private void RightRotate(NodeRBT Y)
{
NodeRBT X = Y.left;
Y.left = X.right;
if (X.right != null)
{
X.right.parent = Y;
}
if (X != null)
{
X.parent = Y.parent;
}
if (Y.parent == null)
{
root = X;
}
if (Y == Y.parent.right)
{
Y.parent.right = X;
}
if (Y == Y.parent.left)
{
Y.parent.left = X;
}
X.right = Y;
if (Y != null)
{
Y.parent = X;
}
}
private void LeftRotate(NodeRBT X)
{
NodeRBT Y = X.right;
X.right = Y.left;
if (Y.left != null)
{
Y.left.parent = X;
}
if (Y != null)
{
Y.parent = X.parent;
}
if (X.parent == null)
{
root = Y;
}
if (X == X.parent.left)
{
X.parent.left = Y;
}
else
{
X.parent.right = Y;
}
Y.left = X;
if (X != null)
{
X.parent = Y;
}
}
private void InsertFixUp(NodeRBT item)
{
//Checks Red-Black Tree properties
while (item != root && item.parent.color == 1)
{
/*We have a violation*/
if (item.parent == item.parent.parent.left)
{
NodeRBT Y = item.parent.parent.right;
if (Y != null && Y.color == 1)//Case 1: uncle is red
{
item.parent.color = 0;
Y.color = 0;
item.parent.parent.color = 1;
item = item.parent.parent;
}
else //Case 2: uncle is black
{
if (item == item.parent.right)
{
item = item.parent;
LeftRotate(item);
}
//Case 3: recolour & rotate
item.parent.color = 0;
item.parent.parent.color = 1;
RightRotate(item.parent.parent);
}
}
else
{
//mirror image of code above
NodeRBT X = null;
X = item.parent.parent.left;
if (X != null && X.color == 1)//Case 1
{
item.parent.color = 0;
X.color = 1;
item.parent.parent.color = 0;
item = item.parent.parent;
}
else //Case 2
{
if (item == item.parent.left)
{
item = item.parent;
RightRotate(item);
}
//Case 3: recolour & rotate
item.parent.color = 1;
item.parent.parent.color = 0;
LeftRotate(item.parent.parent);
}
}
root.color = 1;//re-colour the root black as necessary
}
}
public void Delete(int key)
{
NodeRBT item = Find(key);
NodeRBT X = null;
NodeRBT Y = null;
if (item == null)
{
Console.WriteLine("Nothing to delete!");
return;
}
if (item.left == null || item.right == null)
{
Y = item;
}
else
{
Y = TreeSuccessor(item);
}
if (Y.left != null)
{
X = Y.left;
}
else
{
X = Y.right;
}
if (X != null)
{
X.parent = Y;
}
if (Y.parent == null)
{
root = X;
}
else if (Y == Y.parent.left)
{
Y.parent.left = X;
}
else
{
Y.parent.left = X;
}
if (Y != item)
{
item.data = Y.data;
}
if (Y.color == 1)
{
DeleteFixUp(X);
}
}
private NodeRBT Minimum(NodeRBT X)
{
while (X.left.left != null)
{
X = X.left;
}
if (X.left.right != null)
{
X = X.left.right;
}
return(X);
}
private NodeRBT TreeSuccessor(NodeRBT X)
{
if (X.left != null)
{
return(Minimum(X));
}
else
{
NodeRBT Y = X.parent;
while (Y != null && X == Y.right)
{
X = Y;
Y = Y.parent;
}
return(Y);
}
}
public void Insert(int item)
{
NodeRBT newItem = new NodeRBT(item);
if (root == null)
{
root = newItem;
root.color = 1;
return;
}
NodeRBT Y = null;
NodeRBT X = root;
while (X != null)
{
Y = X;
if (newItem.data < X.data)
{
X = X.left;
}
else
{
X = X.right;
}
}
newItem.parent = Y;
if (Y == null)
{
root = newItem;
}
else if (newItem.data < Y.data)
{
Y.left = newItem;
}
else
{
Y.right = newItem;
}
newItem.left = null;
newItem.right = null;
newItem.color = 0;
InsertFixUp(newItem);
}
public NodeRBT Find(int key)
{
bool isFound = false;
NodeRBT temp = root;
NodeRBT item = null;
while (!isFound)
{
if (temp == null)
{
break;
}
if (key < temp.data)
{
temp = temp.left;
}
if (key > temp.data)
{
temp = temp.right;
}
if (key == temp.data)
{
isFound = true;
item = temp;
}
}
if (isFound)
{
Console.WriteLine("{0} was found", key);
return(temp);
}
else
{
Console.WriteLine("{0} not found", key);
return(null);
}
}
private void DeleteFixUp(NodeRBT X)
{
while (X != null && X != root && X.color == 1)
{
if (X == X.parent.left)
{
NodeRBT W = X.parent.right;
if (W.color == 0)
{
W.color = 1;
X.parent.color = 0;
LeftRotate(X.parent);
W = X.parent.right;
}
if (W.left.color == 1 && W.right.color == 1)
{
W.color = 0;
X = X.parent;
}
else if (W.right.color == 1)
{
W.left.color = 1;
W.color = 0;
RightRotate(W);
W = X.parent.right;
}
W.color = X.parent.color;
X.parent.color = 1;
W.right.color = 1;
LeftRotate(X.parent);
X = root;
}
else
{
NodeRBT W = X.parent.left;
if (W.color == 0)
{
W.color = 1;
X.parent.color = 0;
RightRotate(X.parent);
W = X.parent.left;
}
if (W.right.color == 1 && W.left.color == 1)
{
W.color = 1;
X = X.parent;
}
else if (W.left.color == 1)
{
W.right.color = 1;
W.color = 0;
LeftRotate(W);
W = X.parent.left;
}
W.color = X.parent.color;
X.parent.color = 1;
W.left.color = 1;
RightRotate(X.parent);
X = root;
}
}
if (X != null)
{
X.color = 1;
}
}
public NodeRBT(int data)
{
this.data = data;
left = right = parent = null;
color = 0;
}