The function that I am having a problem with is in the middle of this seperated from the rest of the code.

#ifndef GRAPH_H

#define GRAPH_H

#include <string>
#include "queue.h"
using namespace std;


class FileOpenError                                 // Exception class -- cannot open input file
{
};

struct EdgeNode										// Structure representing an edge
{
  int			destination;						// Index of destination vertex
  int			weight;								// Edge weight
  EdgeNode*		nextPtr;							// Next edge pointer
};

struct VertexNode									// Structure representing a vertex
{
  string		vname;								// Name of vertex
  bool			mark;								// Marked flag
  EdgeNode*		edgePtr;							// Pointer to list of edges
};


class Graph											// Graph ADT using adjacency list representation
{
 private:		//***** Private class members below *****//
  VertexNode*	vertices;							// Array of vertex nodes
  int			numV;								// Number of vertices

 public:		//***** Public members below *****//
  Graph(int num);									// Constructor - creates graph with num vertices
  ~Graph();											// Destructor - deallocates all edge nodes and the vertex list
  void DeleteAllEdges();							// Deallocates all edge nodes from all vertices
  bool IsEmpty();									// Returns true if graph empty, false otherwise
  bool IsFull();									// Returns true if graph full, false otherwise
  void AddVertex(string v);							// Adds vertex to graph assuming vertex not already present
  void AddEdge(string s, string d, int w);	        // Adds edge from source S  to destination D with specified weight W
  int IndexIs(string v);							// Returns index of edge from S to D; -1 if not present
  int WeightIs(string s, string d);					// Returns weight of vertex V -- assumes V is in graph
  void GetToVertices(string s, Queue& q);			// Returns a queue Q of vertices adjacent to vertex V
  void ClearMarks();								// Clears vertex marks
  void MarkVertex(string v);						// Marks vertex V
  bool IsMarked(string v);							// Returns true if vertex V is marked, false otherwise
  void Print();										// Write graph to stdout
  Queue* DepthFirstSearch(string startVertex, string endVertex);  // Returns ptr to queue containing path or NULL if none
}; 

  void Load(string filename, Graph*& g, string& startVertex, string& endVertex);  	
  // Load graph from named file and values of start and end vertices
  // Note: this file attempts to open the named file for input and input all information.  
  // If the file fails to open, Load throws the FileOpenError exception

#endif

using namespace std;

Graph::Graph(int num):vertices(NULL),numV(num)
{
	if (num) {
		vertices = new VertexNode[num];
	}
}

Graph::~Graph()
{
	delete [] vertices;
}

void Graph::DeleteAllEdges()
{
	VertexNode* temp = NULL;
}

bool Graph::IsEmpty()
{
	return(numV == 0);
}

bool Graph::IsFull()
{

}

void Graph::AddVertex(string v)
{
	for(int numNodes = 0; numNodes <= numV; numNodes++)
	{
		if (vertices[numNodes].vname.empty()) {
			vertices[numNodes].vname = v;
			vertices[numNodes].edgePtr = NULL;
			vertices[numNodes].mark = false;
			break;
		}
		//Graph::AddVertex(string v);
	}
}

void Graph::AddEdge(string s, string d, int w)
{
 	int sV = IndexIs(s);
	int dV = IndexIs(d);

            EdgeNode *edge = vertices[sV].edgePtr;
                vertices[sV].edgePtr = new EdgeNode;
				vertices[sV].edgePtr->nextPtr = edge;
				vertices[sV].edgePtr->weight = w;
                vertices[sV].edgePtr->destination = dV;

}

int Graph::IndexIs(string v)
{
	for(int numNodes = 0; numNodes <= numV; numNodes++)
	{
		if (vertices[numNodes].vname == v) {
			return numNodes;
		}
	}
	return -1;
}

int Graph::WeightIs(string s, string d)
{
	int sV = IndexIs(s);
	int dV = IndexIs(d);

    EdgeNode *edge = vertices[sV].edgePtr;
    while (edge) {
    	if (edge->destination == dV) {
			return edge->weight;
		}
		edge = edge->nextPtr;
	}
	return -1;
}

void Graph::GetToVertices(string s, Queue& q)
{
	int sV = IndexIs(s);

    EdgeNode *edge = vertices[sV].edgePtr;
    while (edge) {
		q.Enqueue(s);
		edge = edge->nextPtr;
	}
}

void Graph::ClearMarks()
{
}

The problem function
How do I mark the node as visited?

void Graph::MarkVertex(string v)
{
	bool marked = v;
}
bool Graph::IsMarked(string v)
{
}

void Graph::Print()
{
    
	for (int node = 0; node <+ numV; node++){
		cout << vertices[node].vname;
		if (!vertices[node].edgePtr){
		cout << endl;
			continue;
			
		}
		EdgeNode *edge = vertices[node].edgePtr;
        while (edge) {
			cout << vertices[edge->destination].vname << edge->weight;
			edge = edge->nextPtr;
		}
		cout << endl;
 }
	

}
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