ADV DESIGN & ANALY OF ALGOR

Learning Goal: I’m working on a computer science discussion question and need an explanation and answer to help me learn.

In class we have seen implementations of several methods for a scapegoat tree data structure in Java. For this
assignment, you will implement four methods as outlined below in Java.
0.Use the code from class / Canvas as a starting point or start yourself from scratch to have a class
ScapegoatTree with generic key-value nodes.
1.Write postOrder and preOrder walk methods which take no input and return a list of tree nodes in the
respective order.
2.Override the toString method of the Scapegoat tree class. Use the appropriate form of in-order, pre-order,
or post-order walk to form a string of all current keys which recursively contains parent(children) pairs. Adapt
your method from the methods you implemented in Exercise 1. As an example, if a parent has a left and a right
child who in turn have left and right grandchildren, your return string would look like
parent.key(left.key(lleftgrand.key(…), lrightgrand.key(…)), right.key(…)).
If exactly one of the children is null, print a space in its place. If both children are null, the parent is actually
a leaf and no recursion should be executed and no parentheses should be printed.
For example, the tree in Figure 1 in the Galperin/Rivest 1993 paper should yield the string
2(1,6(5(4(3, ), ),15(12(9(7,11(10, )),13( ,14)),16( ,17( ,18))))).
Hint: It is probably easiest to create the return string while traversing (instead of after traversing) similar to
collecting the nodes in the inOrder method shown in class. That means you would need a mutable string object.
Since Java the String type is immutable, use one of the two mutable Java string types.
3.Write a public method successor which finds the successor of a given key by finding the successor node and
returning the key of that node. If a successor does not exist, return the original key. Recall that the successor of
a node n is either the minimum node in the right subtree of n or the first parent of node n for which n is located
in the left parent sub-tree.
4.Write a public method predecessor which finds the predecessor of a given key by finding the predecessor
node and returning the key of that node. If a predecessor does not exist, return the original key. Recall that the
predecessor of a node n is either the maximum node in the left subtree of n or the first parent of node n for
which n is located in the right parent sub-tree.
5.Test and debug your methods. Provide test runs in form of a main (driver) file in which you create appropriate
variables, fill the tree with data from the provided JSON file, and run some cases to show your methods work.
Do not forget to upload Main.java and ScapegoatTree.java, as well as a screen shot of test runs. Recall
that the Gson library needs to be included by going to File→Project Structure→Libraries→+→from Maven,
and then search for com.google.gson.Gson.
Each of the problems 1 – 5 will be graded according to the following rubric for a total of 20 points.
SCORE 4 3 2 1 0
SKILL LEVEL Response gives
evidence of a
complete
understanding of
the problem; is
fully developed; is
clearly
communicated.
Response gives the
evidence of a clear
understanding of
the problem but
contains minor
errors or is not
fully
communicated.
Response gives
evidence of a
reasonable
approach but
indicates gaps in
conceptual
understanding.
Explanations are
incomplete, vague,
or muddled.
Response gives
some evidence of
problem
understanding
but contains
major math or
reasoning errors.
No response or
response is
completely
incorrect or
irrelevant.