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Assignment 3 - Linked Lists
OBJECTIVES
1. Create, traverse, add nodes to 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.cppand the driver file main.cpp.
The linked-list itself will be implemented using the following struct (already included in the header file):
struct Country
{
// name of the country
string name;
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 CountryNetworkclass definition is provided in the file CountryNetwork.hppin 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
void insertCountry(Country* previous, string countryName); // Beware of edge cases
• Insert a new country with name countryNamein the linked list after the country pointed to by previous. If previousis 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 loadDefaultSetup();
• 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 transmitMsg(stringreceiver, 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 messageto msgand increment the node’s numberMessagesfield. If the list is empty, print "Empty list" and exit the function. If the node is not present, print “Country not found”.
• 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 displayMenufunction 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 loadDefaultSetupfunction, 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 printPathfunction. 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 getlinein case there are spaces in the user input). Pass the message and country name to the transmitMsgfunction. Don’t forget to add a newline after the message is collected, and before the output is printed. This is done for better readability.
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”:
Example 1:
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:
Example 2:
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
If the user then decides to transmit the message “Sushi” to “Japan”, the output when the country is not present will be:
Example 3:
Enter name of the country to receive the message:
Japan
Enter the message to send:
Sushi
Country not found
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 searchNetworkand insertCountryto 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(previous country name)...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 printPathto demonstrate the new linked-list.
• First letter of the country to be added should be Uppercase (sentence case) e.g. If you want to add “mexico, it should be stored as “Mexico” in 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: Quit
Print the following message:
cout << "Quitting..." << 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. Quit
+-----------------------+
#> 2
== CURRENT PATH ==
nothing in path
===
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Quit
+-----------------------+
#> 3
Enter name of the country to receive the message:
Japan
Enter the message to send:
Cherry Blossom
Empty list
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Quit
+-----------------------+
#> 1
adding: prev: [HEAD]
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. Quit
+-----------------------+
#> 2
== 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. Quit
+-----------------------+
#> 3
Enter name of the country to receive the message:
Japan
Enter the message to send:
Sushi
Country not found
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Quit
+-----------------------+
#> 4
Enter a new country name:
Japan
Enter the previous country name (or First):
United States
adding: Japan (prev: United States)
== CURRENT PATH ==
United States -> Japan -> 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. Quit
+-----------------------+
#> 3
Enter name of the country to receive the message:
Australia
Enter the message to send:
Kangaroo
United States [# messages received: 1] received: Kangaroo
Japan [# messages received: 1] received: Kangaroo
Canada [# messages received: 1] received: Kangaroo
Brazil [# messages received: 1] received: Kangaroo
India [# messages received: 1] received: Kangaroo
China [# messages received: 1] received: Kangaroo
Australia [# messages received: 1] received: Kangaroo
Select a numerical option:
+=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Quit
+-----------------------+
#> 3
Enter name of the country to receive the message:
Brazil
Enter the message to send:
Football
United States [# messages received: 2] received: Football
Japan [# messages received: 2] received: Football
Canada [# messages received: 2] received: Football Brazil [# messages received: 2] received: Football Select a numerical option: +=====Main Menu=========+
1. Build Network
2. Print Network Path
3. Transmit Message
4. Add Country
5. Quit
+-----------------------+
#> 4
Enter a new country name:
Singapore
Enter the previous country name (or First):
First
adding: Singapore (HEAD)
== CURRENT PATH ==
Singapore -> United States -> Japan -> 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. Quit
+-----------------------+
#> 4
Enter a new country name:
Australia
Enter the previous country name (or First):
Spain
INVALID(previous country name)...Please enter a VALID previous country
name!
Canada
adding: Australia (prev: Canada)
== CURRENT PATH ==
Singapore -> United States -> Japan -> Canada -> Australia -> 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. Quit
+-----------------------+
#> 5
Quitting... cleaning up path:
== CURRENT PATH ==
Singapore -> United States -> Japan -> Canada -> Australia -> Brazil ->
India -> China -> Australia -> NULL
===
Goodbye!
Appendix:
1) CountryNetwork::insertCountry()
a) cout << "adding: " << countryName << " (HEAD)" << endl;
b) cout << "adding: " << countryName << " (prev: " << previous->name << ")" << endl;
2) CountryNetwork::transmitMsg()
a) cout << "Empty list" << endl;
b) cout << "Country not found" << endl;
c) cout << sender->name << “ [# messages received: " <<
sender->numberMessages << "] received: " << sender->message << endl;
3) CountryNetwork::printPath()
a) cout << "== CURRENT PATH ==" << endl;
b) cout << "nothing in path" << endl;
c) cout << ptr->name << " -> ";
d) cout << ptr->name << " -> ";
e) cout << "NULL" << endl;
f) cout << "===" << endl;
4) main()
a) cout << "Enter name of the country to receive the message: "<< endl;
b) cout << "Enter the message to send: " << endl;
c) cout << endl;
d) cout << "Enter a new country name: " << endl;
e) cout << "Enter the previous country name (or First): " << endl;
f) cout << "INVALID(previous country name)...Please enter a VALID previous country name!" << endl;
g) cout << "Quitting..." << endl;
h) cout << "Invalid Input" << endl;
i) cout << "Goodbye!" << endl;
5) displayMenu()
a) cout << endl;
b) cout << "Select a numerical option:" << endl;
c) cout << "+=====Main Menu=========+" << endl;
d) cout << " 1. Build Network " << endl;
e) cout << " 2. Print Network Path " << endl;
f) cout << " 3. Transmit Message " << endl;
g) cout << " 4. Add Country " << endl;
h) cout << " 5. Quit " << endl;
i) cout << "+-----------------------+" << endl;
j) cout << "#> ";
