CSE2/CSE5ALG– Algorithms and Data Structures – 2020

CSE2/CSE5ALG– Algorithms and Data Structures – 2020
Assignment – Part 1
Assessment: This part 1 of the assignment is worth 10% of the final mark for this subject.
Due Date: 9 April 2020, Thursday, at 10:00 AM
Delays caused by computer downtime cannot be accepted as a valid reason for a late submission
without penalty. Students must plan their work to allow for both scheduled and
unscheduled downtime. Late submission policy does NOT apply to this assignment.
Copying, Plagiarism: Plagiarism is the submission of somebody else’s work in a manner that
gives the impression that the work is your own. The Department of CS & IT treats academic
misconduct seriously. When it is detected, penalties are strictly imposed.
Submission Details: Submit all the Java files that are required for the tasks described in this
handout. The code has to run under Unix on the latcs8 machine. You submit your files from your
latcs8 account. Make sure you are in the same directory as the files you are submitting. Submit
each file separately using the submit command. For example, if the file is named
LexiconTester.java, use the following command for submission:
submit ALG LexiconTester.java
After submitting the files, you can run the following command that lists the files submitted
from your account:
verify
You can submit the same filename as many times as you like before the assignment deadline;
the previously submitted copy will be replaced by the latest one. If you encounter any problem
regarding submission, please email the lecturer for assistance.
Testing Platform: While you are free to develop the code on any operating system, your
solution must be compilable and executable using javac and java commands on latcs8.
Return of Assignment: The tutor is to mark your assignment with a marking sheet in
a face-to-face pattern during the online lab classes in the next teaching week after the
due date. You will be notified with your mark immediately after marking. If you
have any doubt your mark, please raise it to the tutor before your lab class ends.
Any post-lab inquiry will NOT be accepted. If you miss your lab, please email the lecturer
for arrangement of marking.
Assignment Objectives
• To understand various data structures and searching and sorting techniques;
• To analyse these techniques in relation to a particular problem;
• To implement these techniques within a Java program.
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Problem Description
In many situations, we may need to find a word based on one or more letters in it. For example,
when making or completing a crossword you may want to find a word that has 4 letters, starts with
J and ends with A. In this assignment, the program you will write will create a lexicon of words
from various sources (that is, from various text files) and will allow the user to search for words
that fit particular patterns.
The operational definition of what is taken to be a word will be given later in this handout. For
each word, we also keep the following information:
• The frequency: How many times the word appears in the input files
• The list of neighbors: A neighbor of a word w is a word that is of the same length and differs
from w by only one letter
Note: The motivation for this requirement is to make the lexicon capable of supporting the
following game. Two words are given – let us called them “start word” and “end word”. The
aim is to transform the start word into the end word by changing one letter at a time, subject
to the condition that all the intermediate “words” are valid words. Obviously, this game is
equivalent to finding a path from the start word to the end word along the edges connecting
two neighbors.
Assignment Requirements
The assignment is divided into two parts. For part 1, you are required to write a simple version,
where execution efficiency is not taken into account. For part 2, you are required to write an
“optimized” version where efficiency, in addition to correctness, is the major concern.
With the exceptions of ArrayList, you are NOT permitted to use any of the classes in
the Java Collections Framework, e.g. TreeMap, HashMap, Arrays.
Task 1
For this task, you are to design and implement the program LexiconTester.java. This program
will
1. Read two text files, sample1.txt and sample2.txt, and construct a lexicon that contains
words from the two files;
2. Write the words from the lexicon to the text file sample3.txt.
Further information about the task is given below.
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Building the lexicon
The first text file to be read in is the file sample1.txt shown below:
Pride and Prejudice
by Jane Austen
Chapter 1
It is a truth universally acknowledged that a single man in possession of a
good fortune must be in want of a wife.
However little known the feelings or views of such a man may be on his first
entering a neighbourhood, this truth is so well fixed in the minds of the
surrounding families, that he is considered the rightful property of some one
or other of their daughters.
“My dear Mr. Bennet,” said his lady to him one day, “have you heard that
Netherfield Park is let at last?”
Mr. Bennet replied that he had not.
“But it is,” returned she; “for Mrs. Long has just been here, and she told
me all about it.”
Mr. Bennet made no answer.
“Do you not want to know who has taken it?” cried his wife impatiently.
“YOU want to tell me, and I have no objection to hearing it.”
This was invitation enough.
The second text file to be read in (and its words added to the lexicon) is the file sample2.txt
below:
You can see zebras and yaks at the zoo.
Yes, zebras and yaks and wombats too.
You will also meet a fat cat, wearing a hat, sitting on a mat, reading a map
while drinking from a cup.
What is a word?
A word is a sequence of letters. Words will be treated in a case-insensitive manner. A simple
option is to stored all the words in lower case. Initially, a word is obtained as a sequence of
characters separated by whitespace characters. Then numbers and punctuation characters, if any,
must be removed. More specifically,
• If the word “and” occurs twice in the file, it is only stored once in the lexicon
• If the word “you” also occurs as “YOU”, only one version is stored.
• Punctuation, such as commas, quotes, hyphens, full stops and question marks, are removed.
• If the word “don’t” or the word “second-hand” appears in the input texts, they would be
stored without punctuation, i.e. “dont” and “secondhand” respectively.
• The ‘word’ “1”, for example, will be ignored as it contains numeric characters.
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Saving the lexicon
The words from the created lexicon are to be written to file sample3.txt. These words must be
in sorted in alphabetical order.
The information on each word, which is also written to the text file, includes the frequency
and the list of its neighbors. The list of neighbors must also be in alphabetical order.
The format must be as shown in the example below for a number of words.
a 11 [i]
about 1 []
acknowledged 1 []
all 1 []
also 1 []
and 6 []
answer 1 []
at 2 [it]
austen 1 []
be 2 [by, he, me]
been 1 []
bennet 3 []
but 1 []
by 1 [be, my]
can 1 [cat, man]
cat 1 [can, fat, hat, mat]
chapter 1 []
considered 1 []
cried 1 []
cup 1 []

For each word, first the spelling of the word is displayed, followed by the frequency, and then
followed by the word’s neighbors (in alphabetical order, inside a pair of square brackets).
Task 2
For this task, you are to write the program WordMatchTester.java. This program will
1. Read two text files, sample1.txt a nd sample2.txt, and construct a lexicon that
contains words from the two files (as in Task 1);
2. Find the words that match a pattern, which is input via the command-line argument,
and display the results (the pattern, matching words and frequencies) on the screen. For
example, if the program WordMatchTester.java is compilable and runnable,
java WordMatchTester ma?
is supposed to print the results corresponding to the pattern ma?.
Further information about the task is given below.
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Finding matching words
The patterns to match the words in the lexicon are to be included (hard-coded) as strings in the
test program. A pattern consists of a sequence of letters, with no spaces within the sequence. In
addition, there are two wildcard characters allowed. A ’?’ symbol in the pattern can match with
any one character in a word, while a ’*’ symbol can match with any number of characters in a
word (zero or more).
For each pattern, the pattern and the words that match the pattern are to be displayed on the
screen and write to the text file. Each matching word, together with its frequency, appears on a
separate line. The words are in alphabetical order.
For example, the pattern:
ma?
may result in the words below being displayed to the screen
man 2
map 1
mat 1
may 1
The pattern:
?o?
may result in the following words being displayed. Note the words are displayed in lexicographic
order.
for 1
not 2
too 1
you 5
zoo 1
The pattern:
Mr*
may result in the output:
mr 3
mrs 1
The pattern:
i*
may result in the output:
i 1
impatiently 1
in 3
invitation 1
is 5
it 5
5
The pattern
?ear*
may result in the output:
dear 1
heard 1
hearing 1
wearing 1
Any pattern that has no matches will result in the message
No words in the lexicon match the pattern
output to the screen and written to the file.
Your program is supposed to support ANY pattern. As a suggestion, you should test
your program with at least 10 different patterns according to the description above.
A suggestion
It is up to you to decide on how to organize your code. However, to make your code easier to write
and to test, you may want to have a class called Helper, and in this class you may put methods
such the one to determine if two strings are neighbors of each other, etc. Besides, if it is difficult
for you to come up a way to implement pattern matching, try to recall the knowledge about
Regular Expression, which is supposed to be covered in CSE1/4IOO.
Marking Scheme
Your assignment is to be marked according to a marking sheet. Please check the example
marking sheet on the LMS subject page for details.
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