I can only edit two files AdjacencyListGraph.h and AdjacencyMatrixGraph. Below I have added those two files

#ifndef ADJACENCYLISTGRAPH$\_$H

#define ADJACENCYLISTGRAPH$\_$H

#include "DirectedGraph.h$"$

#include "AdjacencyListVertex.h$"$

class AdjacencyListGraph : public DirectedGraph $\{$

protected:

std::vector vertices;

public:

virtual ~AdjacencyListGraph$()\{$

for $($AdjacencyListVertex$*$ vertex : vertices$)\{$

delete vertex;

$\}$

$\}$

$//$ Creates and adds a new vertex to the graph, provided a vertex with the

$//$ same label doesn't already exist in the graph. Returns the new vertex on

$//$ success, nullptr on failure.

virtual Vertex$*$ AddVertex$($std::string newVertexLabel$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return nullptr;

$\}$

$//$ Adds a directed edge from the first to the second vertex. If the edge

$//$ already exists in the graph, no change is made and false is returned.

$//$ Otherwise the new edge is added and true is returned.

virtual bool AddDirectedEdge$($Vertex$*$ fromVertex, Vertex$*$ toVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return false;

$\}$

$//$ Returns a vector of edges with the specified fromVertex.

virtual std::vector GetEdgesFrom$($Vertex$*$ fromVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return std::vector$()$;

$\}$

$//$ Returns a vector of edges with the specified toVertex.

virtual std::vector GetEdgesTo$($Vertex$*$ toVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return std::vector$()$;

$\}$

$//$ Returns a vertex with a matching label, or nullptr if no such vertex

$//$ exists

virtual Vertex$*$ GetVertex$($std::string vertexLabel$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return nullptr;

$\}$

$//$ Returns true if this graph has an edge from fromVertex to toVertex

virtual bool HasEdge$($Vertex$*$ fromVertex, Vertex$*$ toVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return false;

$\}$

$\}$;

#endif

#ifndef ADJACENCYMATRIXGRAPH$\_$H

#define ADJACENCYMATRIXGRAPH$\_$H

#include "DirectedGraph.h$"$

class AdjacencyMatrixGraph : public DirectedGraph $\{$

protected:

std::vector vertices;

$//$ If matrixRows$[$X$][$Y$]$ is true, then an edge exists from vertices$[$X$]$ to

$//$ vertices$[$Y$]$

std::vector$>$ matrixRows;

$//$ TODO: Type your additional code here, if desired

public:

virtual ~AdjacencyMatrixGraph$()\{$

for $($Vertex$*$ vertex : vertices$)\{$

delete vertex;

$\}$

$\}$

$//$ Creates and adds a new vertex to the graph, provided a vertex with the

$//$ same label doesn't already exist in the graph. Returns the new vertex on

$//$ success, nullptr on failure.

virtual Vertex$*$ AddVertex$($std::string newVertexLabel$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return nullptr;

$\}$

$//$ Adds a directed edge from the first to the second vertex. If the edge

$//$ already exists in the graph, no change is made and false is returned.

$//$ Otherwise the new edge is added and true is returned.

virtual bool AddDirectedEdge$($Vertex$*$ fromVertex, Vertex$*$ toVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return false;

$\}$

$//$ Returns a vector of edges with the specified fromVertex.

virtual std::vector GetEdgesFrom$($Vertex$*$ fromVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return std::vector$()$;

$\}$

$//$ Returns a vector of edges with the specified toVertex.

virtual std::vector GetEdgesTo$($Vertex$*$ toVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return std::vector$()$;

$\}$

$//$ Returns a vertex with a matching label, or nullptr if no such vertex

$//$ exists

virtual Vertex$*$ GetVertex$($std::string vertexLabel$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return nullptr;

$\}$

$//$ Returns true if this graph has an edge from fromVertex to toVertex

virtual bool HasEdge$($Vertex$*$ fromVertex, Vertex$*$ toVertex$)$ override $\{$

$//$ TODO: Type your code here $($remove placeholder line below$)$

return false;

$\}$

$\}$;

#endif