CSC349-Project 5: Directed Graphs Solved

Define a class DiGraph to implement a directed graph as an array of Adjacency Linked Lists. Vertices are numbered by integers 0 through N-1 (N is the number of vertices in the graph). DiGraph class contains one private instance variable, one constructor and 5 public methods:One private instance variable: this is an array of linked lists (use Java’s LinkedList class).
A constructor with one int type parameter for N. This constructor creates and initializes the instance variable-array.
A public method addEdge(int from, int to) where two parameters identify vertices representing the edge that needs to be added to the graph (to vertex is added as from vertex’s neighbor).
Important: the edge should not be added if it already exists: needs to be checked before adding.

Attention: vertex-numbers are given in natural numbering (starting with 1) so you should “turn” them to Java-indexing to reflect correct connection. No need for validity check.

A public method deleteEdge(int from, int to) where two parameters identify vertices representing the edge that needs to be deleted from the graph (to vertex is removed as from vertex’s neighbor). Note: nothing is done if such edge doesn’t exist (no error message or exception).
Attention: vertex-numbers are given in natural numbering (starting with 1) so you should “turn” them to Java-indexing to reflect correct connection. No need for validity check.

A public method edgeCount(): computes and returns the number of edges in the graph.
A public method vertexCount(): returns the number of vertices in the graph (it’s the array’s length)
A public method print() that outputs the graph in the following format: for each vertex i (from 0 to N-1) outputs a line: i is connected to: x1, …,  xk  where x1,…, xk are vertices that are adjacent to i.        Example: for some 5-vertex graph your output may look like this:
                   1 is connected to: 2,  4                    2 is connected to: 

is connected to: 2, 4,  1 
is connected to: 3 
is connected to: 3, 1 
 

Attention: numbering of vertices in the output should be natural, i.e. starting with 1.

 Important: Separate two neighbors with a comma; do NOT put comma after the last neighbor

Define an application class  In main method of this class you need to do the following:
Define a scanner object for keyboard input (i.e. connect it to in). You must make a scanner for System.in only once here and use it for all keyboard inputs in this main method. DON’T redefine this scanner or create a new scanner for System.in – it will cause problems in grading.
Prompt the user to enter the number of vertices.
Input the number of vertices and define an object of DiGraph
Output a menu to the user, listing the above mentioned 5 operations that your DiGraph class provides. For example, your menu may look like this:
Choose one of the following operations: 

add edge (enter a) 
delete edge (enter d) 
edge count (enter e) 
vertex count (enter v) 
print graph (enter p) - Quit (enter q) 
Important: must use a, d, e, v, p, q letters for menu choices (do NOT change these letters) 

For as long as the user does not choose to quit, do the following:
Prompt the user to enter a menu choice (do NOT print the menu here; the menu should be output only once, in step 3 above, before entering this loop).
Input user’s choice and analyze it (you are recommended to use a switch statement with default case which will be executed for invalid menu choices). Arrange the execution of the requested operation; if input values are necessary (for add edge and delete edge menu choices), prompt the user to enter two integers and input them (no need for validity check). For every request, after executing it, output feedback: e.g. if you are adding/deleting an edge, output a message saying for example that the edge (x, y) was added/deleted; if you are giving some returned answer (e.g.
number of edges), precede it with an informative message (e.g. “Number of edges is: ”); or before printing the graph, output a sentence “The graph is the following:”

Note: in all communications with the user the vertex numbering is natural, i.e. starting with 1.

Edit, compile and execute DiGraphTest class, test it thoroughly. When running the program, first provide the graph by inputting N (number of vertices) and then one by one adding vertices (with ‘a’ menu option). Extensively test the functionality of your program: request different menu choices and check their execution; then add and delete edges to change the graph and repeat the testing for the modified graph. Finish testing when you are absolutely sure all the functionality of the program is correct.
 

 

Part 2 of 4 (15 points):  

 

 Make additions in the DiGraph class to include the implementation of the Topological Sort algorithm including a supporting routine for computing vertex indegrees.
 

Add the following content to the DiGraph class’s definition.  

A private method indegrees: returns an array of integers representing the indegrees of all vertices in the graph: the i-th integer in the resulting array is the indegree of the i-th vertex.
A public method topSort: returns an array containing the list of topologically sorted vertices (values in the array should represent natural vertex-numbers, i.e. starting with 1).
Important: If the graph is cyclic, this method must throw IllegalArgumentException type exception (read the note on top of the last page of your Topological Sort lecture handout). 

 

Attention: In topSort you need a regular queue and NOT a priority queue. To implement a queue in Java, you can simply use an object of LinkedList class (for integers). Your list will function like a regular queue if you always add an element to the end using addLast method, and delete an element from the front using removeFirst method.

     

Make additions to the DiGraphTest class’s main method to incorporate one additional service. 
 

Add one new menu-choice for outputting the topologically sorted list of vertices of the graph and arrange the execution of that new service.

 

 

Attention: 1. Use t letter for the new menu choice (t - topological sort).

Numbering of vertices in the output should be natural (starts with 1).
The list should be output on one line, with vertex-numbers separated by commas. Important: there should NOT be a comma after the last vertex.
 

Edit, compile and execute DiGraphTest program, testing the new service very thoroughly.
 

DEMO: Under Project5 on Canvas there is a link to demo instructions. Run your program according to these instructions, make sure all answers/outputs are correct, and then put a request for me to come to your breakout room. I will visit you to check your work.