public void Delete(RBTreeNode node, int value)
{
// Traverse until we find nodeToDelete
RBTreeNode nodeToDelete = null;
while (node != null)
{
if (node.GetData() == value)
{
nodeToDelete = node;
break;
}
node = (value < node.GetData()) ? node.Left() : node.Right();
}
if (nodeToDelete == null)
{
throw new Exception("Cannot find node to delete with " +
$"value {value} in Red Black Tree");
}
RBTreeNode x, y;
// Save the color of nodeToDelete
bool originallyRed = nodeToDelete.IsRed();
// If nodeToDelete only has left children, replace with its left subtree
if (nodeToDelete.Left() == null || nodeToDelete.Left().IsEmpty())
{
x = nodeToDelete.Right();
if (x == null)
{
x = Leaf;
}
Transplant(nodeToDelete, x);
// If nodeToDelete only has right children, replace with its right subtree
}
else if (nodeToDelete.Right() == null || nodeToDelete.Right().IsEmpty())
{
x = nodeToDelete.Left();
if (x == null)
{
x = Leaf;
}
Transplant(nodeToDelete, x);
}
else // nodeToDelete either has two children or is a leaf
// y = smallest node whose value is greater than that of nodeToDelete
// will replace nodeToDelete
{
y = Minimum(nodeToDelete.Right());
originallyRed = y.IsRed();
// x = subtree root with values greater than y
x = y.Right();
if (x == null)
{
x = Leaf;
}
// if y is a child of nodeToDelete, x is already stored in the right place
if (y.Parent() == nodeToDelete)
{
x.SetParent(y);
}
else // else replace y with its right subtree and update attributes
{
Transplant(y, y.Right());
y.SetRight(nodeToDelete.Right());
y.Right().SetParent(y);
}
// replace nodeToDelete with y and update attributes
Transplant(nodeToDelete, y);
y.SetLeft(nodeToDelete.Left());
y.Left().SetParent(y);
// y will replace nodeToDelete's location in tree, update its color
if (originallyRed)
{
y.SetRed();
}
else
{
y.SetBlack();
}
}
if (!(originallyRed))
{
RebalancePostDeletion(x);
}
}
