public RBTNode FlipColors(RBTNode head)
{
//only flip if parent node is not red & both child nodes are red
if (!head.red && head.left.red && head.right.red)
{
//if parent is the root, which always has to be black, don't flip the color
if (head != root)
{
head.red = true;
}
head.left.red = false;
head.right.red = false;
}
return head;
}
public RBTNode Insert(RBTNode head, int value)
{
RBTNode node;
//if empty tree, create root/leaf node, which is always black
if (head == null)
{
node = new RBTNode(value, false);
//if root node hasn't been set, then assume empty tree and set it now
if (root == null) { root = node; }
return node;
}
else
{
//Standard Binary Search Tree Insert
if (value < head.data)
{
head.left = Insert(head.left, value);
} else if (value > head.data)
{
head.right = Insert(head.right, value);
} else
{
head.data = value;
}
}
//if we have a red node on the right, then rotate left to
//maintain the the left-leaning red property.
if (head.right.red && !head.left.red)
{
head = RotateLeft(head);
}
//case where we have 2 consecutive red nodes
if (head.left.red && head.left.left.red)
{
head = RotateRight(head);
}
//case where we have a node with 2 red links;
if (head.left.red && head.right.red)
{
head = FlipColors(head);
}
return head;
}
public RBTNode RotateRight(RBTNode head)
{
RBTNode tmp = head;
if (head.left.red)
{
tmp = head.left;
head.left = tmp.right;
tmp.right = head;
tmp.red = head.red;
if (head == root)
{
//rotated the root node out, update root node and remain black
root = tmp;
tmp.red = false;
}
head.red = true;
}
return tmp;
}
