Laboratory Exercises, C++ Programming

20 Tools for Practical C++ Development
4.2 Graph Representation
The first task is to choose a representation of the dependency graph. We will use a representation
where each vertex has a list of its neighbors. This list is called an adjacency list.
Consider the following makefile:
D: A
E: B D
B: A C
The dependencies in the makefile form the following graph (the graph to the left, the vertices
with their adjacency lists to the right):
A D
B
C E
A graph has a list of Vertex objects (A, B, C, D, E, in the figure). A vertex is represented by an object
of class Vertex, which has the attributes name (the label on the vertex) and adj (the adjacency
list). In the figure, the adjacency list of vertex A contains B and D.
The class definitions follow. First, class Vertex (the attribute color is used when traversing
the graph, see section 4.3):
class Vertex {
friend class VertexList; // give VertexList access to private members
private:
/* create a vertex with name nm */
Vertex(const std::string& nm);
};
std::string name; // name of the vertex
VertexList adj; // list of adjacent vertices
enum Color { WHITE, GRAY, BLACK };
Color color; // used in the traversal algorithm
In class VertexList, the adjacency list is implemented as a vector of pointers to other vertices
(vptrs). The functions top sort and dfs visit are described in section 4.3.
struct cyclic {}; // exception type, the graph is cyclic
class VertexList {
public:
/* create an empty vertex list, destroy the list */
VertexList();
~VertexList();
/* insert a vertex with the label name in the list */
void add_vertex(const std::string& name);
A
B
C
D
E