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Ceng213 – Data Structures
Programming Assignment 1 : Linked Lists and a Simple
Social Network

1 Objectives
In this programming assignment, you are first expected to implement a doubly linked list data
structure, in which each node will contain the data and two pointers to the previous and the
next nodes. The linked list data structure will include a head and a tail pointer that points to
the first and the last nodes of the linked list. The details of the structure are explained further
in the following sections. Then, you will use this specialized linked list structure to implement a
simple social network application.

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Ceng213 – Data Structures
Programming Assignment 1 : Linked Lists and a Simple
Social Network

1 Objectives
In this programming assignment, you are first expected to implement a doubly linked list data
structure, in which each node will contain the data and two pointers to the previous and the
next nodes. The linked list data structure will include a head and a tail pointer that points to
the first and the last nodes of the linked list. The details of the structure are explained further
in the following sections. Then, you will use this specialized linked list structure to implement a
simple social network application.
Keywords: C++, Data Structures, Linked List, Doubly Linked List, Social Network
2 Linked List Implementation (50 pts)
The linked list data structure used in this assignment is implemented as the class template
LinkedList with the template argument T, which is used as the type of the data stored in the
nodes. The node of the linked list is implemented as the class template Node with the template
argument T, which is the type of the data stored in nodes. Node class is the basic building block
of the LinkedList class. LinkedList class has two Node pointers in its private data field (namely
head and tail) which point to the first and the last nodes of the linked list.
The LinkedList class has its definition and implementation in LinkedList.h file and the Node
class has its in Node.h file.
2.1 Node
Node class represents nodes that constitute linked lists. A Node keeps two pointers (namely prev
and next) to its previous and next nodes in the list, and the data variable of type T (namely
data) to hold the data. The class has two constructors, and the overloaded output operator.
They are already implemented for you. You should not change anything in file Node.h.
2.2 LinkedList
LinkedList class implements a doubly linked list data structure with the head and the tail
pointers. Previously, data members of LinkedList class have been briefly described. Their use
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will be elaborated in the context of utility functions discussed in the following subsections. You
must provide implementations for the following public interface methods that have been declared
under indicated portions of LinkedList.h file.
2.2.1 LinkedList();
This is the default constructor. You should make necessary initializations in this function.
2.2.2 LinkedList(const T arr[], int arrSize);
This constructor takes an array of T objects (arr) and the size of the arr array (arrSize) as
parameters. You should make necessary initializations, create new nodes by copying the T objects
in given arr array and insert new nodes into the linked list.
2.2.3 LinkedList(const LinkedList<T &obj);
This is the copy constructor. You should make necessary initializations, create new nodes by
copying the nodes in given obj and insert new nodes into the linked list.
2.2.4 ∼LinkedList();
This is the destructor. You should deallocate all the memory that you were allocated before.
2.2.5 Node<T *getFirstNode() const;
This function should return a pointer to the first node in the linked list. If the linked list is
empty, it should return nullptr.
2.2.6 Node<T *getLastNode() const;
This function should return a pointer to the last node in the linked list. If the linked list is
empty, it should return nullptr.
2.2.7 Node<T *getNode(const T &data) const;
You should search the linked list for the node that has the same data with the given data and
return a pointer to that node. You can use operator== to compare two T objects. If there exists
no such node in the linked list, you should return nullptr.
2.2.8 int getNumberOfNodes() const;
This function should return an integer that is the number of nodes in the linked list.
2.2.9 bool isEmpty() const;
This function should return true if the linked list is empty (i.e. there exists no nodes in the
linked list). If it is not empty, it should return false.
2.2.10 bool contains(Node<T *node) const;
This function should return true if the linked list contains the given node node (i.e. any
next/prev in the list matches with node). Otherwise, it should return false.
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2.2.11 void insertAtTheHead(const T &data);
You should create a new node with given data and insert it at the beginning of the linked list
as the first node. Don’t forget to make necessary pointer, and head-tail modifications.
2.2.12 void insertAtTheTail(const T &data);
You should create a new node with given data and insert it at the end of the linked list as the
last node. Don’t forget to make necessary pointer, and head-tail modifications.
2.2.13 void insertSorted(const T &data);
You should create a new node with given data and insert it to the appropriate place of the linked
list. For this function, you may assume that the linked list will be already sorted in ascending
order with respect to the data values of its nodes and you should keep the linked list sorted
after making the insertion. You may also assume that there will be no nodes with duplicate
data in the linked list. You can use overloaded relational operators (i.e. operator<, operator,
operator<=, operator=) to compare two T objects. Don’t forget to make necessary pointer,
and head-tail modifications.
2.2.14 void removeNode(Node<T *node);
You should delete the given node node from the linked list. Don’t forget to make necessary
pointer, and head-tail modifications. If the given node node is not in the linked list (i.e. the
linked list does not contain the given node node), do nothing.
2.2.15 void removeNode(const T &data);
You should delete the node that has the same data with the given data from the linked list.
Don’t forget to make necessary pointer, and head-tail modifications. If there exists no such node
in the linked list, do nothing.
2.2.16 void removeAllNodes();
You should remove all nodes in the linked list so that the linked list becomes empty.
2.2.17 T *toArray() const;
You should return an array containing the data of all nodes of the linked list from first node’s
data to last node’s data. If the linked list is empty, it should return nullptr.
2.2.18 LinkedList<T &operator=(const LinkedList<T &rhs);
This is the overloaded assignment operator. You should remove all nodes in the linked list and
then create new nodes by copying the nodes in given rhs and insert new nodes into the linked
list.
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3 Social Network Implementation (50 pts)
The social network in this assignment is implemented as the class SocialNetwork. SocialNetwork
class has two LinkedList objects in its private data field (namely profiles and posts) with
the types Profile and Post, respectively. These two LinkedList objects keep the profiles and
posts of the social network. Profile class represents the users of the social network and Post
class represents the messages shared by the users of the social network.
The SocialNetwork, Profile and Post classes has their definitions in SocialNetwork.h, Profile.h
and Post.h files and their implementations in SocialNetwork.cpp, Profile.cpp and Post.cpp files,
respectively.
3.1 Profile
Profile objects keep firstname, lastname and email variables of type std::string to hold
the data related with the users of the social network. They also keep linked lists of pointers to
the profiles of the user’s friend (namely friends), pointers to the posts liked by the user (namely
likes), and pointers to the posts by the user (namely posts). Profile and Post pointers in this
three linked lists are pointers to the data variables of the nodes in SocialNetwork class. Most
of the functions of Profile class are already implemented for you. In Profile.cpp file, you need
to provide implementations for following functions declared under Profile.h header to complete
the assignment. You should not change anything in file Profile.h.
3.1.1 bool operator==(const Profile &rhs) const;
This is the overloaded equality operator. You should compare Profile objects by firstname,
lastname, and email variables. If all three variables are equal, this function should return true.
Otherwise, it should return false.
3.1.2 bool operator<(const Profile &rhs) const;
This is the overloaded less than comparison operator. You should compare Profile objects by
firstname and lastname variables. If lastname is lexicographically less than the lastname of
rhs, return true. If they are same and firstname is lexcographically less than the firstname
of rhs, return true. Otherwise, return false.
3.2 Post
Post objects keep message variable of type std::string and postId variable of type int to
hold the data related with posts of the users of the social network. Most of the functions of Post
class are already implemented for you. In Post.cpp file, you need to provide implementations for
following functions declared under Post.h header to complete the assignment. You should not
change anything in file Post.h.
3.2.1 bool operator==(const Post &rhs) const;
This is the overloaded equality operator. You should compare Post objects by message and
postId variables. If both variables are equal, this function should return true. Otherwise, it
should return false.
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3.2.2 bool operator<(const Post &rhs) const;
This is the overloaded less than comparison operator. You should compare Post objects by
postId variable. If postId is less than the postId of rhs, return true. Otherwise, return
false.
3.3 SocialNetwork
In SocialNetwork class, all member functions should utilize profiles, and posts member
variables to operate as described in the following subsections. In SocialNetwork.cpp file, you
need to provide implementations for following functions declared under SocialNetwork.h header
to complete the assignment.
3.3.1 void addProfile(const std::string &firstname, const std::string &lastname,
const std::string &email);
This function adds a new profile (i.e. registers a new user). It takes profile information
(firstname, lastname and email) as parameter and inserts a new Profile object to the
profiles linked list. You should use insertSorted() function for insertion. For this function, you may assume that the given email is not already registered.
3.3.2 void addPost(const std::string &message, const std::string &email);
This function adds a new post. It takes post information (message) and the owner profile’s email
(email) as parameters and inserts a new Post object to the posts linked list. It also marks/adds
the new post as a post by user with given email by populating the corresponding profile object’s
posts list. You should use insertAtTheTail() function for both insertions. For this function,
you may assume that the given email is already registered.
3.3.3 void deleteProfile(const std::string &email);
This function deletes an already registered user (i.e. profile). It takes email of a profile (email)
as parameter. Deletion of a user includes some steps, which are deleting the user from its friends’
list of friends, deleting the user’s posts from other users’ list of likes, deleting content of the user’s
Profile object, finally deleting the user’s Profile object from the SocialNetwork. For this
function, you may assume that the given email is already registered.
3.3.4 void makeFriends(const std::string &email1, const std::string &email2);
This function marks/adds two profiles (i.e. users) as friends with each other. It takes emails
of two users (email1 and email2) as parameters and makes them friends by populating their
Profile objects’ friends lists. For this function, you may assume that the given emails are
different and they are already registered. You may also assume that they are not friends yet.
3.3.5 void likePost(int postId, const std::string &email);
This function marks a post as liked by a user. It takes id of a post (postId) and email of a profile
(email) as parameters and marks that post as liked by that user by populating the corresponding
Profile object’s likes list. For this function, you may assume that the given email is already
registered, and there exists a post with given id. You may also assume that the post is not liked
by the user yet.
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3.3.6 void unlikePost(int postId, const std::string &email);
This function makes a user unlike a post. It takes id of a post (postId) and email of a profile
(email) as parameters and removes corresponding Post pointer from the corresponding Profile
object’s likes list. For this function, you may assume that the given email is already registered,
and there exists a post with given id. If the post is not already liked by the user, do nothing.
3.3.7 LinkedList<Profile * getMutualFriends(const std::string &email1, const
std::string &email2);
This function returns a linked list of pointers to the corresponding Profile objects of the mutual
friends of two users with given emails (email1 and email2). List of mutual friends should have
the same order as they exist in the first user’s list of friends. For this function, you may assume
that the given emails are different and they are already registered.
3.3.8 LinkedList<Post * getListOfMostRecentPosts(const std::string &email, int
k=0);
This function returns a linked list of pointers to the corresponding Post objects of the k most
recent posts of the user with given email (email). List of posts should be sorted from latest post
to earliest post. For this function, you may assume that the given email is already registered.
4 Driver Programs
To enable you to test your LinkedList and SocialNetwork implementations, two driver programs, main linkedlist.cpp and main socialnetwork.cpp are provided. Their expected outputs
are also provided in output linkedlist.txt and output socialnetwork.txt files, respectively.
5 Regulations
1. Programming Language: You will use C++.
2. Standard Template Library is not allowed.
3. External libraries other than those already included are not allowed.
4. Those who do the operations (insert, remove, get) without utilizing the linked list will
receive 0 grade.
5. Those who modify already implemented functions and those who insert other data variables
or public functions and those who change the prototype of given functions will receive 0
grade.
6. Those who use STL vector or compile-time arrays or variable-size arrays (not existing in
ANSI C++) will receive 0 grade. Options used for g++ are “-ansi -Wall -pedantic-errors
-O0 -std=c++11”. They are already included in the provided Makefile.
7. You can add private member functions whenever it is explicitly allowed.
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8. Late Submission Policy: Each student receives 5 late days for the entire semester. You
may use late days on programming assignments, and each allows you to submit up to 24
hours late without penalty. For example, if an assignment is due on Thursday at 11:30pm,
you could use 2 late days to submit on Saturday by 11:30pm with no penalty. Once a
student has used up all their late days, each successive day that an assignment is late will
result in a loss of 5% on that assignment.
No assignment may be submitted more than 3 days (72 hours) late without permission
from the course instructor. In other words, this means there is a practical upper limit
of 3 late days usable per assignment. If unusual circumstances truly beyond your control
prevent you from submitting an assignment, you should discuss this with the course staff
as soon as possible. If you contact us well in advance of the deadline, we may be able to
show more flexibility in some cases.

6 Submission
• Submission will be done via CengClass (cengclass.ceng.metu.edu.tr).
• Don’t write a main function in any of your source files.
• A test environment will be ready in CengClass.
– You can submit your source files to CengClass and test your work with a subset of
evaluation inputs and outputs.
– Additional test cases will be used for evaluation of your final grade. So, your actual
grades may be different than the ones you get in CengClass.
– Only the last submission before the deadline will be graded.
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