// finds the TreeNode with the smallest key more than nextKey
public ListItemStats <KeyType, ValueType> FindNextItem(KeyType nextKey, bool strictlyGreater)
{
TreeNode <KeyType, ValueType> bestNode = null;
TreeNode <KeyType, ValueType> currentNode = this.rootNode;
while (currentNode != null)
{
// choose the child to move to
if (this.ChooseLeftChild(nextKey, currentNode, !strictlyGreater))
{
// keep track of the rightmost node found so far that is to the left of this one
bestNode = currentNode;
// move to the correct child
currentNode = currentNode.LeftChild;
}
else
{
// move to the correct child
currentNode = currentNode.RightChild;
}
}
ListItemStats <KeyType, ValueType> result = null;
if (bestNode != null)
{
result = bestNode.Stats;
}
return(result);
}
// finds the TreeNode with the largest key less than nextKey
private ListItemStats <KeyType, ValueType> FindPreviousItem(KeyType nextKey, bool strictlyLess, TreeNode <KeyType, ValueType> startingNode)
{
TreeNode <KeyType, ValueType> bestNode = null;
TreeNode <KeyType, ValueType> currentNode = startingNode;
while (currentNode != null)
{
// remember the last node we visited
this.latestNode = currentNode;
// choose the child to move to
if (this.ChooseLeftChild(nextKey, currentNode, strictlyLess))
{
// move to the correct child
currentNode = currentNode.LeftChild;
}
else
{
// keep track of the number of items before this one, including itself
//lowerCount += currentNode.GetNumLeftChildren() + 1;
// keep track of the rightmost node found so far that is to the left of this one
bestNode = currentNode;
// move to the correct child
currentNode = currentNode.RightChild;
}
}
ListItemStats <KeyType, ValueType> result = null;
if (bestNode != null)
{
result = bestNode.Stats;
}
return(result);
}
