Initialize a pointer to a class with NULL values

Question

I am tring to intialize an array of pointers to a NODE struct that I made

struct Node{
    int data;
    Node* next;
};

the private member of my other class is declared as

Node** buckets;

It is currently initialised as buckets = new Node*[SIZE]

Is there anyway to initialize the array so that its members point to NULL or some other predefined Node pointer?

EDIT: Im looking for a means to initilize it without trying to generate a for loop to traverse through the full lenght of the array. The size of the array is determined at runtime.

EDIT 2: I tried std::fill_n(buckets, SIZE_OF_BUCKET, NULL); but the compiler gives the error "cannot convert from 'const int' to 'Node *'" I am using visual studio 2008. Is there something wrong that I am doing?

Answer 1

If you mean by array your array-of-pointers buckets, then yes. Just set buckets = NULL.

Edit: based on your question edit, just use memset.

memset(buckets, 0, NUM_ELEMENTS_IN_BUCKETS*sizeof(Node*));

Answer 2

First of all, the simplest solution is to do the following:

Node** buckets = new Node*[SIZE]();

As litb previously stated, this will value initialize SIZE pointers to null pointers.

However, if you want to do something like Node **buckets and initialize all of the pointers to a particular value, then I recommend std::fill_n from <algorithm>

Node **buckets = new Node*[SIZE];
std::fill_n(buckets, SIZE, p);

this will set each Node*' to p after allocation.

In addition, if you want the Node to have sane member valuesupon construction, the proper way is to have a constructor. Something like this:

struct Node {
    Node() : data(0), next(NULL){}
    Node(int d, Node *n = NULL) : data(d), next(n) {}

    int data;
    Node* next;
};

That way you can do this:

Node *p = new Node();

and it will be properly initialized with 0 and NULL, or

Node *p = new Node(10, other_node);

Finally, doing this:

Node *buckets = new Node[N]();

will construct N Node objects and default construct them.