Question

writing this program in C, how else do i declare the struct Graph* graph = new Graph

and

graph->edge = new edge[E]

without using new because this is C

Answer 1

First, you need to know that C is procedure oriented,not object oriented like C++, so C doesn't require any object creation since it doesn't have any class. If you wish to create any structure object, kindly follow the following example-

#include<stdio.h>
struct data
{
int age;
char name[10];
}; //This is how a structure is defined
int main()
{
struct data s1,s2; //This is how objects of structure is created(two objects created).
s1.age=14;
s2.age=13;
scanf("%s%s",s1.name,s2.name); //Here I have taken input from user in this way, for the names of two objects for which the structure was created
printf("%s %s %d %d",s1.name,s2.name,s1.age,s2.age);
return 0;
}

The above program might give you a idea of how to define or create structure objects. Now back to your query,

just define the graph structure and then in main function, use struct graph g; which will create an object for your graph structure.For the edge if you are creating any nested structure, then you will have to call it like-

struct graph g;

struct g.edge e;

//Below is an example of nested structure and how to create objects of nested structure

struct student

{

    struct person

    {

        char name[20];

        int age;

        char dob[10];

    } p ;

    int rollno;

    float marks;

} stu;

stu.p.age will help you access the age of person structure inside student structure.

I hope that I could help you understand the concept of using structures in C. If you need more help, there are other online video tutorials available in youtube.