Assignment 03 Solution

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Description

You will implement and test a revised sequence class that uses a linked list to store the items.

Purposes:

Ensure that you can write a small class that uses the linked list toolkit to create and manipulate a linked list.

Before Starting:

Read all of Chapter 5, with particular attention to Sections 5.3 and 5.4.

Due Date:

Wednesday, October  19, 2016. If you have problems, late work will be accepted on Thursday with no penalties. Late work may be submitted on Friday or Saturday with 5% penalty per day. No work will be accepted after Saturday.

How to Turn In:

Please submit homeworks using this link. On the upload page, you can select the file(s) you want to submit (multiple files can be selected by pressing down CTRL key while selecting the files). Then enter your last name and the last 4 digit of your student ID (from CUNYfirst, NOT your SSN!!!). Once successfully submitted, it will show a page with RECEIPT NUMBER, save that number or that page because you will need it to retrieve your grade for that assignment. You can submit your assignment as many times as you want before the deadline, only the latest one will be graded.

 

To retrieve your grade for an assignment (after I finish grading it), please go to the download page here, select the assignment, enter the receipt number for that assignment, your last name and your last 4 digit of your student ID. The page will then download a TXT file which contain your graded submission.

Files that you must write and turn in:

sequence3.h: The header file for the new sequence class. Actually, you don’t have to write much of this file. Just start with our version and add your name and other information at the top. If some of your member functions are implemented as inline functions, then you may put those implementations in this file too. By the way, you might want to compare this header file with your first sequence header file (sequence1.h) , and second sequence header file (sequence2.h). The linked list version no longer has a CAPACITY constant nor a DEFAULT_CAPACITY constant because the items are stored on a linked list instead of an array.

sequence3.cxx: The implementation file for the new sequence class. You will write all of this file, which will have the invariant of the sequence class, the implementations of all the member functions of the sequence class, and the Big-Os of these functions.

node1.h and node1.cxx: Copy these files to your sub-directory. They contain the linked list toolkit from Section 5.2. You may use these files without changing them. However we only provide the documentation for the function list_piece (see Self-Test Exercise 17 on page 239). You may need to write an implementation of this function if you are going to use it in writing your copy constructor and overloading your assignment operator. If you do make changes, please turn them in.

Other files that you may find helpful:

sequence_test.cxx: This is the same interactive test program that you used with the earlier sequences. This is exactly what we expect for the  information hiding of the class – the users do not need to know how the class is implemented ( both the member variables and the functions) as far as the interfaces (the prototype of the member functions)  remain the same. So if you want to use the test program with the new sequence, the only thing you need to do is to copy it to your directory and open it with your editor. Then change the statements

 

#include “sequence1.h”

using namespace main_savitch_3;

to

#include “sequence3.h”

using namespace main_savitch_5;

 

seq_ex3.cxx: A non-interactive test program that will be used to grade the correctness of your new sequence class. The points given by the program will only be served as a reference; we are going to look into your code and your analysis ( in the form of comment lines) for actual grading.

The sequence Class Using a Linked List

Discussion of the Assignment

 

Your sequence class for this assignment will differ from the your previous sequence in the following ways:

The sequence’s items are now stored on a linked list. The head pointer of the linked list is a private member variable of the sequence class. I suggest that you also have a tail pointer as an additional private member variable of the sequence class. The reason for the tail pointer is explained in Section 5.4 of the textbook.

Because you are dynamically allocation memory within your sequence class, you will need to define a copy constructor, an assignment operator, and a destructor. You need to pay special attention to the value semantics of your new sequence class – you need not only to make a copy of the linked list, but also need to place the node pointers correctly. Please refer to page 260 for more detailed discussions on the value semantics.

Start by declaring the new sequence’s private member variables in sequence3.h. You might try declaring these variables yourself, and then compare your solution with the suggestion in Section 5.4.

Once again, do your work in small pieces. For example, my first version of the sequence had only a constructor, start, insert, advance, and current. My other member functions started out as stubs.

 

Design a sequence class using a linked list could be little bit more complicated than using an array. Therefore, I recommend you to draw an example linked list such as the one shown in page 260 of the textbook when you are writing code for each member function. Always remember to show all the member variables in order to remind you  making proper changes of them. You need to place the cursor and the precursor at various locations, head, tail and other places. Note that the sequence could be empty, and cursor and/or precursor could be NULL, even when the sequence is NOT empty. With the help of small drawings, jobs will be much easier!

 

Use the interactive test program and the debugger to track down errors in your implementation. If you have an error, do not start making changes until you have identified the cause of the error. If you come to me  for help, we will always ask you to do the following:

 

Show us the invariant that describes how your private member variables implement the sequence class.

Use the debugger to show us the problem!

For those working in the Unix operating system: Spend some time writing your make file. A correct Unix makefile will save you time. Make sure that each compilation command in the make file has a TAB as the first character. In order to insert a TAB using emacs, type Ctrl-Q and then press the TAB key. Or, if you are working from a modem where the TAB key is disabled, you can type

ESCAPE x quoted-insert RETURN TAB

Run Time Analysis of the sequence classes and grading rules

 

We will use the number of items in a bag as the input size n.  Please give the Big-O of each function in your implementation, and compare them with the corresponding functions of the sequence using a dynamic array. You should write the time analysis in the comment lines of each function.  The breakdowns of points (of 100) will be the followings

 

Basis points (70) if your implementation passes the seq_ex3 test

Invariant of the class (5 points)

Run time analysis (10 points)

Other implementation details (15 points)