关于图的问题

int nextadj(AdjMatrix G, int u, int v,int *pre)
{
    int i;
    for (i = v; i < G.vexnum; i++)
        if(G.arcs[u][i].adj != 0 && pre[i] == -1)
            return i;
    return -2;
}

int firstadj(AdjMatrix G, int u, int *pre)
{
    int i;
    for (i = 0; i < G.vexnum; i++)
        if(G.arcs[u][i].adj != 0 && pre[i] == -1)
            return i;
    return -2;
}

void DFS_path(AdjMatrix G, int u, int v, int * pre)
{
    int j;
    for(j = firstadj(G, u, pre); j >= 0; j = nextadj(G, u, j, pre))
        if(pre[j] == -1 )
        {
            if(j == v)   
            {
                print_path(v, pre);
                pre[v] = -1;
                //return ;
            }
            else {DFS_path(G, j, v, pre);}
        }
}

void all_path(AdjMatrix G, int u, int v)
{
    //寻找两点之间所有路径
    int *pre;
    int i;

    pre = (int *)malloc(sizeof(int));
    for (i = 0; i < G.vexnum; i++)
        pre[i] = -1;
    pre[u] = u;
    DFS_path(G, u, v, pre);
    free(pre);
}
void print_path(int v, int *pre)
{
    int i, j;

    for(j = 0; j < 11; j++)
    printf("  %d  ",pre[j]);
    getch();
    printf("\n");
    for(i = v; pre[i] != i; i = pre[i])
        printf("%d<--",i);
    printf("%d\n", pre[i]);
    printf("\n路线相反\n");
}