Description
In this lab, you are going to practice traversing a tree using recursion with a little of backtracking. Recall that a path begins at the root and goes from node to node along the edges
that join them. Suppose we name a left edge ’0’ and the right edge ’1’ as shown in Figure
below:
a
b
c
d
e
g f
0
0 0 1 1
1
In doing so, we can represent a path by a string of 0s and 1s. For example, the path to the
node containing ’g’ is “01”, the path to the node containing ’b’ is “10”, the path to the
node containing ’c’ is “” (empty string), and so on.
What to Do?
For this lab, you are going to implement two methods marked TO DO in ShowPath.java.
In ShowPath.java, a tree of random unique characters is constructed using the method
generateTree(). This tree consists of characters from ’a’ to ’z’ and from ’A’ to ’Z’. The
method generateTree() will return the root node (of type BinaryNodeInterface
of the tree of characters. Note that a series of BinaryNode can be viewed as a tree. So,
for this lab, you are going to work with a series of BinaryNodes instead of a tree. The two
methods that you have to implement are as follows:
1. String getAllPaths(final BinaryNodeInterface
simply returns a string representing all paths to every nodes of the tree root at root.
The returned string must be in the following format:
r
d 0
U 00
t 000
CS 0445 — Data Structures Page 1
Lab 10: Tree
I 0000
Y 00000
P 00001
M 0001
T 00010
:
:
b 110
h 1100
Q 1101
y 111
O 1110
s 1111
Note that the format for each line must be a character, follows by a single space,
follows by the string representing the path from the root note to the node containing
the character, and follows by the newline character (’\n’). If your format is incorrect,
the tester may report incorrect test result. The above example is done according to
Preorder Traversal. However, you can use any type of traversal. Note that YOU
MUST use a type of traversal. You are NOT ALLOWED to use the method
getPathTo().
2. String getPathTo(final BinaryNodeInterface
method returns a string representing a path from the root to the node containing the
character c.
Test Class
Methods to test your implementations are included in ShowPath.java. This will test your
implementation of methods getAllPaths() and getPathTo() and show your total points
(out of 10). If you do not get the full 10 points, you should keep trying to fix your code until
you get 10 points. Note that these test methods are not perfect. It cannot tell you why
your program is incorrect. You may have to look at the source code of checkGetAllPaths()
and checkGetPathTo() and see why it says FAIL and trace your code.
Due Date and Submission
For the due date, please check the lab in the CourseWeb. Submit your ShowPath.java to
the CourseWeb under this lab by the due date. No late submission will be accepted.
CS 0445 — Data Structures Page 2
