CSCI 1300辅导、讲解C/C++程序、辅导C/C++、讲解Starting Computing留学生
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Instructor: Fleming
Homework 8: Part III
**This assignment is a project!
Due Monday, November 5th
, by 11:55 pm
**No bonus for project II !
This assignment is due Monday, November 5th
, by 11:55 pm
● All components (Cloud9 workspace, moodle quiz attempts, and zip file) must be
completed and submitted by Monday, November 5th
, by 11:55 pm for your
homework to receive points.
Objectives:
● Practice implementing classes
● Develop proper techniques for object-oriented programming
● Manipulate arrays of objects
● Implement classes which have objects from other classes as data members
Problem Set **All the examples and values used in examples are imaginary and randomly generated.
In part 3 you will streamline your implementation with the addition of a library class. This
class will centralize many of the methods you implemented in parts 1 and 2 and provide
more functionality, including the ability to recommend books based on the similarity of
two users.
Specifications
● Create a new class Library. Define the class in a header file and implement the
class in a cpp file.
● The Book and User classes from Homework 7 will be part of Homework 8 as well
● In main() create an instance of Library object and a menu as specified
● Students should have seven files (Book.h, Book.cpp, User.h, User.cpp, Library.h,
Library.cpp, Hmwk8.cpp)
● The name of each member function should be exactly as specified. If you modify
the function names your solution will not pass the autograder.
Library Class
**You should have separate files for class definition and implementation: Library.h and Library.cpp
Create a class Library, with separate interface and implementation, comprised of the
following attributes:
Data members (private):
Book array: books An array of Book objects
User array: users An array of User objects
int: numBooks Number of books in the database (library)
int: numUsers Number of users in the database (library)
int: sizeBook The capacity of the books array (200). Constant
int: sizeUser The capacity of the users array (200). Constant
Member functions (public):
Default constructor Sets both numBooks and numUsers to value 0.
readBooks(string) Takes a string (the name of the file to be read) and
populates the books array. Returns the total
number of books in books array as an integer
readRatings(string) Takes a string (the name of the file to be read) and
populates the users array. Returns the total
number of users in users array as an integer
printAllBooks() Prints all books stored in books array.
getCountReadBooks(string) Takes a string (username) and returns the number
of books read by that user as an integer.
calcAvgRating(string) Takes a string (the title of a book) and returns the
average rating of the specified book as a double
addUser(string) Takes a string (username) and returns True if the
username is successfully added to the database.
Otherwise, returns False.
checkOutBook(string,
string, int)
Takes two strings and an integer for username, title
of book, and a new rating, respectively (in this
order). Returns True if the rating is successfully
updated. Otherwise, returns False.
viewRatings(string) Takes a string (username) and prints all the books
a user has provided ratings for.
getRecommendations(string) Takes a string username and prints the first 5 book
recommendations from the most similar (other)
user.
It is advisable to write your own test cases for each class. Test your class in Cloud9 before
submitting to the autograder, as the autograder has a submission limit of 20 tries every 24
hours.
Problem 1 - the member function readBooks
The member function readBooks populates an array of Book objects with the title and
author data found in a file similar to the file books.txt. The array of Book objects is one of
the data members of the Library class. This function should:
● Accept one input argument:
○ string: the name of the file to be read
● Use ifstream, split(), and getline to read and parse data from the file.
● For each line in the file:
○ fill in the author and title data members for a Book object, at the
appropriate index in the array of Book objects.
● Also:
○ Update the total number of books in the system(from all the files read so
far, see the “Important” note below)
● Return the total number of books in the system, as an integer.
● If the file contains more books than “empty” slots available in the books array,
only write enough books so that you do not exceed the capacity of the array.
● If the file cannot be opened, return -1
Important: when testing your readBooks function, make sure it supports multiple
reads from different .txt files in a row. For example, you should be able to call the
function to read the file books1.txt , and then call the function again to read the file
book2.txt. The result should be an array of Book objects, with the books from the first
file, followed by the books from the second file.
Problem 2 - the member function readRatings
The member function readRatings populates an array of User objects with the user name
and the ratings data found in a file similar to the file ratings.txt. The array of User
objects is one of the data members of the Library class. This function should:
● Accept one input argument:
○ string: the name of the file to be read
● Use ifstream, split(), and getline to read and parse data from the file.
● For each line in the file:
○ fill in the username and ratings data members for a User object, at
the appropriate index in the array of User objects.
● Also:
○ Update the total number of users in the system(from all the files read so
far, see the “Important” note below)
● Return the total number of users in the system, as an integer.
● If the file contains more users than “empty” slots available in the users array,
only write enough books so that you do not exceed the capacity of the array.
● If the file cannot be opened, return -1
Important: when testing your readRatings function, make sure it supports multiple
calls in a row. For example, you should be able to call the function to read the file
ratings1.txt , and then call the function again to read the file ratings2.txt. The result
should be an array of User objects, with the users from the first file, followed by the
users from the second file.
Expected output:
cynthia...
diane...
joan...
barbara...
(etc.)
Problem 3 - the member function printAllBooks
The member function printAllBooks prints the list of all the books in the database
(library). This function should:
● Accept no arguments
● Not return anything
● If the program has not read any books files or any ratings files, print the following
message:
Database has not been fully initialized
● Otherwise, print “Here is a list of books”, followed by each book in the
following format
<book title > by <book author>
Expected output (assuming you have read the data only from books.txt)
Here is a list of books
The Hitchhiker's Guide To The Galaxy by Douglas Adams
Watership Down by Richard Adams
The Five People You Meet in Heaven by Mitch Albom
Speak by Laurie Halse Anderson
(etc.)
Problem 4 - the member function getCountReadBooks
The member function getCountReadBooks determines how many books a particular
user has read and reviewed. This function should:
● Accept one argument:
○ string: username
● Return the number of books read/reviewed by the specified user, as an integer.
● If the program has not read any books files or any ratings files, it should return -1
after printing the following message:
Database has not been fully initialized
● If the database is initialized (at least one file of books and at least one file of
ratings has been read), but the user name is not found, return -2 after printing the
following message :
<username> does not exist in the database
Problem 5 - the member function calcAvgRating
The member function calcAvgRating returns the average (mean) rating for a particular
book. This function should:
● Accept one argument:
○ string: book title
● Return the average rating of the specified book as a double
● If the program has not read any books files or any ratings files, it should return -1
after printing the following message:
Database has not been fully initialized
● If the database is initialized (at least one file of books and at least one file of
ratings has been read), but the book is not found, return -2 after printing the
following message:
<bookTitle> does not exist in the database
Note: Books that haven’t been read shouldn’t be counted in calculating the average.
Problem 6 - the member function addUser
The member function addUser adds a new user to the database. This function should:
● Accept one argument:
○ string: user name
● Fill in the username and ratings data members for a User object, at the
appropriate index in the array of User objects. :
● Update the total number of users in the system(from all the files read so far, see
the “Important” note below)
● The name of the user is case insensitive (e.g. Ben. BEN, ben are all same as
ben)
● Return True if the user is successfully added.
● If the user already exists in the database, print the following message and return
False
<username> already exists in the database
● If the database is full (the array of User objects is full), print the following
message and return False
Database full
Problem 7 - the member function checkOutBook
The member function checkOutBook updates the rating of the book for the user. This
function should:
● Accept three arguments in this order
○ string : username
○ string: book title
○ int: new rating
● Find the index of the user and the index for the book, then update the new rating
if the new rating value is valid. The rating scheme follows the one provided in
homework 6.
Rating Meaning
0 Did not read
1 Hell No - hate it!!
2 Don’t like it.
3 Meh - neither hot nor cold
4 Liked it!
5 Mind Blown - Loved it!
● If the program has not read any books files or any ratings files, it should return
False after printing the following message:
Database has not been fully initialized
● If the rating is successfully updated, then returns True. Otherwise, it shows one
(or more) of the following messages in the given order and return False.
● If the user is not found:
<username> does not exist in the database
● If the title is not found:
<bookTitle> does not exist in the database
● If the rating value is not valid:
<newRatingValue> is not valid
Problem 8 - the member function viewRatings
The member function viewRatings prints all the books a user has provided ratings
for. Recall that a rating of 0 means a user has not rated that book and hence shouldn’t
be displayed. This function should:
● Accept one input argument:
○ string: username
● Not return anything.
● If the program has not read any books files or any ratings files, print the following
message:
Database has not been fully initialized
● If the user is not found in the database, print:
<username> does not exist in the database
● If the user is found in the database, but has not rated any books, print:
<username> has not rated any books yet
● If the user exists in the database, and it has rated at least one book, display the
user’s ratings in the following format:
Expected output (assuming you have read the data only from
books.txt,ratings.txt)
Here are the books that megan rated
Title : The Hitchhiker's Guide To The Galaxy
Rating : 5
-----
Title : The Five People You Meet in Heaven
Rating : 2
-----
(...)
Problem 9 - the member function getRecommendations
The member function getRecommendations will recommend book titles a user might
enjoy, based on the user’s similarity of ratings with another user. This function should:
● Accept one input argument:
○ string: username
● Not return anything.
● If the program has not read any books files or any ratings files, it should print the
following message:
Database has not been fully initialized
● If the database is initialized (at least one file of books and at least one file of
ratings has been read), but the user name is not found, it should print the
following message :
<username> does not exist in the database
To generate recommendations for a user, for example the user named “ben”:
1. Find the most similar user to “ben”. Let’s say we found “claire” to be most
similar.
2. Recommend to “ben” the first 5 books in the database “claire” has rated with a
rating of 3, 4 or 5, that “ben” has not yet read (rating 0)
○ If there are less than 5 books to recommend, recommend as many as
possible. “ben” will be presented with 0 to 5 recommendations.
To find out who the most similar user is to “ben”, we need to compare “ben”’s ratings
with the ratings from all the other users. We need to look at differences in the rating
values between the two users for a certain book, add them up, and come up with a
similarity value. The user who has the smallest similarity value, will be the user most
similar to “ben”.
Note 1: A new user, who has not rated any books, cannot be chosen as the most
similar user. We recommend you use the getCountReadBooks function to weed out
the new users.
Note 2: You can assume there will be no ties between two users.
The similarity metric you should use is the sum of squared differences (SSD).
The sum of squared differences is calculated by summing the squares of the
differences between corresponding elements in two ratings arrays from two users.
Follow the example below.
Let A represent ben's ratings, and B represent claire's ratings.
Ai is ben's rating for book i, and Bi is claire's rating for book i
SSD = ∑(A )
i
i ? Bi
2
For example:
john′s ratings : [0, 1, 3, 5]
claire′s ratings : [3, 0, 5, 0]
SSD = (0 ? 3) (1 0) (3 5) (5 0) 2 + ? 2 + ? 2 + ? 2
SSD = (? 3) (1) (? ) (5) 2 + 2 + 2 2 + 2
SSD = 9 + 1 + 4 + 25 = 39
Users with very different ratings will get a high SSD.
john′s ratings : [5, 1, 0, 0, 5]
david′s ratings : [1, 5, 0, 5, 1]
SSD = (5 ? 1) (1 5) (5 0) 2 + ? 2 + ? 2 + (5 ? 1) 2
SSD = 4 4 5 2 + 2 + 2 + 4 2
SSD = 16 + 16 + 25 + 16 = 73
Two users with very similar ratings will get a low SSD.
john′s ratings : [5, 0, 5, 3]
claire′s ratings : [5, 0, 4, 2]
SSD = (5 ? 5) (5 4) (3 2) 2 + ? 2 + ? 2
SSD = 0 1 1 2 + 2 + 2
SSD = 0 + 1 + 1 = 2
For example (this example is different than the data in ratings.txt):
Let's say we're generating recommendations for John. Here are the books:
Douglas Adams,The Hitchhiker's Guide To The Galaxy
Richard Adams,Watership Down
Mitch Albom,The Five People You Meet in Heaven
Laurie Halse Anderson,Speak
Liz: [5, 0, 5, 3]
John: [5, 0, 3, 0]
David: [4, 1, 0, 5]
To generate recommendations for John:
1. find the most similar user
John has a SSD of 13 with Liz and an SSD of 36 with David, so John is more
similar to Liz.
2. find 10 books Liz (the most similar user) has rated as a 3, 4, or 5 that John
has not yet read (rating 0)
We look at Liz's list to find books that she's rated that John hasn't rated yet:
? Liz has rated The Hitchhiker's Guide To The Galaxy as a 4, but
John has already rated this book.
? Liz has rated Watership Down as 1, but the rating is too low.
? Liz hasn’t rated The Five People You Meet in Heaven
? Liz has rated Speak as a 5. John hasn't read that book yet, so we add it
to the list of recommendations.
There are no more books that Liz has rated, so we're done. Our final list of
recommendations will be:
speak by laurie halse anderson
Here are examples of output in different situations:
● If there are no books to recommend for a certain user, print the following:
There are no recommendations for <username> at the present
● If there is at least one book to recommend for a certain user, print the following:
Here are the list of recommendations:
<book_title_1> by <author1>
<book_title_2> by <author2>
…
…
<book_title_5> by <author5>
Driver function
In addition to the menu functionality used in the Homework 6 and 7, we need to add 4
more options. You can find the updated displayMenu function in Hmwk8.cpp on Moodle.
Menu options:
1. Read book file
○ Prompt the user for a file name
○ Pass the file name to your readBooks function.
○ After the function returns, print the total number of books in the database:
Total books in the database: <numberOfBooks>
○ If no books are saved to the database due to wrong file name, then print
the following message:
No books saved to the database
2. Read user file
○ Prompt the user for a file name.
○ Pass the file name to your readRatings function
○ After the function returns, print the total number of users in the database:
Total users in the database: <numberOfUsers>
○ If no books are saved to the database due to wrong file name, then print
the following message:
No users saved to the database
3. Print book list
○ Call your printAllBooks function.
4. Find number of books user rated
○ Prompt the user for a username.
○ Pass the username to your getCountReadBooks function
○ If the user exists in the system, print the result in the following format:
<name> rated <numBookRead> books
5. Get average rating
○ Prompt the user for a title.
○ Pass the title to your calcAvgRating function
○ If the title exists in the database, print the result in the following format:
The average rating for <bookTitle> is <value>
Note: <value> is a double with 2 decimal points.
6. Make a new account
○ Prompt the user for a username:
Enter a username:
○ Pass the username to your addUser function
○ Based on the return value from the addUser function, you need to print a
message. If the user has successfully been added to the database, print:
Welcome to the library <user name>
○ If the user was not added to the database, print:
<user name> could not be added in the database
7. Check Out Book
○ Prompt the user for the username, the title of a book, and the new rating
Enter a username:
Enter a book title:
Enter a rating for the book:
○ Pass the username, the title, and the new rating to your checkOutBook
function
○ Based on the return value from the checkOutBook function, you need to
print a message. If the book has successfully been read and rated, print:
We hope you enjoyed your book. The rating has been updated
○ If the book has not successfully been read and rated, print:
<user_name> could not check out <book_title>
8. View Ratings
○ Prompt the user for a username
Enter a username:
○ Pass the username and the title to your viewRating function
9. Get recommendations
○ Prompt the user for a username
Enter a username:
○ Pass the username to your getRecommendations function
10.Quit