The Arc and Digraph classes

1. Design and implement an Arc class to go with the Vertex class above. In practice, an Arc object just needs to know its starting and ending vertex IDs.
2. Design and implement a Digraph class to go with the Vertex and Arc classes defined above. This needs to store a TimeStamp object, a vector of pointers to Vertex objects, a vector of pointers to Arc objects. We need methods both for constructing (addVertex, addArc) as well as accessing the graph information (getNumberOfVertices, getNumberOfArcs, getVertex, getArc). We also want to be able to send a Digraph object to the cout stream to have a GraphViz compatible text output which we shall display using the GraphViz utilities.

Test your implementation on the following program dgdriver.cxx:

#include<iostream>
#include "digraph.h"

int main(int argc, char** argv) {
  using namespace std;
  string urlName1 = "name1";
  string urlName2 = "name2";
  string urlName3 = "name3";
  URL* urlPtr1 = new URL(urlName1);
  URL* urlPtr2 = new URL(urlName2);
  URL* urlPtr3 = new URL(urlName3);
  VertexURL* vtxURLPtr1 = new VertexURL(1, urlPtr1);
  VertexURL* vtxURLPtr2 = new VertexURL(2, urlPtr2);
  VertexURL* vtxURLPtr3 = new VertexURL(3, urlPtr3);
  Vertex* vtxPtr1 = vtxURLPtr1;
  Vertex* vtxPtr2 = vtxURLPtr2;
  Vertex* vtxPtr3 = vtxURLPtr3;
  vtxPtr1->addAdjacentVertexID(2);
  vtxPtr1->addAdjacentVertexID(3);
  vtxPtr2->addAdjacentVertexID(1);
  vtxPtr3->addAdjacentVertexID(3);
  Arc* arcPtr1 = new Arc(1,2);
  Arc* arcPtr2 = new Arc(1,3);
  Arc* arcPtr3 = new Arc(2,1);
  Arc* arcPtr4 = new Arc(3,3);
  TimeStamp t;
  t.update();
  Digraph G;
  G.setTimeStamp(t);
  G.addVertex(*vtxPtr1);
  G.addVertex(*vtxPtr2);
  G.addVertex(*vtxPtr3);
  G.addArc(*arcPtr1);
  G.addArc(*arcPtr2);
  G.addArc(*arcPtr3);
  G.addArc(*arcPtr4);
  cout << G;
  return 0;
}

and verify that the output is:

# graphviz output by WET (L. Liberti 2006)
digraph www_1158015497 {
  0 [ label = "name1" ];
  1 [ label = "name2" ];
  2 [ label = "name3" ];
  3 [ label = "Thu Jan 10 19:24:53 2008", color = red ];
   1 -> 2;
   1 -> 3;
   2 -> 1;
   3 -> 3;
}