I need to know why I get an access violation error and if possible, how to fix i

Question

I need to know why I get an access violation error and if possible, how to fix it. Here is my code:

#include <iostream>
using namespace std;

struct Edge
{
   int vertex1;
   int vertex2;
};

int adjMat[4][4];
void insertEdge( Edge e, int adjMat[4][4]);
void printGraph (int adjMat[4][4]);

struct Node
{
int Vertex;
Node* next;
};

void printList(Node* adjList[4][4]);

int main()
{
   Edge one; Edge two; Edge three; Edge four; Edge five; Edge six;
   one.vertex1 = 0;
   one.vertex2 = 1;
   two.vertex1 = 0;
   two.vertex2 = 3;
   three.vertex1 = 1;
   three.vertex2 = 0;
   four.vertex1 =1;
   four.vertex2 =2;
   five.vertex1 = 2;
   five.vertex2 = 1;
   six.vertex1 = 3;
   six.vertex2 = 0;
   insertEdge(one, adjMat);
   insertEdge(two, adjMat);
   insertEdge(three, adjMat);
   insertEdge(four, adjMat);
   insertEdge(five, adjMat);
   insertEdge(six, adjMat);
   cout<<"Adjacency Matrix ";
   cout<<" 1 2 3 4 ";
   printGraph(adjMat);
   cout << "Adjacency List: ";
   Node* adjList[4][4];
   adjList[4][4] = new Node;
   adjList[0][0] = new Node;
   adjList[0][1] = new Node;
   adjList[0][2] = new Node;
   adjList[0][3] = new Node;
   adjList[1][0] = new Node;
   adjList[1][1] = new Node;
   adjList[1][2] = new Node;
   adjList[1][3] = new Node;
   adjList[2][0] = new Node;
   adjList[2][1] = new Node;
   adjList[2][2] = new Node;
   adjList[2][3] = new Node;
   adjList[3][0] = new Node;
   adjList[3][1] = new Node;
   adjList[3][2] = new Node;
   adjList[3][3] = new Node;
   /*adjList[0][1]->Vertex = 1;
   adjList[0][3]->Vertex = 1;
   adjList[1][0]->Vertex = 2;
   adjList[1][2]->Vertex = 2;
   adjList[2][1]->Vertex = 3;
   adjList[3][0]->Vertex = 4;*/
   adjList[0][0] -> Vertex = NULL;
   adjList[0][1] -> Vertex = 1;
   adjList[0][2] -> Vertex = NULL;
   adjList[0][3] -> Vertex = 1;
   adjList[0][0] -> next = adjList[0][1];
   adjList[0][0] -> next = NULL;
   adjList[0][1] -> next = adjList[0][2];
   adjList[0][1] -> next -> Vertex = 2;
   adjList[0][2] -> next = adjList[0][3];
   adjList[0][2] -> next = NULL;
   adjList[0][3] -> next -> Vertex = 4;
   adjList[1][0] -> Vertex = 2;
   adjList[1][1] -> Vertex = NULL;
   adjList[1][2] -> Vertex = 3;
   adjList[1][3] -> Vertex = NULL;
   adjList[1][0] -> next = adjList[1][1];
   adjList[1][0] -> next -> Vertex = 3;
   adjList[1][1] -> next = adjList[1][2];
   adjList[1][1] -> next -> Vertex = 3;
   adjList[1][2] -> next = adjList[1][3];
   adjList[1][2] -> next -> Vertex = 2;
   adjList[1][3] -> next = NULL;
   adjList[2][0] -> Vertex = NULL;
   adjList[2][1] -> Vertex = 3;
   adjList[2][2] -> Vertex = NULL;
   adjList[2][3] -> Vertex = NULL;
   adjList[2][0] -> next = adjList[2][1];
   adjList[2][0] -> next -> Vertex = 2;
   adjList[2][1] -> next = adjList[2][2];
   adjList[2][1] -> next -> Vertex = 2;
   adjList[2][2] -> next = NULL;
   adjList[2][3] -> next = NULL;
   adjList[3][1] -> Vertex = NULL;
   adjList[3][2] -> Vertex = NULL;
   adjList[3][3] -> Vertex = NULL;
   adjList[3][0] -> next = adjList[3][1];
   adjList[3][0] -> next -> Vertex = 1;
   adjList[3][1] -> next = adjList[3][2];
   adjList[3][1] -> next -> Vertex = NULL;
   adjList[3][2] -> next = NULL;
   adjList[3][3] -> next = NULL;
   printList(adjList);
system("pause");
}

void insertEdge(Edge e, int adjMat[4][4])
{
   int a;
   int b;
   a = e.vertex1;
   b = e.vertex2;
   adjMat[a][b] = 1;
}

void printGraph(int adjMat[4][4])
{
   int x = 0;
   int y = 0;
   while (x < 4)
   {
       cout << x + 1 << " [" << adjMat[x][y] << "] ";
       while (y < 3)
       {
           y++;
           cout << " [" << adjMat[x][y] << "] ";
       }
   x++;
   y = 0;
   cout << endl;
   }
}

void printList(Node* adjList[4][4])
{
   int a;
   for(int b = 0; b < 3; b++)
   {
       a = 0;
       do
       {
           cout << "(" << adjList[b][a] -> Vertex;
           cout << ", " << adjList[b][a] -> next -> Vertex << ") ";
           a++;
       }
       while(adjList[b][a] -> next != NULL);
   }
   cout << endl << endl;
}

Explanation / Answer

#include using namespace std; struct Edge { int vertex1; int vertex2; }; int adjMat[4][4]; void insertEdge( Edge e, int adjMat[4][4]); void printGraph (int adjMat[4][4]); struct Node { int Vertex; Node* next; }; void printList(Node* adjList[4][4]); int main() { Edge one; Edge two; Edge three; Edge four; Edge five; Edge six; one.vertex1 = 0; one.vertex2 = 1; two.vertex1 = 0; two.vertex2 = 3; three.vertex1 = 1; three.vertex2 = 0; four.vertex1 =1; four.vertex2 =2; five.vertex1 = 2; five.vertex2 = 1; six.vertex1 = 3; six.vertex2 = 0; insertEdge(one, adjMat); insertEdge(two, adjMat); insertEdge(three, adjMat); insertEdge(four, adjMat); insertEdge(five, adjMat); insertEdge(six, adjMat); coutVertex = 3; adjList[3][0]->Vertex = 4;*/ adjList[0][0] -> Vertex = NULL; adjList[0][1] -> Vertex = 1; adjList[0][2] -> Vertex = NULL; adjList[0][3] -> Vertex = 1; adjList[0][0] -> next = adjList[0][1]; adjList[0][0] -> next = NULL; adjList[0][1] -> next = adjList[0][2]; adjList[0][1] -> next -> Vertex = 2; adjList[0][2] -> next = adjList[0][3]; adjList[0][2] -> next = NULL; adjList[0][3]->next=adjList[0][2]; adjList[0][3] -> next -> Vertex = 4; //Here adjlist[0][3]->next was null and you were trying to access vertex of it adjList[1][0] -> Vertex = 2; adjList[1][1] -> Vertex = NULL; adjList[1][2] -> Vertex = 3; adjList[1][3] -> Vertex = NULL; adjList[1][0] -> next = adjList[1][1]; adjList[1][0] -> next -> Vertex = 3; adjList[1][1] -> next = adjList[1][2]; adjList[1][1] -> next -> Vertex = 3; adjList[1][2] -> next = adjList[1][3]; adjList[1][2] -> next -> Vertex = 2; adjList[1][3] -> next = NULL; adjList[2][0] -> Vertex = NULL; adjList[2][1] -> Vertex = 3; adjList[2][2] -> Vertex = NULL; adjList[2][3] -> Vertex = NULL; adjList[2][0] -> next = adjList[2][1]; adjList[2][0] -> next -> Vertex = 2; adjList[2][1] -> next = adjList[2][2]; adjList[2][1] -> next -> Vertex = 2; adjList[2][2] -> next = NULL; adjList[2][3] -> next = NULL; adjList[3][1] -> Vertex = NULL; adjList[3][2] -> Vertex = NULL; adjList[3][3] -> Vertex = NULL; adjList[3][0] -> next = adjList[3][1]; adjList[3][0] -> next -> Vertex = 1; adjList[3][1] -> next = adjList[3][2]; adjList[3][1] -> next -> Vertex = NULL; adjList[3][2] -> next = NULL; adjList[3][3] -> next = NULL; printList(adjList); system("pause"); } void insertEdge(Edge e, int adjMat[4][4]) { int a; int b; a = e.vertex1; b = e.vertex2; adjMat[a][b] = 1; } void printGraph(int adjMat[4][4]) { int x = 0; int y = 0; while (x < 4) { cout

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