created description.md for Assignment3

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+Exercise 1. (25 points) Ford-Fulkerson
+We will implement the Ford-Fulkerson algorithm to calculate the Maximum Flow of a directed weighted graph. 
+Here, you will use the files WGraph.java and FordFulkerson.java,
+which are available on the course website. Your role will be to complete two methods in
+the template FordFulkerson.java.
+The file WGraph.java is similar to the file that you used in your previous assignment to
+build graphs. The only differences are the addition of setter and getter methods for the
+Edges and the addition of the parameters “source” and “destination”. There is also an
+additional constructor that will allow the creation of a graph cloning a WGraph object.
+Graphs are encoded using a similar format than the one used in the previous assignment.
+The only difference is that now the first line corresponds to two integers, separated by
+one space, that represent the “source” and the “destination” nodes. An example of such
+file can be found on the course website in the file ff2.txt. These files will be used
+as an input in the program FordFulkerson.java to initialize the graphs. This graph
+corresponds to the same graph depicted in [CLRS2009] page 727.
+Your task will be to complete the two static methods fordfulkerson(Integer source,
+Integer destination, WGraph graph, String filePath) and pathDFS(Integer source,
+Integer destination, WGraph graph). The second method pathDFS finds a path
+via Depth First Search (DFS) between the nodes “source” and “destination” in the
+“graph”. You must return an ArrayList of Integers with the list of unique nodes belonging to the path found by the DFS. 
+The first element in the list must correspond to
+the “source” node, the second element in the list must be the second node in the path,
+and so on until the last element (i.e., the “destination” node) is stored. The method
+fordfulkerson must compute an integer corresponding to the max flow of the “graph”,
+as well as the graph encoding the assignment associated with this max flow. The method
+fordfulkerson has a variable called myMcGillID, which must be initialized with your
+McGill ID number.
+Once completed, compile all the java files and run the command line java FordFulkerson
+ff2.txt. Your program must use the function writeAnswer to save your output in a file.
+An example of the expected output file is available in the file ff226000000.txt. This
+output keeps the same format than the file used to build the graph; the only difference
+is that the first line now represents the maximum flow (instead of the “source” and “destination” nodes). 
+The other lines represent the same graph with the weights updated
+to the values that allow the maximum flow. The file ff226000000.txt represents the
+answer to the example showed in [CLRS2009] Page 727. You are invited to run other
+examples of your own to verify that your program is correct.
+
+Exercise 2. (25 points) Bellman-Ford
+We want to implement the Bellman-Ford algorithm for finding the shortest path in
+a graph where edges can have negative weights. Once again, you will use the object
+WGraph. Your task is to complete the method BellmanFord(WGraph g, int source)
+and shortestPath(int destination) in the file BellmanFord.java.
+The method BellmanFord takes an object WGraph named g as an input and an integer
+that indicates the source of the paths. If the input graph g contains a negative cycle,
+then the method should throw an exception (see template). Otherwise, it will return
+an object BellmanFord that contains the shortest path estimates (the private array of
+integers distances), and for each node, its predecessor in the shortest path from the
+source (the private array of integers predecessors).
+The method shortestPath will return the list of nodes as an array of integers along
+the shortest path from the source to the destination. If this path does not exists, the
+method should throw an exception (see template).
+Input graphs are available on the course webpage to test your program. Nonetheless, we
+invite you to also make your own graphs to test your program.