private void Delete(OrderedTreeNode z)
{
// A node to be deleted will be:
// 1. a leaf with no children
// 2. have one child
// 3. have two children
// If the deleted node is red, the red black properties still hold.
// If the deleted node is black, the tree needs rebalancing
OrderedTreeNode x = new OrderedTreeNode(); // work node to contain the replacement node
OrderedTreeNode y; // work node
// find the replacement node (the successor to x) - the node one with
// at *most* one child.
if(z.Left == sentinelNode || z.Right == sentinelNode)
y = z; // node has sentinel as a child
else {
// z has two children, find replacement node which will
// be the leftmost node greater than z
y = z.Right; // traverse right subtree
while(y.Left != sentinelNode) // to find next node in sequence
y = y.Left;
}
// at this point, y contains the replacement node. it's content will be copied
// to the valules in the node to be deleted
// x (y's only child) is the node that will be linked to y's old parent.
if(y.Left != sentinelNode)
x = y.Left;
else
x = y.Right;
// replace x's parent with y's parent and
// link x to proper subtree in parent
// this removes y from the chain
x.Parent = y.Parent;
if(y.Parent != null)
if(y == y.Parent.Left)
y.Parent.Left = x;
else
y.Parent.Right = x;
else
rbTree = x; // make x the root node
// copy the values from y (the replacement node) to the node being deleted.
// note: this effectively deletes the node.
if(y != z) {
z.Key = y.Key;
z.Data = y.Data;
}
if(y.Color == OrderedTreeNode.BLACK)
RestoreAfterDelete(x);
lastNodeFound = sentinelNode;
}
