Word Chaining

#include "VertexChain.cpp"
#include <string>
#include <iostream>
using namespace std;
class graph {
  public:
	vector<VertexChain*> g;
	// Challenge function
	bool CanChainWords(int list_size) // Receiving the size of list from main 
	{
        // TODO: Write - Your - Code
		return false;
	}
	// This method creates a graph from a list of words. A node of
	// the graph contains a character representing the start or end
	// character of a word.
	void CreateGraph(vector<string> words_list) {
		for (int i = 0; i < words_list.size(); i++) {
			string word = words_list[i];
			char start_char = word[0];
			char end_char = word[word.length() - 1];
			VertexChain* start = VertexChainExists(start_char);
			if (start == nullptr) {
				start = new VertexChain(start_char, false);
				g.push_back(start);
			}
			VertexChain* end = VertexChainExists(end_char);
			if (end == nullptr) {
				end = new VertexChain(end_char, false);
				g.push_back(end);
			}
			// Add an edge from start vertex to end vertex
			AddEdge(start, end);
		}
	}
	// This method returns the VertexChain with a given value if it
	// already exists in the graph, returns NULL otherwise
	VertexChain* VertexChainExists(char value) {
		for (int i = 0; i < this->g.size(); i++) {
			if (g[i]->value == value) {
				return g[i];
			}
		}
		return nullptr;
	}
	// This method returns TRUE if all nodes of the graph have
	// been visited
	bool AllVisited() {
		for (int i = 0; i < g.size(); i++) {
			if (g[i]->visited == false) {
				return false;
			}
		}
		return true;
	}
	// This method adds an edge from start VertexChain to end VertexChain by
	// adding the end VertexChain in the adjacency list of start VertexChain
	// It also adds the start VertexChain to the in_vertices of end VertexChain
	void AddEdge(VertexChain* start, VertexChain* end) {
		start->adj_vertices.push_back(end);
		end->in_vertices.push_back(start);
	}
	// This method returns TRUE if out degree of each vertex is equal
	// to its in degree, returns FALSE otherwise
	bool OutEqualsIn() {
		for (int i = 0; i < g.size(); i++) {
			int out = g[i]->adj_vertices.size();
			int inn = g[i]->in_vertices.size();
			if (out != inn) {
				return false;
			}
		}
		return true;
	}
	void PrintGraph() {
		for (int i = 0; i < g.size(); i++) {
			cout << g[i] << ' ' << g[i]->visited << endl;
			vector<VertexChain*> adj = g[i]->adj_vertices;
			for (int j = 0; j < adj.size(); j++) {
				cout << adj[j] << ' ';
			}
			cout << endl;
		}
	}
};