adjacency list implementation in c

graph.c

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>

#define N    10

typedef struct {
    int y;
    int weight;
    struct Edge *next; /* next in adj list */
} Edge;

typedef struct {
    int x;
    struct Edge *next;
} Vertex;

typedef struct {
    Vertex *vertex[N];
    int degree[N];
    int nvertices;
    int nedges;
    bool directed;
} Graph;

void initialize_graph(Graph **g, bool directed) {
    int i;

    (*g)->nvertices = 0;
    (*g)->nedges = 0;
    (*g)->directed = directed;

    for (i = 0; i < N ; i++) { 
        (*g)->degree[i]=0;
        (*g)->vertex[i]=NULL;
    }
}

void insert_edge(Vertex *v, Edge *e) {
    e->next = v->next;
    v->next = (struct Edge*) e;
}

void create_link(Graph **g, int x, int y, int weight, bool directed) {
    Vertex *v;
    Edge *e;
    if (!(*g)->vertex[x]) {
        v = malloc(sizeof(Vertex));
        if (!v) return;
        v->x = x;
        (*g)->vertex[x] = v;
        (*g)->nvertices+=1;
    } else v = (*g)->vertex[x];

    e = malloc(sizeof(Edge));
    e->y = y;
    e->weight = weight;
    insert_edge(v, e);

    if (!directed) 
        create_link(g, y, x, weight, true);
    else 
        (*g)->nedges+=1;
}

void print_graph(Graph *g) {
    int i;
    Vertex *v;
    Edge *e;

    for (i=0; i<g->nvertices+1; i++) {
        v = g->vertex[i];
        if (v) {
            printf("Vertex %d: ", v->x);
            for (e = (Edge*) v->next; e; e = (Edge*) e->next) 
                printf(" %d(%d)", e->y, e->weight);
            printf("\n");
        }
    }
}


/* 1-----2---3 */
/* | ___/|   | */
/* |/    |   | */
/* 5-----4---+ */
int main() {
    Graph *g = malloc(sizeof(Graph));
    initialize_graph(&g, false);
    create_link(&g,1,2,1,false);
    create_link(&g,1,5,1,false);
    create_link(&g,2,5,1,false);
    create_link(&g,2,4,1,false);
    create_link(&g,2,3,1,false);
    create_link(&g,3,4,1,false);
    create_link(&g,4,5,1,false);
    print_graph(g);
    return 0;
}