private void RotateRight(Node b)
{
Node a = b.left;
b.left = a.right;
if (a.right != null)
{
a.right.parent = b;
}
if (a != null)
{
a.parent = b.parent;
}
if (b.parent == null)
{
root = a;
}
if (b == b.parent.right)
{
b.parent.right = a;
}
else
{
b.parent.left = a;
}
a.right = b;
if (b != null)
{
b.parent = a;
}
}
private void RotateLeft(Node a)
{
Node b = a.right;
a.right = b.left;
if (b.left != null)
{
b.left.parent = a;
}
if (b != null)
{
b.parent = a.parent;
}
if (a.parent == null)
{
root = b;
}
if (a == a.parent.left)
{
a.parent.left = b;
}
else
{
a.parent.right = b;
}
b.left = a;
if (a != null)
{
a.parent = b;
}
}
public RedBlackTree()
{
this.root = null;
}
private Node Successor(Node a)
{
if (a.left != null)
{
while (a.left.left != null)
{
a = a.left;
}
if (a.left.right != null)
{
a = a.left.right;
}
return a;
}
else
{
Node b = a.parent;
while (b != null && a == b.right)
{
a = b;
b = b.parent;
}
return b;
}
}
private void RemoveFix(Node a)
{
while (a != null && a != root && a.color == Color.Black)
{
if (a == a.parent.left)
{
Node b = a.parent.right;
if (b.color == Color.Red)
{
b.color = Color.Black; // case 1
a.parent.color = Color.Red;
RotateLeft(a.parent);
b = a.parent.right;
}
if (b.left.color == Color.Black && b.right.color == Color.Black)
{
b.color = Color.Red; // case 2
a = a.parent;
}
else if (b.right.color == Color.Black)
{
b.left.color = Color.Black; // case 3
b.color = Color.Red;
RotateRight(b);
b = a.parent.right;
}
b.color = a.parent.color; //case 4
a.parent.color = Color.Black;
b.right.color = Color.Black;
RotateLeft(a.parent);
a = root;
}
else //mirror code
{
Node b = a.parent.left;
if (b.color == Color.Red)
{
b.color = Color.Black;
a.parent.color = Color.Red;
RotateRight(a.parent);
b = a.parent.left;
}
if (b.right.color == Color.Black && b.left.color == Color.Black)
{
b.color = Color.Black;
a = a.parent;
}
else if (b.left.color == Color.Black)
{
b.right.color = Color.Black;
b.color = Color.Red;
RotateLeft(b);
b = a.parent.left;
}
b.color = a.parent.color;
a.parent.color = Color.Black;
b.left.color = Color.Black;
RotateRight(a.parent);
a = root;
}
}
if (a != null)
{
a.color = Color.Black;
}
}
public void Remove(int data)
{
Node a = Find(data);
Node b = null;
Node c = null;
if (a == null)
{
Console.WriteLine("Nothing to delete");
return;
}
if (a.left == null || a.right == null)
{
c = a;
}
else
{
c = Successor(a);
}
if (c.left != null)
{
b = c.left;
}
else
{
b = c.right;
}
if (b != null)
{
b.parent = c;
}
if (c.parent == null)
{
root = b;
}
else if (c == c.parent.left)
{
c.parent.left = b;
}
else
{
c.parent.left = b;
}
if (c != a)
{
a.data = c.data;
}
if (c.color == Color.Black)
{
RemoveFix(b);
}
}
private void AddFix(Node a)
{
while (a != root && a.parent.color == Color.Red)
{
if (a.parent == a.parent.parent.left)
{
Node b = a.parent.parent.right;
if (b != null && b.color == Color.Red) //Case 1: uncle is red
{
a.parent.color = Color.Black;
b.color = Color.Black;
a.parent.parent.color = Color.Red;
a = a.parent.parent;
}
else //Case 2: uncle is black
{
if (a == a.parent.right)
{
a = a.parent;
RotateLeft(a);
}
//Case 3: recolor and rotate
a.parent.color = Color.Black;
a.parent.parent.color = Color.Red;
RotateRight(a.parent.parent);
}
}
else //mirror image of code above
{
Node b = null;
b = a.parent.parent.left;
if (b != null && b.color == Color.Black)//Case 1
{
a.parent.color = Color.Red;
b.color = Color.Red;
a.parent.parent.color = Color.Black;
a = a.parent.parent;
}
else
{
if (a == a.parent.left)
{
a = a.parent;
RotateRight(a);
}
a.parent.color = Color.Black;
a.parent.parent.color = Color.Red;
RotateLeft(a.parent.parent);
}
}
root.color = Color.Black;
}
}
public void Add(int data)
{
Node newNode = new Node(data);
if (root == null)
{
root = newNode;
root.color = Color.Black;
return;
}
Node a = null;
Node b = root;
while (b != null)
{
a = b;
if (newNode.data < b.data)
{
b = b.left;
}
else
{
b = b.right;
}
}
newNode.parent = a;
if (a == null)
{
root = newNode;
}
else if (newNode.data < a.data)
{
a.left = newNode;
}
else
{
a.right = newNode;
}
newNode.left = null;
newNode.right = null;
newNode.color = Color.Red;
AddFix(newNode);
}