AdjacencyMatrixAllOperation

#include<stdio.h>
#include<stdlib.h>
#define MAX 20

int graph_type,n,max_edges,i,j,origin,destination;
int adj[MAX][MAX];
void create_graph();
void display();
void insert_edge(int, int);
void delete_edge(int, int);

int main()
{   int choice;
    create_graph();
    while(1)
    {   printf("1.Insert an edge: \n");
        printf("2.Delete an edge: \n");
        printf("3.Display: \n");
        printf("4.Exit: \n");
        printf("Enter your choice:  ");
        scanf("%d", & choice);
        switch(choice)
            {   case 1: printf("Enter an edge to be inserted:  ");
                        scanf("%d %d",&origin,&destination);
                        insert_edge(origin,destination);
                        break;
                case 2: printf("Enter an edge to be deleted:  ");
                        scanf("%d %d",&origin,&destination);
                        delete_edge(origin,destination);
                        break;
                case 3: display();
                        break;
                case 4: exit(1);
                default:printf("Wrong choice \n");
                        break;
            }//switch
    }//while
    return 0;
}//main

void create_graph()
{
    printf("Enter Graph type '1' for undirected and '2' for directed graph:  ");
    scanf("%d",&graph_type);
    printf("Enter number of vertices:  ");
    scanf("%d",&n);
    if (graph_type == 1)
        max_edges = n*(n-1)/2;
    else
        max_edges = n*(n-1);

    for(i=0;i<=max_edges;i++)
    {   printf("Enter edges (origin & destination), Enter -1 -1 to exit:  ");
        //enter value as 'int' space 'int' because here is '%d' space '%d'
        scanf("%d %d",&origin,&destination);
        if(origin == -1 && destination == -1)
            break;
        if(origin>=n || destination >= n || origin < 0 || destination < 0)//checking for limitations
        {   printf("Invalid data please enter again: \n");
            i--;
        }
        else
            adj[origin][destination] = 1;
        if(graph_type == 1) // since for undirected graph origin & destination are exchangable
            adj[destination][origin] =1;
    }
}//end of create_graph

void display()
{   printf("\nThe adjacent matrix is following:  \n\n");
    for(i=0;i<n;i++)
    {
            for(j=0;j<n;j++)
            printf("%4d",adj[i][j]);
            printf("\n");
        }
}//end of display

void insert_edge(int origin, int destination)
{   if(origin < 0 || origin >= n)
    {   printf("Origin does not exist:  \n");
        return;
    }
    if(destination < 0 || destination >= n)
    {   printf("Destination does not exist:  \n");
        return;
    }
    adj[origin][destination] = 1;
    if (graph_type == 1)
        adj[destination][origin] =1;
}//end of insert_edge

void delete_edge(int origin, int destination)
{   if(origin < 0 || origin >= n || destination < 0 || destination >= n || adj[origin][destination]==0)
    {   printf("This edge does not exist: \n");
        return;
    }
    adj[origin][destination] = 0;
    if (graph_type == 1)
    adj[destination][origin] =0;
}//end of delete_edge