// in order traversal, returns a string containing all elements
// implemented making use of the parent nodes to test their functionality
public string ParentTraverse()
{
BinarySearchTreeNode <T> current = root;
BinarySearchTreeNode <T> previous;
string output = "";
if (current == null)
{
return(output);
}
// loops until returning to root from the right or from left if there is no right branch
do
{
// moves to furthest left child of current and adds its value to output, sets previous to current
while (current.left != null)
{
current = current.left;
}
previous = current;
output += current.value + " ";
// traverses parent nodes until reaching a node with an unvisited right node or reaching the root
while ((current.right == null || current.right == previous) && current.parent != null)
{
// sets previous to current then sets current to parent and adds value to output if previous was not on right side
previous = current;
current = current.parent;
if (current.right != previous)
{
output += current.value + " ";
}
}
// if there is an unvisited branch to the right, moves current to right
if (current.right != previous && current.right != null)
{
current = current.right;
}
} while (current.parent != null);
return(output);
}
//private insert, takes a node and item and attempts to insert at that node
// if node is not empty recurses on left/right node if item is smaller/larger than item at current position
private BinarySearchTreeNode <T> Insert(BinarySearchTreeNode <T> child, T item)
{
if (child == null)
{
child = new BinarySearchTreeNode <T>();
child.value = item;
}
// insertion logic, if the value (v )is < root, insert to the root.left
// otherwise it's >=, so insert to the right
// connects node to parent after
else if (item.CompareTo(child.value) < 0)
{
child.left = Insert(child.left, item);
child.left.parent = child;
}
else
{
child.right = Insert(child.right, item);
child.right.parent = child;
}
return(child);
}
