't have right child then make tempNode its right child
if (predecessor.Right == nilNode)
{
predecessor.Right = tempNode;
tempNode = tempNode.Left;
}
//if predecessor has right child than add it to the list
//and move to the right
else
{
predecessor.Right = nilNode;
list.Add(tempNode);
tempNode = tempNode.Right;
}
}
}
//return the list containing dictionary elements.
return(list);
}
/// <summary>
/// Stores the value of the element with the given key in the value parameter
/// if corresponding element exists in the dictionary.
/// </summary>
/// <param name="key"> Key.</param>
/// <param name="value"> Value.</param>
/// <returns> Returns false if the element with the given key exists in the dictionary and false;otherwise.</returns>
public bool TryGetValue(TKey key, out TValue value)
{
NodeRB <TKey, TValue> node = this.GetRBNode(key);
//if node is found then set the value and return true
if (node != null)
{
value = node.Value;
return(true);
}
//otherwise return false
else
{
value = default(TValue);
return(false);
}
}
/// <summary>
/// Rotates the tree starting with the given subtree to the left.
/// </summary>
/// <param name="node"> Node.</param>
private void LeftRotate(NodeRB <TKey, TValue> node)
{
//setting the Right child of node to temp
NodeRB <TKey, TValue> temp = node.Right;
//temp's left child becomes the right child of node
node.Right = temp.Left;
//if the right child of node has left child
if (temp.Left != nilNode)
{
temp.Left.Parent = node;
}
temp.Parent = node.Parent;
//if node doesn't have parent then right child of node becomes the root of tree
if (node.Parent == nilNode)
{
this.root = temp;
}
//else if node is a left child then right child of node becomes the
//left child of node's parent
else if (node == node.Parent.Left)
{
node.Parent.Left = temp;
}
//otherwise becomes right child
else
{
node.Parent.Right = temp;
}
//putting node on the left of temp
temp.Left = node;
node.Parent = temp;
}
/// <summary>
/// Gets or sets the value of the element with the given key.
/// </summary>
/// <param name="key"> Key.</param>
/// <returns> Returns value.</returns>
public TValue this[TKey key]
{
//gets the value with the specified key
get
{
NodeRB <TKey, TValue> node = this.GetRBNode(key);
//if element is found return the value
if (node != null)
{
return(node.Value);
}
//else throw exception
else
{
throw new KeyNotFoundException("Element with the given key doesn't exist in the dictioanry.");
}
}
//sets the value
set
{
NodeRB <TKey, TValue> node = this.GetRBNode(key);
//if the element is found then set the value
if (node != null)
{
node.Value = value;
}
//else throw an exception
else
{
this.Insert(key, value);
}
}
}
/// <summary>
/// Rotates the tree with the given subtree to the right
/// </summary>
/// <param name="node"></param>
private void RightRotate(NodeRB <TKey, TValue> node)
{
//setting the left child of node to temp
NodeRB <TKey, TValue> temp = node.Left;
//temp's right child becomes the left child of node
node.Left = temp.Right;
//if the left child of node doesn't have right child
if (temp.Right != nilNode)
{
temp.Right.Parent = node;
}
temp.Parent = node.Parent;
//if node doesn't have parent then left child of node becomes the root of the tree
if (node.Parent == nilNode)
{
this.root = temp;
}
//else if node is a right child
else if (node == node.Parent.Right)
{
node.Parent.Right = temp;
}
//otherwis if node is a left child
else
{
node.Parent.Left = temp;
}
//putting node on the right of its left child
temp.Left = node;
node.Parent = temp;
}
/// <summary>
/// Fixes the red-black tree after deletion of a node.
/// </summary>
/// <param name="node"> Node. </param>
private void DeleteFixup(NodeRB <TKey, TValue> fixupNode)
{
NodeRB <TKey, TValue> temp;
//iterating all over the tree to fix up
while (fixupNode != this.root && fixupNode.Color == NodeColor.Black)
{
//if fixupNode is a left child
if (fixupNode == fixupNode.Parent.Left)
{
//save the sibling of fixupNode
temp = fixupNode.Parent.Right;
//if the color of fixupNode's sibling is red
if (temp.Color == NodeColor.Red)
{
//make the sibling's color black,parent's color - red
temp.Color = NodeColor.Black;
fixupNode.Parent.Color = NodeColor.Red;
//rotate the subtree starting with the parent of fixupNode
this.LeftRotate(fixupNode.Parent);
//update the sibling
temp = fixupNode.Parent.Right;
}
if (temp == nilNode)
{
return;
}
//if (temp != nilNode)
//if both of temp's children are black
if (temp.Left.Color == NodeColor.Black && temp.Right.Color == NodeColor.Black)
{
temp.Color = NodeColor.Red;
//continue with the parent
fixupNode = fixupNode.Parent;
}
//if only the right child of temp is black
else
{
if (temp.Right.Color == NodeColor.Black)
{
//update colors
temp.Left.Color = NodeColor.Black;
temp.Color = NodeColor.Red;
//rotate the subtree starting with temp
this.RightRotate(temp);
//update temp
temp = fixupNode.Parent.Right;
}
//otherwise
//update colors
temp.Color = fixupNode.Parent.Color;
fixupNode.Parent.Color = temp.Right.Color = NodeColor.Black;
//rotate the subtree starting with the parent of fixupNode
this.LeftRotate(fixupNode.Parent);
//store root in temp
temp = this.root;
}
}
//otherwise if fixupNode is a right child
//doing the same only exchanging right and left because here we have symmetry
else
{
temp = fixupNode.Parent.Left;
if (temp == nilNode)
{
return;
}
//if sibling of fixupNode is red
if (temp.Color == NodeColor.Red)
{
//update colors
temp.Color = NodeColor.Black;
fixupNode.Parent.Color = NodeColor.Red;
//rotate to the right starting with the parent
this.RightRotate(fixupNode.Parent);
//update sibling
temp = fixupNode.Parent.Left;
}
//if the sibling's children are black
if (temp.Left.Color == NodeColor.Black && temp.Right.Color == NodeColor.Black)
{
temp.Color = NodeColor.Red;
fixupNode = fixupNode.Parent;
}
//if only the left child of sibling is black
else
{
if (temp.Left.Color == NodeColor.Black)
{
//update colors
temp.Right.Color = NodeColor.Black;
temp.Color = NodeColor.Red;
//rotate the subtree starting with the sibling
this.LeftRotate(temp);
//update sibling
temp = fixupNode.Parent.Left;
}
//setting colors
temp.Color = fixupNode.Parent.Color;
fixupNode.Parent.Color = temp.Left.Color = NodeColor.Black;
//rotate the subtree starting with sibling
this.RightRotate(temp);
//update sibling
temp = this.root;
}
}
temp.Color = NodeColor.Black;
}
}
/// <summary>
/// Deletes the element with specified key from the dictionary if it exists there.
/// </summary>
/// <param name="key"> Key.</param>
private bool Delete(TKey key)
{
NodeRB <TKey, TValue> node = this.GetRBNode(key);
//if there is no element with the given key then return
if (node == null)
{
return(false);
}
//if the node is found then delete
NodeRB <TKey, TValue> temp = node, fixupNode;
NodeColor tempInitialColor = temp.Color;
//if node doesn't have left child
if (node.Left == nilNode)
{
//fixupNode becomes the same as the node's right child
fixupNode = node.Right;
//transplant node and node's right child
this.Transplant(node, node.Right);
}
//else if node has left child but doesn't have right child
else if (node.Right == nilNode)
{
//make fixupNode node's left child
fixupNode = node.Left;
//transplant node and node's left child
this.Transplant(node, node.Left);
}
//otherwise if node have 2 children
else
{
//temp becomes the same as the leftmost node of node's righ subtree
temp = MinimumKeyNode(node.Right);
//update tempInitialColor
tempInitialColor = temp.Color;
//update fixupNode
fixupNode = temp.Right;
//if node is the right child of updated temp
//make temp the parent of updated fixupNode
if (temp.Parent == node)
{
fixupNode.Parent = temp;
}
//otherwise
else
{
//transplant temp and the right child of temp
this.Transplant(temp, temp.Right);
//the right child of node becomes the right child of temp
temp.Right = node.Right;
//temp becomes the parent of temp right
temp.Right.Parent = temp;
}
//transplant node and temp subtrees
this.Transplant(node, temp);
//update corresponding properties of temp
temp.Left = node.Left;
temp.Left.Parent = temp;
temp.Color = node.Color;
}
//if the initial color of temp is black then red-black tree needs to be fixed
//the new tree must save the properties of red-black tree
if (tempInitialColor == NodeColor.Black)
{
this.DeleteFixup(fixupNode);
}
//decrement Count property of dictionary because one item is removed
--this.Count;
return(true);
}
/// <summary>
/// Fixes the Red-Black tree after insertion
/// </summary>
/// <param name="node"> Node. </param>
private void InsertFixup(NodeRB <TKey, TValue> node)
{
NodeRB <TKey, TValue> temp;
//starting Red-Black fixing process
while (node != this.root && node.Parent.Color == NodeColor.Red)
{
//if node's parent is a left child
if (node.Parent == node.Parent.Parent.Left)
{
//temp becomes the uncle of node
temp = node.Parent.Parent.Right;
//if the color of node's uncle is red
if (temp.Color == NodeColor.Red)
{
//the color of node's parent and node's uncle becomes black
node.Parent.Color = temp.Color = NodeColor.Black;
//the color of node's grandparent becomes red
node.Parent.Parent.Color = NodeColor.Red;
//node becomes the grandparent of node
node = node.Parent.Parent;
}
//else if the color of node's uncle is not red and node is a right child
else
{
if (node == node.Parent.Right)
{
//node becomes its parent
node = node.Parent;
//left rotate starting with node
this.LeftRotate(node);
}
//otherwise node's parent color becomes black,grandparent's color becomes red
//and rotate to the right starting with node's grandparent
node.Parent.Color = NodeColor.Black;
node.Parent.Parent.Color = NodeColor.Red;
this.RightRotate(node.Parent.Parent);
}
}
//otherwise if node's parent is a right child
else
{
//temp becomes the uncle of node
temp = node.Parent.Parent.Left;
//if the color of node's uncle is red
if (temp.Color == NodeColor.Red)
{
//the color of node's parent and uncle becomes black
node.Parent.Color = temp.Color = NodeColor.Black;
//the color of node's grandparent becomes red
node.Parent.Parent.Color = NodeColor.Red;
//node becomes the grandparent of node
node = node.Parent.Parent;
}
//else if the color of node's uncle is not red and node is a left child
else
{
if (node == node.Parent.Left)
{
//node becomes its parent
node = node.Parent;
//rotate the subtree starting with node to the right
this.RightRotate(node);
}
//otherwise
//the color of node's parent becomes black,the color of grandparent becomes red
node.Parent.Color = NodeColor.Black;
node.Parent.Parent.Color = NodeColor.Red;
//rotate the subtree starting with node's grandparent to the left
this.LeftRotate(node.Parent.Parent);
}
}
}
//set the color of the root as black
//because the color of the root of Red-Black tree must be black.
this.root.Color = NodeColor.Black;
}
/// <summary>
/// Inserts new node to the tree with the given key and value,if there is no
/// other element with that key
/// </summary>
/// <param name="key"> Key. </param>
/// <param name="value"> Value. </param>
private void Insert(TKey key, TValue value)
{
NodeRB <TKey, TValue> newNode = new NodeRB <TKey, TValue>(key, value, NodeColor.Red, null, nilNode, nilNode);
NodeRB <TKey, TValue> temp = this.root, newNodeParent = nilNode;
int comparison;
//First of all we have to find the parent of newNode
while (temp != nilNode)
{
//storing the parent
//we need to do this because in the last iteration node will become nillNode
newNodeParent = temp;
comparison = key.CompareTo(temp.Key);
//if the key is less than the key go to the left subtree
if (comparison == -1)
{
temp = temp.Left;
}
//else if the key is greater than the key go to the right subtree
else if (comparison == 1)
{
temp = temp.Right;
}
//otherwise if keys are equal
//keys equality means that element with that key already exists in the dictionary
//hence throw an exception
else
{
throw new Exception("Element with that key already exists in the dictionary");
}
}
//set the parent of newNode
newNode.Parent = newNodeParent;
//if newNode doesn't have parents then it becomes the root of the tree
if (newNode.Parent == nilNode)
{
this.root = newNode;
}
//else if the key is less then becomes the left child
else if (newNode.Key.CompareTo(newNodeParent.Key) < 0)
{
newNode.Parent.Left = newNode;
}
//otherwise newNode becomes its parent right child
else
{
newNode.Parent.Right = newNode;
}
newNode.Color = NodeColor.Red;
//incrementing the Count property of dictionary because new item is added
++this.Count;
//fix tree after insertion
this.InsertFixup(newNode);
}
/// <summary>
/// Creates new instance of dictionary.
/// </summary>
public DictionaryRB()
{
this.root = nilNode;
this.Count = 0;
}
/// <summary>
/// Clears the dictionary.
/// </summary>
public void Clear()
{
this.root = null;
this.Count = 0;
}