Question

I’m creating a Linked List program and I currently have this method to insert an item into the front of the list:

template <class T>
void LinkedList<T>::insert(T *o)
{
    node newNode;
    newNode.o = o;
    newNode.next = first;
    newNode.prev = NULL;
    first->prev = &newNode;
    first = &newNode;
}

where I have a struct as follows:

struct node {
node   *next;
node   *prev;
T      *o;
};

I think my logic is right for the insert method; however, I feel as if I’m not doing it properly, specifically dealing with the pointers. I feel as if I have to many newNode. lines and that I could do this better somehow. Any suggestions or is it right?

Note: I’m new to C++ so please be kind. I know this is a simple question

Answer 1

newNode is local to insert() and will be destructed when that method returns, meaning first->prev and first will be pointing to a node that no longer exists.

Use new:

template <class T>
void LinkedList<T>::insert(T *o)
{
    node* newNode = new node;
    newNode->o = o;
    newNode->next = first;
    newNode->prev = NULL;
    first->prev = newNode;
    first = newNode;
}