$/**$

$*$ Find all elements within a certain distance from the given data.

$*$ "Distance" means the number of edges between two nodes in the tree.

$*$

$*$ To do this, first find the data in the tree. Keep track of the distance

$*$ of the current node on the path to the data $($you can use the return

$*$ value of a helper method to denote the current distance to the target

$*$ data $-$ but note that you must find the data first before you can

$*$ calculate this information$).$ After you have found the data, you should

$*$ know the distance of each node on the path to the data. With that

$*$ information, you can determine how much farther away you can traverse

$*$ from the main path while remaining within distance of the target data.

$*$

$*$ Use a HashSet as the Set you return. Keep in mind that since it is a

$*$ Set, you do not have to worry about any specific order in the Set.

$*$

$*$ This must be implemented recursively.

$*$

$*$ Ex:

$*$ Given the following AVL composed of Integers

$*50$

$*/\backslash$

$*2575$

$*/\backslash /\backslash$

$*13377080$

$*/\backslash \backslash \backslash$

$*12154085$

$*/$

$*10$

$*$ elementsWithinDistance$(37,3)$ should return the set $\{12,13,15,25,$

$*37,40,50,75\}$

$*$ elementsWithinDistance$(85,2)$ should return the set $\{75,80,85\}$

$*$ elementsWithinDistance$(13,1)$ should return the set $\{12,13,15,25\}$

$*$

$*$ @param data the data to begin calculating distance from

$*$ @param distance the maximum distance allowed

$*$ @return the set of all data within a certain distance from the given data

$*$ @throws java.lang.IllegalArgumentException if data is null

$*$ @throws java.util.NoSuchElementException is the data is not in the tree

$*$ @throws java.lang.IllegalArgumentException if distance is negative

$*/$