private RbNode Insert(int key, int data, RbNode root)
{
RbNode parent = null;
RbNode node = null;
node = SearchAuxiliary(key, root, ref parent);
if (node != null)
{
node.Data++;
return(root);
}
node = CreateNode(key, data);
node.Parent = parent;
if (parent != null)
{
if (parent.Key > key)
{
parent.Left = node;
}
else
{
parent.Right = node;
}
}
else
{
root = node;
}
return(InsertRebalance(node, root));
}
/// <summary>
/// left rotate: ==>
/// node right
/// /\ /\
/// a right node y
/// /\ /\
/// b y a b
/// </summary>
/// <param name="node"></param>
/// <param name="root"></param>
/// <returns></returns>
private RbNode RotateLeft(RbNode node, RbNode root)
{
RbNode right = node.Right;
if (node.Right == right.Left)
{
right.Left.Parent = node;
}
right.Left = node;
if (right.Parent == node.Parent)
{
if (node == node.Parent.Right)
{
node.Parent.Right = right;
}
else
{
node.Parent.Left = right;
}
}
else
{
root = right;
}
node.Parent = right;
return(root);
}
private RbNode SearchAuxiliary(int key, RbNode root, ref RbNode save)
{
RbNode node = root;
RbNode parent = null;
int ret;
while (node != null)
{
parent = node;
ret = node.Key - key;
if (ret > 0)
{
node = node.Left;
}
else if (ret < 0)
{
node = node.Right;
}
else
{
return(node);
}
}
if (parent != null)
{
save = parent;
}
return(null);
}
/// <summary>
/// right rotate ==> left
/// node /\
/// /\ a node
/// left y /\
/// /\ b y
/// a b
/// </summary>
/// <param name="node"></param>
/// <param name="root"></param>
/// <returns></returns>
private RbNode RotateRight(RbNode node, RbNode root)
{
RbNode left = node.Left;
if (node.Left == left.Right)
{
left.Right.Parent = node;
}
left.Right = node;
if (left.Parent == node.Parent)
{
if (node == node.Parent.Right)
{
node.Parent.Right = left;
}
else
{
node.Parent.Left = left;
}
}
else
{
root = left;
}
node.Parent = left;
return(root);
}
private RbNode CreateNode(int key, int data)
{
RbNode node = new RbNode
{
Key = key,
Data = data,
Color = RbColor.Red
};
return(node);
}
private RbNode Search(int key, RbNode root)
{
RbNode parent = root;
return(SearchAuxiliary(key, root, ref parent));
}
/// <summary>
/// The 3 cases of red-black tree insertion
/// z stands for current node, p[z] is parent, p[p[z]] is grandparent, y is uncle
/// </summary>
/// <param name="node"></param>
/// <param name="root"></param>
/// <returns></returns>
private RbNode InsertRebalance(RbNode node, RbNode root)
{
RbNode parent, gparent, uncle, temp;
while ((parent = node.Parent) != null && parent.Color == RbColor.Red)
{
gparent = parent.Parent;
if (parent == gparent.Left)
{
uncle = gparent.Right;
if (uncle != null && uncle.Color == RbColor.Red)
{
uncle.Color = RbColor.Black;
parent.Color = RbColor.Black;
gparent.Color = RbColor.Red;
node = gparent;
}
else
{
if (parent.Right == node)
{
root = RotateLeft(parent, root);
temp = parent;
parent = node;
node = temp;
}
parent.Color = RbColor.Black;
gparent.Color = RbColor.Red;
root = RotateRight(gparent, root);
}
}
else
{
uncle = gparent.Left;
if (uncle != null && uncle.Color == RbColor.Red)
{
uncle.Color = RbColor.Black;
parent.Color = RbColor.Black;
gparent.Color = RbColor.Red;
node = gparent;
}
else
{
if (parent.Left == node)
{
root = RotateRight(parent, root);
temp = parent;
parent = node;
node = temp;
}
parent.Color = RbColor.Black;
gparent.Color = RbColor.Red;
root = RotateLeft(gparent, root);
}
}
}
root.Color = RbColor.Black;
return(root);
}
