Initializing an array of pointers in C++

Question

I have a pretty specific data structure issue that I cannot figure out. For my assignment, I must have a dynamically allocated array of structures in my private section of my header. So, up to this point, in my header file, I have

struct node{
  int name;
  node *next;};  

In my private, I have

node *adj;

which is, at least to my knowledge, how you would set up having the array.
Then, in my .cpp file, I have

adj = new node*[];

This is throwing a bunch of errors. But, when I have

node *adj[n];

in my cpp and nothing in my header, it works. My questions is how do I have an array in my private section of my header, but dynamically allocate the space in my .cpp?

Answer 1

You have defined

node *adj;

which is a pointer to a node, or an array of nodes. If you want an array of pointers to nodes, you should declare

node **adj;

which is a pointer to a pointer to a node, or an array of pointers to nodes. In the first case, you allocate the array using

adj = new node[n];

which defines an array of nodes. and in the second you use

adj = new node*[n];

which defines an array of node pointers.

adj = new node*[];

should not make sense as it does not tell the compiler how big to make the array.