Concerning Graph Part VII Digrap

We give the impl of digraph in this post:

#include "linked_list_bag.c"
#include "out.c"
#ifndef DIGRAPH
#define DIGRAPH
typedef struct DigraphStruct {
    int v;
    int e;
    LinkedListBag *adj;
}*Digraph;

Digraph DigraphCreateV(int v) {
    Digraph dg = (Digraph)malloc(sizeof(*dg));
    dg->v = v;
    dg->e = 0;
    dg->adj = (LinkedListBag*)malloc(v * sizeof(LinkedListBag));
    for (int i = 0; i < v; i++) { *(dg->adj + i) = LinkedListBagCreate(); }
    return dg;
}

void DigraphAddEdge(Digraph dg, int v, int w) {
    if (dg == NULL) return;
    LinkedListBagAdd(dg->adj[v], w);
    dg->e++;
}

Digraph DigraphCreate(int v, int e, int a[]) {
    Digraph dg = DigraphCreateV(v);
    for (int i = 0; i < e; i++) { DigraphAddEdge(dg, *(a + 2 * i), *(a + 2 * i + 1)); }
    return dg;
}

/**
 * examle:
 * 3 //number of vetices
 * 3 //number of edges
 * 1 0
 * 1 2
 * 2 1
*/
Digraph DigraphCreateFromInput() {
    int v, e, *a;
    scanf("%i%i", &v, &e);
    a = (int*)malloc(2 * e * sizeof(*a));
    for (int i = 0; i < e; i++) { scanf("%i%i", a + 2 * i, a + 2 * i + 1); }
    Digraph dg = DigraphCreate(v, e, a);
    free(a);
    return dg;
}

int* DigraphAdj(Digraph dg, int v, int *n) { return dg == NULL ? NULL : LinkedListBagItems(dg->adj[v], n); }

Digraph DigraphReverse(Digraph dg) {
    if (dg == NULL) return NULL;
    Digraph rdg = DigraphCreateV(dg->v);
    for (int v = 0; v < dg->v; v++) {
        int n = 0;
        int *adj = DigraphAdj(dg, v, &n);
        for (int w = 0; w < n; w++) { DigraphAddEdge(rdg, w, v); }
    }
    return rdg;
}

void DigraphRelease(Digraph dg) { 
    if (dg != NULL) {
        for (int i = 0; i < dg->v; i++) { LinkedListBagRelease(dg->adj[i]); }
        free(dg); 
    }
}

void DigraphPrint(Digraph dg) {
    if (dg != NULL) {
        printf("%i vertices, %i edges\n", dg->v, dg->e);
        for (int i = 0; i < dg->v; i++) {
            printf("%i: ", i);
            int n = 0;
            int *adj = LinkedListBagItems(dg->adj[i], &n);
            if (adj != NULL) {
                printa(adj, n);
                free(adj);
            } else {
                printf("\n");
            }
        }
        printf("\n");
    }
}
#endif