Assignment 3 Communication Between Towers

Assignment 3 - Linked Lists
Communication Between Towers
OBJECTIVES
1. Create, traverse, add, reverse and delete from a linked list
2. Get practice implementing classes
Background
In the Lord of the Rings trilogy, there is a scene where a warning beacon is lit in the towers of
Minas Tirith, which is seen by a second beacon, prompting them to light their own fire which a
third beacon sees, and so forth. This was a rapid means of communication in the days before
telegraphs were invented. In this assignment, you’re going to simulate a communications
network using a linked list. Each node in the list will represent a country and you need to be able
to send a message between nodes from one side of the world to the other.
Building your own communications network
You will be implementing a class to simulate a linear communication network between
countries. There are three files in Moodle containing a code skeleton to get you started. Do not
modify the header file or your code won’t work in Moodle! You will have to complete both the
class implementation in CountryNetwork.cpp and the driver file main.cpp.
The linked-list itself will be implemented using the following struct (already included in the
header file):
struct Country
{
string name; // name of the country
string message; // message this country has received
int numberMessages; // no. of messages passed through this country
Country *next; // pointer to the next country
};

Class Specifications
The CountryNetwork class definition is provided in the file CountryNetwork.hpp in Moodle. Do
not modify this file or your code won’t work on Moodle! Fill in the file CountryNetwork.cpp
according to the following specifications.
Country* head;
➔ Points to the first node in the linked list
CountryNetwork();
➔ Class constructor; set the head pointer to NULL
bool isEmpty();
➔ Return true if the head is NULL, false otherwise
void insertCountry(Country* previous, string countryName); // Beware of edge cases
➔ Insert a new country with name countryName in the linked list after the country pointed
to by previous. If previous is NULL, then add the new country to the beginning of the
list. Print the name of the country you added according to the following format:
// If you are adding at the beginning use this:
cout << "adding: " << countryName << " (HEAD)" << endl;
// Otherwise use this:
cout << "adding: " << countryName << " (prev: " << previous-name <<
")" << endl;
void deleteCountry(string countryName); // Beware of edge cases
➔ Use the member function searchNetwork to find the node with name countryName,
then delete it. If there is no node with name countryName, print "Country does not
exist."
void loadDefaultSetup();
➔ First, delete whatever is in the linked list using the member function
deleteEntireNetwork. Then add the following six countries, in order, to the network with
insertCountry: "United States", "Canada", "Brazil", "India", "China", "Austraila"
Country* searchNetwork(string countryName);
➔ Return a pointer to the node with name countryName. If countryName cannot be
found, return NULL

void deleteEntireNetwork();
➔ Delete every node in the linked list and set head to NULL. Print the name of each node
as you are deleting it according to the following format:
cout << "deleting: " << node-name << endl;
After the entire linked list is deleted, print:
cout << "Deleted network" << endl;
void reverseEntireNetwork();
➔ Manipulate *next pointers to reverse the order of the linked list. For example, reversing
the following list with “A” at the head: “A - B - C - D - NULL”, should yield
“D - C - B - A - NULL” with “D” as the new head
void transmitMsg(string receiver, string msg);
➔ Traverse the linked list from the head to the node with name receiver. For each node in
this path (including the head), set the node’s message to msg and increment the node’s
numberMessages field. If the list is empty, print "Empty list" and exit the function
➔ As you traverse the list, at each node report the message received and the number of
messages received using the following cout: (See the end of this document for example
output)
cout << node-name << " [# messages received: " <<
node-numberMessages << "] received: " << node-message << endl;
void printPath();
➔ Print the names of each node in the linked list. Below is an example of correct output
using the default setup. (Note that you will cout << “NULL” at the end of the path)
== CURRENT PATH ==
United States - Canada - Brazil - India - China - Australia - NULL
===
➔ If the network is empty then print "nothing in path"

Main driver file
Your program will start by displaying a menu by calling the displayMenu function included in
main.cpp. The user will select an option from the menu to decide what the program will do, after
which, the menu will be displayed again. The specifics of each menu option are described
below.
Option 1: Build Network
This option calls the loadDefaultSetup function, then calls the printPath function. You should
get the following output:
adding: United States (HEAD)
adding: Canada (prev: United States)
adding: Brazil (prev: Canada)
adding: India (prev: Brazil)
adding: China (prev: India)
adding: Australia (prev: China)
== CURRENT PATH ==
United States - Canada - Brazil - India - China - Australia - NULL
===
Option 2: Print Network Path
Calls the printPath function. Output should be in the format below:
// Output for the default setup
== CURRENT PATH ==
United States - Canada - Brazil - India - China - Australia - NULL
===
// Output when the linked list is empty
== CURRENT PATH ==
nothing in path
===

Option 3: Transmit Message
Prompt the user for two inputs: a message to send, and the name of a country to receive the
message (Hint: use getline in case there are spaces in the user input). Pass the message and
country name to the transmitMsg function.
For example, the following should be the output if the linked-list contains the default setup from
option (1) and the message “bom dia” is sent to “Brazil”:
Enter name of the country to receive the message:
Brazil
Enter the message to send:
bom dia
United States [# messages received: 1] received: bom dia
Canada [# messages received: 1] received: bom dia
Brazil [# messages received: 1] received: bom dia
If the user then decides to transmit the message “ni hao” to “China”, the output will be:
Enter name of the country to receive the message:
China
Enter the message to send:
ni hao
United States [# messages received: 2] received: ni hao
Canada [# messages received: 2] received: ni hao
Brazil [# messages received: 2] received: ni hao
India [# messages received: 1] received: ni hao
China [# messages received: 1] received: ni hao
Option 4: Add Country
Prompt the user for two inputs: the name of a new country to add to the network, newCountry,
and the name of a country already in the network, previous, which will precede the new
country. Use the member functions searchNetwork and insertCountry to insert newCountry
into the linked-list right after previous.
● If the user wants to add the new country to the head of the network then they should
enter “First” instead of a previous country name.

● If the user enters an invalid previous city (not present in the linked list), then you need to
prompt the user with the following error message and collect input again until they enter
a valid previous country name or “First”:
cout << "INVALID country...Please enter a VALID previous country
name:" << endl;
● Once a valid previous country name is passed and the new country is added, call the
function printPath to demonstrate the new linked-list.
For example, the following should be the output if the linked-list contains the default setup from
option (1) and the user wants to add Colombia after Brazil:
Enter a new country name:
Colombia
Enter the previous country name (or First):
Brazil
adding: Colombia (prev: Brazil)
== CURRENT PATH ==
United States - Canada - Brazil - Colombia - India - China - Australia -
NULL
===
Option 5: Delete Country
Prompt the user for a country name, then pass that name to the deleteCountry function and
call printPath to demonstrate the new linked-list.
For example, the following should be the output if the linked-list contains the default setup from
option (1) and the user wants to delete Canada:
Enter a country name:
Canada
== CURRENT PATH ==
United States - Brazil - India - China - Australia - NULL
===
Option 6: Reverse network
Call the reverseEntireNetwork function then the printPath function.

For example, the following should be the output if the linked-list contains the default setup from
option (1):
== CURRENT PATH ==
Australia - China - India - Brazil - Canada - United States - NULL
===
Option 7: Clear network
Call the deleteEntireNetwork function. For example, deleting the default network should print:
deleting: United States
deleting: Canada
deleting: Brazil
deleting: India
deleting: China
deleting: Australia
Deleted network
Option 8: Quit
Print the following message:
cout << "Quitting... cleaning up path: " << endl;
Then call printPath, followed by deleteEntireNetwork. Now, check if the network is empty
using isEmpty. If it is, print:
cout << "Path cleaned" << endl
Otherwise, print:
cout << "Error: Path NOT cleaned" << endl;
Finally, print the following before exiting the program:
cout << "Goodbye!" << endl;

Example run
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+
# 1
adding: United States (HEAD)
adding: Canada (prev: United States)
adding: Brazil (prev: Canada)
adding: India (prev: Brazil)
adding: China (prev: India)
adding: Australia (prev: China)
== CURRENT PATH ==
United States - Canada - Brazil - India - China - Australia - NULL
===
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+
# 3
Enter name of the country to receive the message:
Brazil
Enter the message to send:

bom dia
United States [# messages received: 1] received: bom dia
Canada [# messages received: 1] received: bom dia
Brazil [# messages received: 1] received: bom dia
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+
# 3
Enter name of the country to receive the message:
China
Enter the message to send:
ni hao
United States [# messages received: 2] received: ni hao
Canada [# messages received: 2] received: ni hao
Brazil [# messages received: 2] received: ni hao
India [# messages received: 1] received: ni hao
China [# messages received: 1] received: ni hao
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+

# 4
Enter a new country name:
Iran
Enter the previous country name (or First):
Canada
adding: Iran (prev: Canada)
== CURRENT PATH ==
United States - Canada - Iran - Brazil - India - China - Australia -
NULL
===
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+
# 5
Enter a country name:
Australia
== CURRENT PATH ==
United States - Canada - Iran - Brazil - India - China - NULL
===
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit

+-----------------------+
# 6
== CURRENT PATH ==
China - India - Brazil - Iran - Canada - United States - NULL
===
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+
# 7
deleting: China
deleting: India
deleting: Brazil
deleting: Iran
deleting: Canada
deleting: United States
Deleted network
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Delete Country
6. Reverse Network
7. Clear Network
8. Quit
+-----------------------+
# 8
Quitting... cleaning up path:
== CURRENT PATH ==

nothing in path
===
Path cleaned
Goodbye!