CS171, Homework 8

Preparation

To do this project, you must obtain a copy of the prepared files with these commands:

mkdir ~/cs171/hw8 cp /home/cs171000/Handouts/hw8/*.java ~/cs171/hw8 cp /home/cs171000/Handouts/hw8/*.class ~/cs171/hw8

Overview

In class, we discussed (and presented) algorithm to implement a Binary Search Tree to store information of the format:

public class Node { double value; // value is used to find nodes in the BST Node left; Node right; }

In this homework, you will implement a Binary Search Tree to store information of the format:

public class hw8Node { public String key; // key is used to find nodes in the BST public Integer value; public hw8Node left; public hw8Node right; }

This homework consists of 4 parts:

Part 1:
Part 2:

Part 3:

Write the put(k,v) method to insert or update the BST:

Part 4:

Important notices

Notices:

The Node object used by this homework assignment is defined in the class:
A Node object is therefore defined as follows:
So when you write the methods, you need to replace every Node variable definition with a hw8Node definition
The Java program file that you will use to write your program for this homework is called:
You must write the methods discussed above in this file.
Write one method at a time, and test the method using the provided test program before going to the next part.

When you write a method for the homework, do not re-invent the wheel !!!

Meaning: do not invent the algorithm for findNode(), put() and remove()

All you need to do to complete this project is:

Copy and paste the code of the desired method from the BST.java program (discussed in class) into the hw8BST.java program file.
Change the program code to use the variable key in the comparision operations (because the key filed is used to search the BST) !
(Note that the variable key is a String variable; you should know by now how to compare Strings !!!)

Part 1

Part 1:

Write the findNode(k) method of the a node with the key equal to k

findNode(k) must return the node if the key k was found
Otherwise, findNode(k) must return null (for "not found").
The variable myParent will point to the parent node

How to test part 1:

javac Part1.java java Part1

Correct output for part 1:

(z,40) (x,5) (u,45) (p,10) (m,50) (k,70) (d,30) (c,80) (a,7) ================================ p = (a,7), myParent of p = (d,30) p = (c,80), myParent of p = (a,7) p = (x,5), myParent of p = (p,10) p = (z,40), myParent of p = (x,5) p = (m,50), myParent of p = (m,50) p = (d,30), myParent of p = (m,50) p = (u,45), myParent of p = (x,5) p = (k,70), myParent of p = (d,30) p = (p,10), myParent of p = (m,50) p = null, myParent of p = (k,70) p = null, myParent of p = (u,45)

Part 2

Part 2:

Write the get(k) method to find the value that is associated with the key k (returns null if key was not found)

get(k) must return the Integer value that corresponds to the key k if it was found in the BST
Otherwise, get(k) must return null (for "not found").

Hint: use findNode()

How to test part 2:

javac Part2.java java Part2

Correct output for part 2:

(z,40) (x,5) (u,45) (p,10) (m,50) (k,70) (d,30) (c,80) (a,7) ================================ key = a, value of key = 7 key = c, value of key = 80 key = x, value of key = 5 key = z, value of key = 40 key = m, value of key = 50 key = d, value of key = 30 key = u, value of key = 45 key = k, value of key = 70 key = p, value of key = 10 key = e, value of key = null key = v, value of key = null

Part 3

Part 3:

Write the put(k,v) method to insert or update the BST:

Note:

You need to change the program code just a little bit:

How to test part 3:

javac Part3.java java Part3

Correct output for part 3:

(m,50) ================================ (m,50) (d,30) ================================ (m,50) (k,70) (d,30) ================================ (z,40) (x,5) (u,45) (p,10) (m,50) (k,70) (d,30) (c,80) (a,7) ================================ Updating (m,999) and (a,888): (z,40) (x,5) (u,45) (p,10) (m,999) (k,70) (d,30) (c,80) (a,888) ================================

Part 4

Part 4:

Write the remove(k) method delete the node containing the key k from the BST.

Note:

You need to change the program code just a little bit:

In case 3 of the remove() algorithm, when remove() copies the successor node to the node p, it must:

How to test part 4:

javac Part4.java java Part4

Correct output for part 4:

(z,90) (x,80) (v,75) (s,70) (m,50) (k,45) (i,40) (h,39) (g,38) (f,30) (e,10) (c,7) (a,5) ================================ *** remove c *** (z,90) (x,80) (v,75) (s,70) (m,50) (k,45) (i,40) (h,39) (g,38) (f,30) (e,10) (a,5) ================================ *** remove e *** (z,90) (x,80) (v,75) (s,70) (m,50) (k,45) (i,40) (h,39) (g,38) (f,30) (a,5) ================================ *** remove s *** (z,90) (x,80) (v,75) (m,50) (k,45) (i,40) (h,39) (g,38) (f,30) (a,5) ================================ *** remove f *** (z,90) (x,80) (v,75) (m,50) (k,45) (i,40) (h,39) (g,38) (a,5) ================================ *** remove all, except i *** (i,40) ================================ *** remove i *** ================================

Turnin
- Use the following command (from inside your cs171/hw8 project directory) to turn in your program: