/// <summary>
/// Propagates resizing of the nodes upwards. Additionally, performs
/// any splitting of nodes along the way if a node needed to split.
/// Returns whether the root node was split.
/// </summary>
/// <param name="adjustPath">Path along which the nodes need be adjusted</param>
/// <param name="node">Node above which needs to be adjusted</param>
/// <param name="splitNode">Node that needs to be inserted.</param>
/// <returns>True if the root node was split</returns>
private bool adjustTree(List <NodeRecord <T> > adjustPath,
NodeRecord <T> node, ref NodeRecord <T> splitNode)
{
// AT1.
NodeRecord <T> N = node;
NodeRecord <T> NN = splitNode;
while (true)
{
// AT2.
if (N == root)
{
return(NN != null);
}
// AT3.
N.ResizeBBox();
// AT4.
// Try to add the extra node to this parent node.
// If the parent has no more room, split the parent,
// and propagate the split node upwards to continue
// looking for an insertion point.
int level = adjustPath.IndexOf(N);
NodeRecord <T> P = adjustPath[level - 1];
if (NN != null)
{
if (!P.TryInsert(NN))
{
NodeRecord <T> PP = P.Split(NN);
NN = PP;
}
else
{
NN = null;
}
}
N = P;
}
}
/// <summary>
/// Performs the insertion algorithm.
/// </summary>
/// <param name="item">Item to insert</param>
public void Insert(LeafRecord <T> item)
{
List <NodeRecord <T> > leafPath = new List <NodeRecord <T> >();
// I1.
// Track the nodes traversed to get to the point that we
// want to add the node. This list of nodes will be used
// to propagate changes up the tree.
NodeRecord <T> insertNode = chooseLeaf(item, leafPath);
NodeRecord <T> splitNode = null;
// I2.
// Attempts to insert the item in the given node.
// If it fails, we split the node. Store the new
// node in splitNode, so it can be propagated up
// later.
if (!insertNode.TryInsert(item))
{
// Split.
splitNode = insertNode.Split(item);
}
// I3.
// Propagate resizing up the tree. Propagate split node
// if necessary.
if (adjustTree(leafPath, insertNode, ref splitNode))
{
// I4.
// Create a new root if the root was split. This new root is not a leaf.
NodeRecord <T> newRoot = new NodeRecord <T>()
{
Node = new RTreeNode <T>(Leaf: false)
};
newRoot.TryInsert(root);
newRoot.TryInsert(splitNode);
root = newRoot;
}
}