The adjacency list representation of a graph stores adjacencies,
not in a 2-dimensional boolean matrix, but in an array of linked lists.
Suppose that the vertex Boston has three neighbors,
Chicago, Cleveland, and Baltimore.
Further suppose that Boston appears in slot 5 in the
String array names.
Then slot 5 in Edges would contain a linked list
with Chicago, Cleveland, and Baltimore,
in some order.
Implement a new myGraph class that uses the adjacency list
representation rather than the adjacency matrix representation.
The only public methods you are required to implement are
the the two constructors, addVertex, and addEdge.
Notice that the linked list mentioned above contains strings.
This means that the Link class and the
LinkList class have to be modified